Section 1 - Introduction

Section 2 - Alternatives

Section 3 - Affected Environment

Section 4 - Environmental Effects of Alternatives

Section 5 - Compliance With Applicable Environmental Laws and Regulations

Section 6 - Coordination, Consultation, and Public Involvement

Section 7 - List of Preparers

Section 8 - Distribution List

Section 9 - Glossary and Acronyms

Section 10 - References

Figure ES-1	DMMP/EIS Plan Formulation Process
Figure ES-2	Cross Section of the Phased Development Disposal Technique for Creating Shallow Water Habitat
Figure ES-3	Shallow Water Sediment Placement Technique Using a Bottom Dump Barge
Figure ES-4	Disposal Site Selection Decision Tree
Figure 2-1	DMMP/EIS Plan Formulation Process
Figure 2-2	Schematic Comparison of Navigation Channel Maintenance Dredging and Flow Conveyance Dredging
Figure 2-3	Shallow Water Disposal - Bottom Dump Process
Figure 2-4	Shallow Water Disposal - Drag Beam Contouring Process
Figure 2-5	Joso Dredged Material Disposal Site
Figure 2-6	Lower Granite Reservoir - In-Water Disposal Areas
Figure 2-7	Disposal Site Selection Decision Tree
Figure 2-8	Cross Section of the Phased Development Disposal Technical for Creating Shallow Water Habitat
Figure 3-1	Typical Anadromous Salmonid Migration Windows
Figure 3-2	Project Area 1990 Census Tract Data: Percent Inhabitants Living in Poverty
Figure 3-3	Project Area 2000 Census Tract Data: Percent Minority Inhabitants
Figure 3-4	Aesthetics of the Study Area

Plate 1	Study Area
Plate 2	McNary Dam and Reservoir: RM 289 - 298
Plate 3	McNary Reservoir: RM 299 - 310
Plate 4	McNary Reservoir: RM 310 - 321
Plate 5	McNary Reservoir: RM 322 - 329
Plate 6	McNary Reservoir: RM 330 - 341
Plate 7	McNary Reservoir: RM 342 - 352
Plate 8	Ice Harbor Dam and Reservoir: RM 9 - 22
Plate 9	Ice Harbor Reservoir: RM 21 - 35
Plate 10	Lower Monumental Dam and Reservoir: RM 34 - 49
Plate 11	Lower Monumental Reservoir: RM 48 - 61
Plate 12	Little Goose Dam and Reservoir: RM 60 - 74
Plate 13	Little Goose Reservoir: RM 73 - 87
Plate 14	Little Goose Reservoir: RM 84 - 99
Plate 15	Lower Granite Dam and Reservoir: RM 99 - 116
Plate 16	Lower Granite Reservoir: RM 114 - 128
Plate 17	Lower Granite Reservoir: RM 127 - 147
Plate 18	3-Foot Levee Raise

Table ES-1	Comparison of Alternatives
Table ES-2	Environmental Effects Summary Matrix
Table 1-1	History of Dredging in Lower Snake River and McNary Reservoirs
Table 1-2	Comparison of Alternatives
Table 2-1	Measures Addressing Program Purposes
Table 2-2	Cost Sharing of Beneficial Use of Dredged Material
Table 2-3	Evaluation Criteria
Table 2-4	Average Annual Costs
Table 2-5	Measures Removed From Further Consideration in This DMMP/EIS
Table 2-6	Comparison of Alternatives
Table 2-7	Dredging Options by Area
Table 2-8	Environmental Effects Summary Matrix
Table 2-9	Final Alternative Evaluation Matrix
Table 2-10	Estimated Dredging Cycles and Dredged Material Volumes Per Cycle
Table 3-1	Recreation Facilities in the Lower Snake River and McNary Reservoirs
Table 3-2	Recreation Facility Visitation Lower Snake River Reservoirs, FY 95 - FY 97
Table 3-3	Study Area Population by County
Table 3-4	Study Area 1997 Employment by County
Table 3-5	Study Area Income by County
Table 3-6	Percent Poverty of Project Area Census Tracts 1990
Table 3-7	Percent Minorities in Project Area Census Tracts 2000
Table 3-8	Inventory of Commercial Facilities on the Columbia and Snake River Reservoirs Above McNary
Table 3-9	Projected Commodity Growth for Shipments Above McNary (1,000 Tons)
Table 3-10	Key Highways and Roadways
Table 3-11	Water Quality Standards in Oregon, Idaho, and Washington
Table 3-12	Test Description and Method
Table 3-13	Lower Granite Tailrace Temperature Data for Water Year 2000
Table 3-14	Ice Harbor Tailrace Temperature Data for Water Year 2000
Table 3-15	Snake River at Anatone, Temperature Data for Water Year 2000
Table 3-16	McNary Tailrace Temperature Data for Water Year 2000
Table 3-17	Clearwater River at Spalding, Temperature Data for Water Year 2000
Table 3-18	Percent of Sample by Grain Size (ASTM Standard Sieve)
Table 3-19	Elutriate Results With Background Values
Table 3-20	National Ambient Air Quality Standards
Table 3-21	Weighted Sound Levels and Human Response
Table 4-1	Environmental Effects Summary Matrix
Table 4-2	Quantification of Three Water Depth Habitats in Lower Granite Reservoir, Snake River (SR) and Clearwater River (CF) During the Early- to Mid-1980s
Table 7-1	List of Preparers - U.S. Army Corps of Engineers, Walla Walla District
Table 7-2	List of Preparers - Consultant Team

Appendix A - Hydrologic Analysis
Appendix B - Cost Estimates
Appendix C - Economic Analysis
Appendix D - Upland Disposal Conceptual Design
Appendix E - Levee Modification/Extension Analysis
Appendix F - Endangered Species Act Consultation for Anadromous Fish Species
Appendix G - Endangered Species Act Consultation for Non-Anadromous Fish and Terrestrial Species
Appendix H - Water and Sediment Quality
Appendix I - Section 404(b)(1) Evaluation
Appendix J - Dredged Material Evaluation Framework
Appendix K - Aquatic Resources
Appendix L - Cultural Resources (Deleted - Detailed Cultural Resources Information is Presented in this Final DMMP/EIS)
Appendix M - Monitoring Plan
Appendix N - Dredging Proposed for Winter 2002-2003
Appendix O - Response to Comments on the Draft DMMP/EIS

INTRODUCTION

The U.S. Army Corps of Engineers' Walla Walla District (Corps) is responsible for maintenance of the portion of the Columbia-Snake River inland navigation waterway that includes the Ice Harbor, Lower Monumental, Little Goose, and Lower Granite reservoirs on the Snake River, and McNary reservoir on the Columbia River. The Corps maintains a 14-foot- [4.3-meter (m)-] deep and 250-foot- (76.2-m) wide navigation channel through these reservoirs, which have historically required some level of dredging. These reservoirs are part of an inland navigation system that provides slackwater navigation from the mouth of the Columbia River near Astoria, Oregon, to port facilities on the Snake and Clearwater Rivers in Lewiston, Idaho, and Clarkston, Washington.

The Corps, in cooperation with the U.S. Environmental Protection Agency (EPA), is developing a long-range plan for the maintenance of the navigation channel from Lower Granite through McNary reservoirs (see plate 1). The Corps has completed a Draft Dredged Material Management Plan and Environmental Impact Statement (DMMP/EIS) for McNary reservoir and the lower Snake River reservoirs. The DMMP/EIS evaluates the likely environmental effects of the plan alternatives on a long-term, programmatic basis. Public comments on the plan and EIS will be considered by the Corps prior to the selection and implementation of a final plan. In addition, as specific proposals to implement the plan are developed and evaluated by the Corps over the 20-year term of the DMMP, the Corps will solicit public comments on these specific proposals. This Executive Summary presents the key components of the Corps' programmatic plan for:

• Maintenance of the authorized navigation channel in the lower Snake River reservoirs between Lewiston, Idaho, and Columbia River in the McNary reservoir for 20 years after the Record of Decision (ROD) is signed.

• Maintenance of limited public facilities within the reservoirs, such as recreational boat basins and irrigation intakes for the wildlife habitat management units (HMUs).

• Management of dredged material from these reservoirs.

• Maintenance of flow conveyance capacity at the most upstream extent of the Lower Granite reservoir for the remaining economic life of the project (to year 2074).

Plates 2 through 17 provide further information on area features and likely dredging and disposal areas. Based on current information, the plates depict the sites most likely to be dredged. Not every location shown will be dredged and not every location to be dredged is necessarily shown on the plates. The size and shape of the areas are approximate and will be further defined when the need to dredge is identified. This Executive Summary presents a description of the DMMP planning process, including: the purpose and need; the plan alternatives; the anticipated environmental effects of the plan alternatives; and the Corps' preferred alternative.

AUTHORITY

The portion of the Columbia-Snake Rivers navigation system addressed in the DMMP was authorized by Section 2 of the River and Harbor Act of 1945 (Public Law 79-14, 79th Congress, 1st Session) and approved March 2, 1945, in accordance with House Document 704, 75th Congress, 3rd Session. The projects include:

• McNary Lock and Dam (McNary) - Lake Wallula, Columbia and Snake Rivers, Oregon and Washington

• Ice Harbor Lock and Dam (Ice Harbor) - Lake Sacajawea, Snake River, Washington

• Lower Monumental Lock and Dam (Lower Monumental) - Lake Herbert G. West, Snake River, Washington

• Little Goose Lock and Dam (Little Goose) - Lake Bryan, Snake River, Washington

• Lower Granite Lock and Dam (Lower Granite) - Lower Granite Lake, Snake River, Washington and Idaho

Each of these projects is authorized to provide slackwater navigation, including locks and a 14-foot- (4.3- m-) deep channel. Additionally, although not part of the DMMP/EIS, each project is authorized to provide hydroelectric power generation, irrigation, recreation, and wildlife habitat.

The Corps study was initiated under guidance provided in Engineer Circular (EC) 1165-2-200, Policy - Dredged Material Management Plans, which directed the development of DMMP's for Federal navigation projects. It is the Corps' policy to manage dredged material associated with the construction or maintenance dredging of navigation projects in a manner that is the least costly, is consistent with sound engineering practice, and meets Federal environmental standards. Guidance for developing DMMP's has now been incorporated into the current revision of Engineer Regulation (ER) 1105-2-100, Planning Guidance Notebook. The ER 1105-2-100 also provides the requirements, as well as principles and guidelines, for conducting planning studies within the Corps' Civil Works program and ensuring environmental compliance through the planning process. Section 3-2 of ER 1105-2-100 provides specific guidance on the maintenance of navigation projects and the preparation of DMMP's. A least-cost alternative that is compliant with environmental laws forms the "base plan," against which other plan alternatives can be compared. Through the DMMP planning process, the Corps has considered a range of management strategies (including approaches to reduce the need for dredging and to beneficially use dredged materials) and has incorporated these strategies into its alternatives development and evaluation process.

In addition, on May 4, 1995, the Corps Director of Civil Works provided guidance to the Commander, North Pacific Division, by memorandum entitled "Lower Granite Lock and Dam, Washington, Sedimentation Studies Related to the Level of Protection Provided to the City of Lewiston, Idaho." This memorandum discussed a study to evaluate restoring the performance of project levees constructed to protect Lewiston, Idaho, from inundation caused by the Lower Granite project. It states, "The study should evaluate a range of alternative risk management plans, including modifications in the operation of the project and increased dredging." In compliance with this memorandum, consideration of reestablishing the flow conveyance capacity at Lewiston, Idaho is included in the DMMP.

PURPOSE AND NEED

The purpose of the DMMP is threefold:

1. To develop and evaluate alternative programs to maintain the authorized navigation channel and certain publicly owned facilities in the lower Snake River and McNary reservoirs for the next 20 years;

2. To develop and evaluate alternative measures to maintain the flow conveyance of the Lower Granite reservoir for the remaining economic life of the project (through 2074);

3. To develop and evaluate alternative programs of managing dredged material in a cost-effective, environmentally acceptable, and, wherever possible, beneficial manner.

The Corps is authorized to maintain a navigation system on the lower Snake and Columbia Rivers and to manage the lock and dam/navigation projects (generally referred to as "projects" or "reservoirs" in this document) on the lower Snake River from Lewiston, Idaho, to the McNary Lock and Dam project at Umatilla, Oregon, on the Columbia River (which includes the confluence of the Columbia and Snake Rivers). The Corps also maintains publicly owned recreational areas (such as marinas and swimming beaches), irrigation intake facilities for wildlife HMUs and recreation areas, and port access channels within the lower Snake River and McNary reservoirs. Historically, the Corps has dredged accumulated sediments from the navigation channel and the other facilities noted above on these reservoirs in order to maintain their operational capacities. Maintenance dredging actions are in response to a variety of conditions including, but not limited to: emergency situations which would result in an unacceptable hazard to navigation; program periodic dredge maintenance of known persistent shoal areas which impede navigation; and removal of sediment that presents a hydraulic flow impediment.

In addition, sediment accumulation in the upstream reach of Lower Granite reservoir at the confluence of the Clearwater and Snake Rivers has reduced the flow conveyance capacity of the river channel. If allowed to continue, this sedimentation would reduce the flow capacity to a point that the Standard Project Flood [(SPF) an estimated or hypothetical flood that might be expected from the most severe combination of weather and flow conditions that are considered reasonably characteristic of the geographical area] could potentially overtop the levees in Lewiston, Idaho, before the end of the economic life of the project is reached in 2074. To date, dredging has been the method of choice for the removal of this sediment and restoration of the flow capacity.

LOCAL SEDIMENT MANAGEMENT GROUP

A Local Sediment Management Group (LSMG) has been formed, and has met on three occasions (July 2000, February 2001, and December 2001) to provide input and discussion in the development of the DMMP, as well as during the plan's implementation (i.e., the dredging and dredged material management activities). This group has been formed consistent with the inter-agency National Dredging Team's guidance. Roles within the LSMG will continue to develop in accordance with policies and procedures currently evolving for the Regional Dredging Team (RDT), as referred in the April 26, 2002 policy letter jointly signed by Brigadier General David A. Fastabend (Corps of Engineers Northwest Division Commander) and L. John Iani (EPA Region 10 Administrator).

The LSMG would assist in the development and adoption of appropriate method(s) for management of dredging and use and/or disposal of dredged material from Federal navigation and maintenance projects and dredging activities regulated under Section 404 of the Clean Water Act. In the formulation of these management policies, the LSMG would be asked to consider key environmental laws and regulations involved in this process; consider the responsibilities of other Federal, state, and local resource agencies; and help develop a coordination process for dredging and beneficial use of dredged material. In addition, the LSMG would assist the Corps in evaluating dredging and dredged material management activities and options consistent with an adaptive management approach.

The general objectives of the LSMG are to:

• Provide an interagency approach to dredged material management.

• Promote consistency in dredging and sediment management activities.

• Assist in development of monitoring plans and a sediment sampling and testing framework.

• Facilitate adaptive management and beneficial use of dredged materials.

• Promote consideration of all environmental laws and regulations.

• Consider necessary cultural resource protection.

• Discuss and evaluate possible strategies to reduce sediments entering the lower Snake River system.

• Involve other stakeholder groups and pursue consistency with their plans.

The Corps anticipates that the LSMG will convene regularly, either annually or semi-annually, depending on dredged material management activities. It is envisioned that the LSMG will consider proposed dredging within a given timeframe, suggest strategies to reduce dredging requirements, provide suggestions for promising beneficial uses of dredged materials, and comment on proposals for in-water habitat creation using dredged materials. The LSMG would also serve as a forum for providing suggestions to the Corps on improving the implementation of the DMMP.

As situations develop which call for maintenance dredging, the LSMG would be informed. The situations expected to cause maintenance dredging could include, but would not be limited to:

• Emergencies involving shoaled areas that pose a serious risk to navigation of commercial vessels as indicated by records of groundings, complaints by shippers, and/or condition surveys of the navigation channel.

• Programmed/periodic dredge maintenance activities based on well-established historical records of persistent shoaling in a navigation channel that could pose a serious risk to navigation of commercial vessels.

• Shoaled areas that pose a serious risk to navigation and moorage of recreational craft as indicated by comments of operators of recreational boat facilities and/or condition surveys.

• Sedimentation to irrigation intakes associated with Lower Snake River Habitat Management Units (HMU) which restricts the ability to deliver irrigation water to the HMU.

• Advanced maintenance, of a commercial navigation channel or berth which historically requires dredging to remove shoals that pose a serious risk to navigation, when an opportunity to meet a specific environmental restoration need for beach nourishment exists and/or when the dredging can be combined with other maintenance dredging to lower the cost and minimize the dredge related disturbance to transportation and local business activities.

Federal and state agencies with resource management and regulatory responsibilities applicable to the development and implementation of the DMMP, and affected Native American Tribes, have been asked to participate in the LSMG. Additionally, public ports within the study area have been invited to participate in the LSMG. Other local entities (e.g., counties, municipalities, environmental groups, and transportation and industrial interests) with an interest in management of the resources involved in dredging and disposal activities have been invited to participate.

The LSMG has been identified as a forum for discussion of possible measures to reduce sedimentation in the lower Snake River system and, as such, land management and conservation agencies like the U.S. Forest Service, the Natural Resources Conservation Service, and others that may have a role in sediment reduction strategies, will be asked to participated in the LSMG.

ALTERNATIVES

The Corps of Engineers' planning guidelines and the National Environmental Policy Act require the consideration and analysis of a broad range of alternatives in the development of the DMMP/EIS. A summary of the process the Corps employed to develop and evaluate plan alternatives is illustrated in figure ES-1.

 

Figure ES-1. DMMP/EIS Plan Formulation Process

Plan Measures Development and Evaluation

Initially, a broad range of measures that either partially or completely fulfilled the purpose and need were considered in the development of plan alternatives. These measures included:

• Sediment deposition reduction.

• Dredging.

• Management of dredged materials.

• Raising levees in the Lewiston, Idaho, area.

In accordance with the requirements of the NEPA, a broad range of alternatives that could potentially meet the stated purpose and need was developed. The Corps conducted public scoping meetings, consulted with state and Federal environmental and resource agencies, and conducted technical studies to develop a range of conceptual alternatives that addressed the plan's purpose and need. Multiple scenarios which included sediment deposition reduction, dredging, dredged material management, and/or levee raises were considered in the development of plan measures. A range of alternative strategies within each of the plan measures was developed and evaluated.

Sediment deposition reduction strategies that were considered included: changes in upstream land uses to control sediments entering the system; pool draw-down; in-water sedimentation controls that would prevent sediments from being deposited within the navigation channel, including Bendway weirs and "bubble curtains" around the navigation channel; and construction of upstream sediment traps.

Dredging scenarios included maintenance dredging only on an as-needed basis, dredging 300,000 cubic yards (cy) [229 366.5 cubic meters (m³)] per year, dredging 1,000,000 cy (764 555 m³) per year, and dredging 2,000,000 cy (1 529 110 m³) per year. The three scenarios that included dredging beyond navigation maintenance requirements were intended to provide flow conveyance capacity in Lower Granite reservoir.

Similarly, several levee raise alternatives in the Lewiston, Idaho, area were considered. These included: 3-foot, 4-foot, 8-foot, and 12- foot (0.9-m, 1.2- m, 2.4- m, and 3.7- m) levee raise options.

Finally, a range of dredged material management options were developed and evaluated. These options included upland disposal of dredged material, in-water disposal of dredged material, and beneficial uses of dredged material. Several in-water disposal options were considered, such as beneficially using dredged sand and gravel to create shallow-water fish habitat.

The Corps may need to perform dredging on an emergency basis. Potential situations that could require emergency dredging include high flows depositing sediment that block the navigation channel or rock could be swept into the navigation lock approach posing an unacceptable navigation hazard. For an emergency dredging situation, the Corps would perform environmental coordination on an expedited basis as much as possible before initiating the emergency dredging.

An iterative screening process was developed that consisted of formulating alternatives from the most viable program measures above, evaluating each alternative and selecting alternatives for further detailed consideration. Preliminary evaluation criteria were then developed to determine the alternatives that were feasible, reasonable, and should be considered in detail. These criteria considered whether:

• The alternatives were cost-effective, while either providing environmental benefits or causing the least environmental damage.

• The alternatives provided a way to regain and/or maintain channel capacity to provide an acceptable level of flow conveyance capacity resulting in flood protection (based on the results of a risk-based analysis) in the Lewiston-Clarkston area.

• The alternatives have acceptable impacts on other project uses (such as shippers and recreational users).

Based on these preliminary screening criteria, measures that were incorporated into plan alternatives included combinations of dredging and levee raises, with consideration of upland disposal/beneficial use and in- water disposal/beneficial use of dredged materials.

A set of more detailed screening criteria were then developed to evaluate the relative impacts, costs, and/or benefits of a set of dredging and levee alternative combinations. Application of these criteria facilitated the identification of alternatives that were considered feasible, reasonable, and would be evaluated in detail. The identified alternatives are summarized in table ES-1 and presented in detail below:

Alternative 1 - No Action (No Change) - Maintenance Dredging With In-Water Disposal

Alternative 1 represents the continuation of historic maintenance of the authorized navigation channel in the study area. As such, this alternative includes those activities (specifically, mechanical dredging and in-water disposal) that have been performed in the recent past to maintain the authorized depths in the navigation channels of the lower Snake River and McNary reservoirs. The areas covered include Lake Wallula behind McNary Lock and Dam on the Columbia River and the reservoirs behind Ice Harbor, Lower Monumental, Little Goose, and Lower Granite on the lower Snake River (see plates 2 through 17). This navigation project provides for a 14- foot by 250- foot (4.3-m by 76.2- m) channel within each reservoir with at least a 15-foot (4.6-m) depth over the sills at each of the locks. This alternative would provide the authorized navigation clearance and provide some flow conveyance capacity in Lower Granite reservoir, based on maintenance dredging. Maintenance dredging would be done on an as-needed basis (possibly as often as every 2 to 3 years) and would generate up to 340,000 cy (259 948.7 m³) per dredging activity. Additionally, dredging could only occur during an in-water work "window" approved by the National Marine Fisheries Service (NMFS). This window represents the time of year when dredging and disposal activities would have minimal effects on salmonid species. The current in-water work window is December 15 through March 1 for the lower Snake River reservoirs and December 1 to March 31 for the Columbia River. The Corps also periodically conducts maintenance dredging around public recreation areas (such as swimming beaches and boat basins) and irrigation intakes for wildlife HMU's managed by the Corps (see plates 2 through 17).

Disposal of dredged materials under alternative 1 would be consistent with disposal methods utilized during recent dredging cycles: dredged materials would be loaded onto bottom-dump barges and transported to the disposal site. Dredged materials would be sampled for particle size and sediment quality prior to dredging. Historic testing for sediment quality has indicated that dredged sediments are suitable for in-water disposal. As such, fine- grained materials (i.e., silts) would be disposed in deep-water areas and sand, gravel, and cobbles would be used to create shallow-water fish habitat within the study area reservoirs (using techniques similar to those in alternative 2, described below).

Alternative 2 - Maintenance Dredging With In-Water Disposal to Create Fish Habitat and a 3-Foot (0.9-m) Levee Raise

This alternative considers the same dredging activities with the same quantities and frequencies as alternative 1, but with changes in dredging methods, work window, and disposal location for silt. Mechanical dredging would still be the primary dredging method used, but hydraulic dredging would also be considered for off-channel areas on a case-by-case basis. The majority of the dredging would be done during the winter in- water work windows used in alternative 1, but a summer work window would be considered for off-channel areas on a case-by-case basis. Silt would no longer be disposed of in deep-water sites. Instead, all dredged materials would be placed in water to create shallow-water fish habitat that would be beneficial to salmonid species.

Disposal and creation of shallow-water habitat would be accomplished using bottom-dump barges to transport and deposit the dredged material. Finer sands and silts would be used in a base for creation of habitat and may be dumped in mid-depth water areas as part of this process. Coarser sands, gravels, and cobbles would be placed over the base or within shallow water. These materials provide a favorable substrate for juvenile salmonid rearing and resting. Finally, a drag beam or some other similar device would be used to re-contour the surface of the material dumped from the bottom-dump barges in order to provide a relatively smooth surface. Placement and contouring of sand and gravel would occur with each dredging cycle in order to maximize the amount of habitat created. Figures ES-2 and ES-3 illustrate this dredged material management process.

 
Figure ES-2. Cross Section of the Phased Development Disposal Techniques for Creating Shallow Water Habitat

 
Figure ES-3. Shallow Water Sediment Placement Technique Using A Bottom Dump Barge

An upland containment area would be constructed for disposal of dredged materials that sediment testing indicates would be unsuitable for in-water disposal but suitable for upland disposal. These dredged materials would be transported by barge to the upland disposal site. Currently, the preferred site is the Joso HMU, located on land adjacent to the Lower Monumental reservoir at Snake River Mile 56.5 (see plate 11). Only material that meets all applicable environmental health and safety regulations and requirements would be disposed of at the upland site. Material that is not appropriate for disposal at the upland site would be transported to a licensed landfill facility.

Alternative 2 would employ an "adaptive management" approach to the overall implementation of the DMMP. The Local Sediment Management Group (LSMG) would provide input and feedback to the Corps with respect to dredging and dredged material management that would be implemented under this alternative, as well as Alternatives 3 and 4. The adaptive management approach would allow the Corps and the LSMG to regularly evaluate dredging and dredged material management activities and monitoring results, and make needed adjustments to the overall course of action.

This alternative includes raising the levee at Lewiston up to 3 feet (0.9-m) at critical locations to maintain flow conveyance. Plate 18 shows the location of proposed levee raises. Proposed levee raises would require modification of portions of two adjacent roadways. Three existing buildings would experience an increased risk of flooding.

Alternative 3 - Maintenance Dredging With Upland Disposal and a 3-Foot (0.9-m) Levee Raise

This alternative considers the same dredging activities in terms of locations, quantities, frequencies, and methods as alternatives 1 and 2, but with upland disposal of dredged material. The 3-foot (0.9-m) levee raise described as a part of alternative 2 would be included with this alternative.

Under this alternative, dredged materials would be transported by barge to the Joso upland disposal site (see plate 11). This site was selected through a process that identified and screened multiple candidate sites and selected the Joso site based on environmental and economic considerations. A large portion of the Joso site is a disturbed area that was previously used for gravel mining. An existing barge slip is located at the downstream end of the site, and this area would be used to establish an off- loading and staging area for the disposal facility. A containment berm would be constructed around the disposal area and a 600-foot (182.9-m) setback from the river would provide a buffer zone to minimize environmental impacts of disposal operations.

Alternative 4 -Maintenance Dredging With Beneficial Use of Dredged Material and a 3-Foot (0.9-m) Levee Raise

This alternative considers the same dredging activities in terms of locations, quantities, frequencies, and methods as alternatives 1, 2, and 3. As with alternatives 2 and 3, this alternative includes raising the levee at Lewiston up to 3 feet (0.9 m) at critical locations to maintain the flow conveyance capacity of the upper reservoir behind Lower Granite Dam at the confluence of the Snake and Clearwater Rivers.

The distinguishing characteristic of alternative 4 is that the primary focus of the management strategy for dredged material under this alternative would be to incorporate beneficial uses. For each dredging activity, the Corps would identify potential beneficial uses and coordinate the uses with the Local Sediment Management Group prior to selecting a use. Beneficial uses, as defined by this process, may be achieved when a local sponsor is willing to contribute a share of the cost if the use would require cost sharing.

Potential beneficial uses that could be initially considered include:

• Fish habitat creation as described in alternative 2.

• Woody riparian habitat program.

• Hanford remediation and closure activities capping material.

• Potting soil.

• Riparian habitat restoration.

• Fill at Port of Wilma.

• Fill on non-Federal lands.

• Fill for roadway projects.

The Corps proposes to use dredged material to develop woody riparian area at Chief Timothy Habitat Management Unit in Lower Granite Reservoir as a beneficial use of dredged material that would result from the planned dredging in winter 2002-2003. This beneficial use would create shoreline habitat in line with the goals of the Lower Snake River Fish and Wildlife Compensation Plan.

Because opportunities to use dredged material beneficially become available over time and cannot always be anticipated, a process would be established whereby a notice would be sent to parties known to have an interest in the use of the dredged material and a public notice published prior to the proposed dredging/beneficial use activity. Impacts would be assessed on a case-by-case basis through this process. The Corps may prepare Biological Assessments (BA's) for each dredging activity or for up to 5 years of dredging activities, depending upon the outcome of the Endangered Species Act (ESA) consultation processes with the NMFS and U.S. Fish and Wildlife Service (USFWS). The Corps may also prepare a Clean Water Act Section 404(b)(1) evaluation for each dredging activity or for 5 to 10 years of dredging, depending upon the outcome of coordination with the state water quality agencies and EPA.

ENVIRONMENTAL EFFECTS OF ALTERNATIVES

The following sections provide brief summaries of the anticipated environmental effects of the plan alternatives considered in the DMMP/EIS for each element and table ES-2 presents a summary of those effects. The anticipated effects are generally characterized with respect to their intensity and duration as:

• Direct, indirect, or cumulative;

• Minor, moderate, or major, and

• Short- or long-term.

Aquatic Resources

The dredging activity associated with all four alternatives would have the same indirect, minor, short-term effects on aquatic ecosystems by disturbing sediments and removing macroinvertebrate species (which are prey species for resident and migratory fish) from the dredging area. However, re-colonization of macroinvertebrates would occur relatively rapidly within both the dredging area and at the in-water shallow and mid-depth disposal areas. Long-term impacts would not occur. Fish could use the areas upstream and downstream of dredging and disposal activities, and dredging would not be a continuous activity confined to a single location. Fish could return to the area following completion of dredging and disposal activities.

Alternatives 1, 2, and 4 could have potential benefits by creation of in-water fish habitat, whereas alternative 3 (upland disposal) would provide no benefit to fish habitat. In addition to benefiting salmonid species, creation of in-water habitat could benefit white sturgeon and macroinvertebrate species. Initially, the proposed beneficial use would be creation of woody riparian habitat in shoreline areas of Chief Timothy HMU. The 3-foot (0.9-m) levee raise proposed in alternatives 2, 3, and 4 would have no impacts on aquatic resources.

Terrestrial Resources

The dredging and disposal actions within and adjacent to the river included in alternatives 1 through 4 would not prevent wildlife (primarily waterfowl and raptors) from obtaining food from, or otherwise using the areas adjacent to, dredging and disposal activities. Dredging and disposal activities would occur only within the approved in- water work window and, following dredging and disposal, wildlife would return to areas affected by these activities.

There would be displacement of wildlife habitat for alternative 3, where the disposal of all dredged material would occur at the Joso upland site. Most disposal activities would occur on the disturbed portion of the site that was formerly used as a gravel pit. The area would be stabilized following each disposal cycle and would be re-contoured and restored with native plantings following completion of all dredging over the next 20 years. With completion of the disposal and revegetation, the site would provide wildlife habitat similar to the surrounding area, which would be a long-term benefit to wildlife habitat. Upland disposal at Joso is expected to have a direct, long-term, moderate impact on terrestrial wildlife. Material that is unsuitable for in-water disposal under alternatives 2 and 4 would be taken to an upland site (currently identified as the Joso site), which would have a minor, direct effect on terrestrial resources at the site.

The proposed 3-foot (0.9- m) levee raise for alternatives 2, 3, and 4 would similarly have minor, indirect, temporary impacts on terrestrial species. Construction could disturb wildlife; however, the areas proposed for the levee raise are in an urban setting and only those species accustomed to human activity would be present. The levee raise would be placed atop the existing levee. Revegetation would result in habitat similar to existing conditions.

Endangered Species

The Corps prepared a Biological Assessment for the proposed dredging and dredged material management activities and consulted with NMFS and USFWS. See Appendix F and G for further details. NMFS determined that the proposed actions would not cause jeopardy to anadromous fish species listed under the Endangered Species Act (ESA) and set forth Reasonable and Prudent Measures. USFWS provided concurrence with the findings of the Corps' Biological Assessment.

Anadromous salmon and steelhead stock from all of the Evolutionary Significant Units (ESU's) listed as Threatened or Endangered under the ESA pass through the McNary reservoir and lower Snake River. These species include Snake River spring/summer chinook salmon (Oncorhynchus tshawytscha), listed as Threatened in 1991; Snake River fall chinook salmon (O. tshawytscha), listed as Threatened in 1991; Snake River sockeye salmon (O. nerka), listed as Endangered in 1992; Snake River Basin steelhead (O. mykiss), listed as Threatened in 1998; Upper Columbia River spring run chinook salmon (O. tshawytscha), listed as Endangered in 1999; Middle Columbia River steelhead (O. mykiss), listed as Threatened in 1999; and Upper Columbia River steelhead, listed as Endangered in 1997. In addition, the resident Columbia Basin bull trout (Salvelinus confluentus) is listed as Threatened under the ESA.

Of the alternatives that involve in- water disposal, alternative 1 would provide the least benefit to increasing habitat for fall chinook salmon rearing in the McNary and lower Snake River reservoirs. The dredged material disposal methods of alternative 2 would provide the greater opportunity to develop shallow water salmonid habitat throughout the McNary and lower Snake River reservoirs. Upland disposal of dredged material proposed in alternative 3 would not provide for creation of salmonid habitat. Some of the beneficial uses proposed in alternative 4 could also create salmonid habitat.

Because dredging and disposal activities would only occur dur ing authorized in-water work windows, impacts to salmonids would be minimized. For alternative 1, the work windows would be winter only. For alternatives 2, 3, and 4, these work windows would include winter main stem dredging and both winter and summer dredging of off-channel areas.

The likelihood of bull trout being in the project areas is remote, and they are not expected to be affected by the dredging and disposal activities. However, if bull trout were present in dredging and disposal areas, there would be short-term, indirect effects due to turbidity and disturbance from dredging activities, which would cause them to leave the area.

Beneficial use of dredged material proposed in alternative 4 is anticipated to have minor effects or potential benefits to endangered fish species.

The bald eagle (Haliaetus leucocephalus) inhabits the project area and is listed as Threatened under the ESA. The dredging activities proposed for all four alternatives would not be a continuous activity confined to a single location. If impacts to bald eagles were to occur, they would be minor, short-term, and localized. Adjacent areas would be available for foraging, feeding, and perching.

The levee raise proposed in alternatives 2, 3, and 4 would not result in the loss of any trees or shoreline perch areas. Eagles' prey species would not be impacted. Thus, if any impacts were to occur, they would be related to disturbance during construction and would be minor, short-term, and localized.

Two plant species that may be found within the project area [Ute ladies' tresses (Spiranthes diluvialis) and water howellia (Howellia aquatilus)] are listed as Threatened under the ESA. Another plant, Spalding's silene, is proposed for listing under the ESA.

The proposed activity would not likely impact these plant species. There are no recorded observations of Ute ladies' tresses in the project vicinity, and they are not likely to occur due to lack of suitable habitat and the elevation of the project area. Therefore, no impacts to Ute ladies' tresses are expected to occur. Similarly, water howellia and Spalding's silene are not likely to occur at this low elevation or in this habitat.

As with endangered fish species, alternative 4 is not anticipated to impact endangered terrestrial species. However, because opportunities to use dredged material beneficially become available over time and cannot always be anticipated, a process has been established whereby a notice would be sent to parties known to have an interest in the use of the dredged material and a public notice published prior to the dredging activity. Impacts would be assessed on a case-by-case basis through this process. Plant surveys would be required to determine the presence of Ute ladies' tresses. Any sites found to support these plants would need to be avoided to preclude impacts to these plants. A BA may be prepared for each dredging activity, or for 5 years of dredging activities, depending upon the outcome of the ESA consultation with USFWS.

Recreation

Dredging activities proposed as part of all of the alternatives are expected to have a minor, short-term effect on those recreation activities and facilities located near proposed dredging and disposal locations. Dredging scenarios proposed may temporarily close boat ramps and boat basins and affect public recreation areas (e.g., swimming beaches) on a short-term basis during maintenance dredging. There would be short-term, minor impacts due to low levels of activities that occur during the winter months. Summer dredging of recreation sites would also have short-term impacts since the small areas would not take long to dredge. Construction of the levee raises proposed under alternatives 2, 3, and 4 are anticipated to have short-term, direct effects on the Lewiston levees park and the recreational activities that occur there. These effects would be minor because they impose a temporary disruption of activities at the Lewiston levees park, specifically multi- use paths and day- use facilities such as picnic tables on and adjacent to the levees could not be used during construction of the levee raise. Recreational facilities and activities would be restored following the interruption caused by the construction of the levee raise.

Upland disposal activities (barging and material handling) at the Joso site would have long-term, minor, indirect effects on river users, hunters, and the nearby Lyon's Ferry State Park and Lyon's Ferry Marina facilities. These effects are anticipated to be minor since the disposal area is set back at least 600 feet (182.9 m) from the river shoreline and is not directly visible from Lyon's Ferry State Park and Lyon's Ferry Marina, which are located on the opposite side of the Snake River.

To the extent that beneficial uses of dredged material would reduce the need to dispose of the material either upland or in-water, these uses are expected to have minor, direct impacts to recreational facilities and activities, depending on where the material is placed. Beneficial uses that would create or enhance wildlife habitat would have indirect beneficial effects on recreation if they enhanced hunting, fishing, or wildlife viewing opportunities.

Cultural Resources

Proposed dredging, disposal, and levee modification activities could affect cultural resources located within the project's area of potential effect as defined under the National Historic Preservation Act (NHPA). Dredging actions for all four alternatives would be limited to the removal of accumulated sediments and would not affect original riverbed or shoreline material, or cultural resources contained within that material. In-water disposal proposed in alternatives 1, 2, and 4 could affect identified underwater cultural resources in the lower Snake River and McNary reservoirs; however, known submerged cultural resource sites would be avoided to the maximum extent practicable during the placement of dredged material. Levee modification proposed in alternatives 2, 3, and 4 would not affect any cultural resources sites that have been ident ified.

Alternatives 2, 3, and 4 would use the Joso area for the upland disposal of some or all of the dredged material. Any cultural resources identified in the vicinity of the Joso upland disposal site would be avoided during construction and operation of the disposal site.

Beneficial uses of dredged material, as proposed in alternative 4, could potentially affect cultural resources, depending on the use. Prior to implementation of any beneficial use, the Corps would need to conduct research and field investigations to determine if cultural resources would potentially be affected.

The development, implementation, and monitoring of project actions would be conducted in conformance with the NHPA and the National Environmental Policy Act. Prior to the finalization and implementation of any plan, the Corps would complete the required cultural resource consultation. The Corps would continue to consult with appropriate State and Tribal Historic Preservation Officer(s) as well as other affected consulting parties throughout the life of the 20-year plan.

If human remains were inadvertently discovered during dredging or dredged material handling operations, all work in the immediate area would stop and the Corps archaeologist will take the appropriate steps to address the discovery. The Corps will notify all appropriate tribes, agencies, and local coroner's offices depending on the status of the human remains.

Socioeconomics

Dredging to maintain the navigation channel, access channels to ports and moorages, public recreation areas, irrigation intakes for HMUs, and flow conveyance capacity of the Lower Granite reservoir proposed under all four alternatives, and disposal of dredged material in- water proposed in alternatives 1, 2, and 4 represent no change in the management of the navigation projects and associated facilities. Therefore, with respect to navigation and economic use of waterways, these alternatives would have no effects on regional population, employment, or income. All alternatives considered would have minor, short-term, positive economic effects due to added employment for dredging-related activities.

Since alternative 1 does not include a levee raise in Lewiston, allowing continued loss of levee freeboard and increased risk associated with flooding, it would be expected (in comparison to the other alternatives being considered) to have an indirect, long-term, moderate negative effect on the local economy of the Lewiston area since reduction in annualized flood damages would not be realized. Proposed levee modifications for alternatives 2, 3, and 4 are anticipated to have a direct, short-term, positive effect on the local economy of the Lewiston area due to the added jobs and materials required for construction of the levee modifications.

Upland disposal proposed under alternative 3 would be expected to have a direct, minor, short-term positive impact due to jobs created for construction and initial operation of the disposal facility at the Joso site. The economic effects would remain positive, but lessen over time, for the continued use of the upland disposal facility.

Beneficial use of dredged material would be expected to have a direct, minor, short-term positive economic effect due to construction activities associated with implementation of the beneficial use. Also, beneficial uses that create or enhance wildlife habitat or recreational resources would potentially have minor, indirect, long-term beneficial effects attributable to enhancement of recreational resources and opportunities.

The Corps reviewed demographic data to identify areas where there are potential environmental justice populations, and considered the alternatives' environmental effects with respect to these areas.

Transportation

River Navigation

Maintenance dredging for all four alternatives would have a long-term beneficial impact on river navigation by ensuring adequate depths in the navigation channels, access channels to ports and moorages, and public recreation areas. In-water disposal activities would be away from areas of commercial navigation. Dredging in the navigation channels would occur on a 2-year cycle on average, causing some disruption during the authorized in- water work period from December 15 to March 1 in the Snake River and December 1 and March 31 in the Columbia River. No disruption to recreational boating would be expected in the main river channels; only short-term disruption may occur during maintenance dredging of boat basins.

Upland disposal of all material proposed in alternative 3 would increase the number of lockages (barges passing through lock and dam facilities) during the dredging period by as much as 150 lockages every 2 years (up to 113 barges with an average of four lockages of three barge tows). These lockages would occur during a time of year when they would cause very little impact to other commercial or recreational traffic.

Alternative 4 could have different effects in the disposal area depending on the disposal location and method employed to develop the beneficial use. For the beneficial uses being considered, the adverse impacts to other river navigation would be short-term and minor. In some cases beneficial uses could have positive impacts to river navigation by providing added terminal and port areas.

Railroads

Continued maintenance of the navigation channels, access channels to ports and moorages, public recreation areas, irrigation intakes, and flow conveyance capacity proposed in all four alternatives would have no adverse effect on the railroads in the area and would continue to support the multi- modal flow of commerce to and from the study area.

The nominal 3- foot (0.9- m) levee raise, proposed in alternatives 2, 3, and 4 includes construction to the west levee below the south abutment of the Camas Prairie Railroad Bridge over the Clearwater River at Lewiston and would have minor, short-term impacts during construction.

Disposal of all dredged material at Joso proposed in alternative 3 would cause minor, long-term, direct impacts to the Union Pacific Railroad resulting from the developments of the Joso disposal site and increases in crossings of the Union Pacific Railroad right-of-way during construction.

The beneficial use of the dredged material proposed in alternative 4 would be determined on a case-by-case basis and may affect the railroads due to minor disruptions that could potentially involve the railroad to transport dredged material to a final destination point. The potential impacts to railroads from this alternative are expected to be minor.

Highways/Roadways

Modification of roads (associated with the levee raise) proposed in alternatives 2, 3, and 4 would create short-term, direct impacts to Highway 129 and the Snake River Road. The roadways would be raised to avoid inundation with water during high- flow events. Effects would occur during reconstruction of the affected portions of roadway.

One concept for beneficial use of dredged material, proposed in alternative 4, would use the material to form a roadway connection on the north shore of the Lower Granite pool linking State Route (SR) 193 at Wawawai to SR 194, a distance of 3 miles [4.8 kilometers (km)]. This would create a potential positive effect with respect to roadway construction.

Geology and Soils

Maintenance dredging proposed in all fo ur alternatives is not anticipated to significantly affect the geology and soils in areas surrounding the lower Snake River and McNary reservoirs. Dredging would cause local soil and rock disturbance and relocation of some alluvial material.

Modifications to the levee system in Lewiston proposed in alternatives 2, 3, and 4 are expected to result in direct effects on the geology and soils of the levees and surrounding areas. Minor, short-term effects to soils and topography, resulting from earthmoving and construction activities, are expected during construction of the levee modifications.

Upland disposal as proposed under alternative 3 is anticipated to have a direct, long-term effect on the soils and topography of the Joso site. Erosion and compaction would occur from construction and dredged material disposal activities. Site restoration would include stabilizing and seeding of the dredged material after it has been disposed of on site. Disposal material would be contained within a bermed area and drainage would be controlled to minimize erosion. In addition, a 600- foot (182.9- m) setback from the river would help minimize shoreline erosion.

Alternative 4 would use some or all of the dredged material for beneficial uses. Beneficial uses, such as woody riparian habitat creation, other habitat creation/enhancement, landfill cover, or other activities, would be expected to have direct, short-term impacts to the soils in the areas where the uses would be implemented.

Water Quality/Water Resources

All alternatives considered in the DMMP/EIS are expected to have a temporary, direct negative effect on water quality in the Columbia, Snake, and Clearwater Rivers, mostly because of turbidity plumes caused by the dredging and, where proposed, in- water disposal. However, it is anticipated that elevated turbidity levels would be confined and will stay within the "mixing zones" (established under Clean Water Act Section 401 water quality certification) allowed for this activity, and allowable turbidity downstream of the mixing zone would not be exceeded.

Historically, the Corps has sampled and tested dredged materials for sediment size and quality, including contaminants, to determine suitability for in-water disposal. To date, sediment contaminant levels have been at low levels that allow in- water disposal. Based on historic sediment testing data, contaminant levels that would preclude in-water disposal in the future are not anticipated. Nonetheless, the Corps will continue its sediment sampling protocols to ensure sediment quality is adequately assessed.

Construction of the levees at Lewiston proposed in alternatives 2, 3, and 4 could result in short-term, minor water quality impacts due to runoff and erosion. These concerns would be minimized with the implementation of a site-specific Erosion/Sedimentation Control (ESC) Plan and construction best management practices (BMP's). The levees would be stabilized by hydroseeding immediately after construction.

Direct, temporary, minor impacts due to erosion may occur as a result of construction and disposal operations at the Joso site as proposed in alternative 3. A containment berm would be constructed on the perimeter of the permanent disposal area and would minimize water quality impacts associated with runoff and erosion. An ESC plan would be developed and BMP's used during site development. The site would also be regularly stabilized in a phased manner during disposal, and measures will be taken to minimize sedimentation from dredged material transfer activities.

Impacts from beneficial use of the dredged material proposed in alternative 4 could vary depending on the use and would be the responsibility of the local sponsor. As with other dredged material management methods, beneficial uses involving placement of dredged materials would be subject to ESC measures and BMP's.

Wetlands

Minor, short-term, indirect impact to wetlands adjacent to the levees or roadway could occur during construction of the nominal 3- foot (0.9- m) levees as proposed in alternatives 2, 3, and 4. Long-term impacts are not expected as a result of the levee raise.

Two small wetland areas have been identified in the vicinity of the Joso upland disposal site proposed in alternative 3. The proposed disposal facility has been sited to avoid directly or indirectly affecting these wetland areas.

Beneficial uses proposed in alternative 4 would be expected to generally affect wetland resources positively if dredged material were used for enhancement or creation of aquatic and wildlife habitat. Beneficial uses could potentially improve wetland size, function, and quality. Specific wetlands in the vicinity of a proposed beneficial use would require identification prior to commitment for the beneficial use project. A wetland area approximately one acre (0.4 hectare) in area is adjacent to the area where woody riparian habitat development is proposed. This wetland area would be minimally impacted by the proposed habitat development. The wetland is a low area where ponding occurs; it holds water only at extremely high pool elevations, and dries out during most years. Under the proposed beneficial use, an inlet channel to the pond would be constructed, which should increase flows into the pond at lower reservoir elevations. It will also have an exit (outlet) constructed so there will be some flow through, thus improving the water quality.

Floodplains

There would be no foreseeable significant negative floodplain impacts as a result of the maintenance dredging proposed in all four alternatives or the levee raise at Lewiston proposed in alternatives 2, 3, and 4.

The permanent upland disposal site at Joso would not be located in the 100-year floodplain and would not affect the floodplain. Approximately 360,000 square feet (33 445.1 square meters) of the unloading and temporary storage area for dredged material would encroach on the 100-year floodplain, causing minor short-term impacts to the floodplain during the time that the material is stored. However, the fill is not expected to change the water surface elevation and would not pose long-term effects on the 100-year floodplain.

Beneficial uses are not anticipated to present significant impacts to floodplain areas. The proposed woody riparian habitat creation would involve placement of fill in shoreline areas at Chief Timothy HMU, including some areas within the 100-year floodplain. This fill would not change the water surface elevation, nor have impact on the 100-year floodplain. Specific areas considered for placement of dredged material under beneficial use would require analysis of floodplain issues.

Hazardous, Toxic, and Radioactive Waste

Based on Phase I environmental site assessments conducted for the Joso site, there is a very low potential for land-based hazardous, toxic, and/or radioactive waste concerns to be associated with the Joso upland disposal site.

Based upon existing sediment quality data, it is not anticipated that the handling and disposal of dredged materials as hazardous or solid waste (as defined by applicable environmental health and safety regulations and requirements) would be required.

The proposed woody riparian habitat creation area at Chief Timothy HMU does not pose any known HTRW concerns. Beneficial use of dredged materials could have minor positive effects on hazardous waste if dredged material was used for cover or fill at the Hanford Reservation, which is a beneficial use option considered in alternative 4. In general, beneficial uses that involve upland handling of dredged materials would not be expected to have hazardous waste effects, given the quality of the sediments. See the Water Quality/Water Resources section for information on sediment contaminant levels.

Because of the location of the Hanford Nuclear Reservation at the upstream end of McNary reservoir, there is speculation of radioactive materials being present in the reservoir sediments. Dredging activities under any of the four alternatives should not extend deep enough into the sediment layer to reach existing (if any) radioactive material. However, the Corps plans to evaluate each dredging activity in the McNary reservoir and determine if and what type of further pre-dredging sediment testing and analysis may be necessary.

Air Quality

All alternatives would cause direct, minor, short-term effects to local air quality due to dredging equipment operation. Dredged material would be wet, and is not anticipated to be subject to dust generation. Construction activities associated with raising the Lewiston levee could generate dust, as could the upland disposal at Joso proposed in alternative 3 and the upland contingency disposal at Joso in alternatives 2 and 4. The BMP's would be used to prevent material from becoming airborne during transport, offloading, and upland placement.

No additional impacts associated with implementation of alternative 4 are anticipated.

Noise

Minor, direct, short-term noise impacts are anticipated to result from dredging, transport, and disposal activities of all alternatives considered. Levee construction would occur primarily during daytime hours and would cause minor, short-term impacts from construction activities. Upland disposal of dredged material would occur primarily during daytime hours and would have minor, direct, short-term effects during site work and disposal activities.

Aesthetics

It is anticipated that all four alternatives will have a direct impact on aesthetics in the area where dredging activities are taking place and, for alternatives 1, 2, and 4, where in-water disposal is anticipated. Impacts due to levee modification as proposed in alternatives 2, 3, and 4 are expected to be both short-term (due to construction activities) and long-term (due to raising of the levees). Levee modifications would affect the riverfront park facilities and would present moderate impacts to both visual quality and viewing patterns.

Under alternative 3, dredged material from all reservoirs disposed of at the Joso site in the Lower Monumental reservoir would have a direct, long-term effect on the aesthetics of the disposal site and the areas immediately surrounding the site from which the site can be viewed. While the proposed disposal operations would directly impact the aesthetic quality of the Joso site, the effects would be minor due to the fact that the site is not highly visible to viewers and would be restored upon completion of disposal operations. Beneficial use of dredged material, proposed in alternative 4, would potentially have a long-term positive effect on aesthetic resources if used for wetlands or habitat restoration. Proposed woody riparian habitat creation at Chief Timothy HMU in Lower Granite Reservoir would have a long term, beneficial effect on the aesthetics of the shoreline area.

Native American Tribes and Communities

Impacts from DMMP activities that are of concern to tribes would involve potential effects to aquatic species and their habitats, water quality, and cultural resources. Although DMMP actions would occur in the five study area reservoirs over its 20-year life, most dredging activities and the majority of any in-water disposal would occur in the Lower Granite reservoir.

Dredging as proposed for alternatives 1, 2, 3, and 4, and in- water disposal of dredged materials as proposed for alternatives 1, 2, and 4, could result in habitat changes that are beneficial, neutral, or even detrimental to different aquatic species depending on given species responses and needs. Constructing more shallow-water habitat could change water quality factors. Shallow-water temperatures, currently below optimum for the growing season of resident game fish, would be increased and possibly enhance resident game fish habitat conditions and population numbers.

Water quality impacts from DMMP activities under any of the alternatives are expected to be temporary, but would result in direct negative effects due to turbidity plumes caused by dredging and in-water disposal. Greater sediment plumes are expected from dredging operations.

Concerns over potential impacts to cultural resources would be focused on damage to cultural sites from dredging actions or covering sites with too much sediment as a result of disposal activities. As now planned, dredging under all four alternatives would be limited to existing navigation channels and/or would not go below accumulated sediments into original riverbed. Likewise, disposal activities either upland or in- water would avoid known sites. (However, sediment drift from in- water disposal could result in the eventual covering of sites with additional material.) Such actions would help to reduce the chances of impacting cultural sites.

Cumulative Effects

The National Environmental Policy Act and the Council on Environmental Quality's regulations require Federal agencies to consider the cumulative impacts of their actions on the natural and human environment. Cumulative effects are those environmental consequences that result from the incremental impact of a proposed action when added to other past, present, and reasonably foreseeable future actions, regardless of the agencies or individuals that may undertake them.

Other past, present, and reasonably foreseeable projects or actions that could, when added to the proposed plan alternatives, result in cumulative impacts include:

• Construction of the five Corps dams.

• Land uses in the study area.

• Past and present dredging and disposal activities undertaken by the Corps for navigation maintenance or flow conveyance, as well as dredging for ports and/or boat basins within the study area.

• Levee construction and modification.

• Re-licensing of dams within the Columbia/Snake River system.

• The Lower Snake River Juvenile Salmon Migration Feasibility Study.

• Columbia River Channel Improvement Project.

The Corps has conducted a series of studies to evaluate appropriate in- water and upland disposal sites for dredged material and the effectiveness of habitat creation with dredged material deposited in water in shallow and mid-depth areas. In addition, the Corps reviewed and considered major projects and plans from throughout the study area, both within and outside of their jurisdiction.

Plan alternatives considered in combination with past and present dredging and disposal activities and other reasonably foreseeable plans and projects are not anticipated to cumulatively adversely affect the resources analyzed in the DMMP/EIS. The in-water disposal to create juvenile salmonid rearing habitat, when coupled with other measures being taken by the region to improve fish passage, may have a positive effect on juvenile salmonid survival.

RECOMMENDED PLAN/PREFERRED ALTERNATIVE

The Corps' preferred alternative, or Recommended Plan, for long-term management of dredging is "Alternative 4 - Maintenance Dredging With Beneficial Use of Dredged Material and a 3-Foot (0.9-m) Levee Raise." Alternative 4 most completely and efficiently meets the project purpose and need at the least cost, while presenting potential environmental impacts that are no greater, and often less, than other alternatives considered.

The recommended plan also represents the greatest beneficial use of dredged material that can be implemented on a programmatic basis at this time. Furthermore, the plan incorporates an adaptive management approach that provides for on- going evaluation of proposed dredging and dredged material management activities and opportunities to adapt and adjust actions based on these evaluations. Alternative 4 provides the most flexibility for identifying, evaluating, and potentially implementing beneficial uses of dredged material. The plan becomes the basis for cost sharing of other beneficial uses of dredged material that may be identified in the future as each separate dredging activity is planned and executed. Beneficial uses of dredged material may be adopted on a case-by-case basis under this plan as opportunities become available and, if necessary, when local sponsors agree to fulfill sponsorship requirements. To continue to optimize the use of dredged material, the Corps will coordinate potential beneficial uses for each dredging activity with the LSMG prior to the start of dredging. Figure ES-4 displays the decision tree that the Corps would use to determine the type of dredging and the disposal plan for each activity.

 

Figure ES-4. Disposal Site Selection Decision Tree

The 3-foot (0.9-m) levee raise feature is the preferred plan for maintaining the flow conveyance capacity in the Snake and Clearwater Rivers confluence area of Lower Granite reservoir because it meets the purpose and need and produces maximum net benefits in excess of costs. Raising the levee was found to reduce the need for dredging in the confluence area of Lower Granite reservoir and, therefore, is considered as a part of this DMMP. Selection of the levee raise as the preferred flow conveyance restoration method was based on the maximization of net benefits determined from a risk-based flood damage assessment and annual costs amortized over the remaining 74 years of the project life. Levee construction would not start until after 2005 and after any necessary appropriation and authorization is obtained.

Dredging projects implemented under this DMMP can be initiated in response to a variety of conditions described in the discussion of the Local Sediment Management Group above.

The Corps has identified the first dredging activity that would be conducted under the DMMP. This dredging is currently proposed for winter 2002-2003 and includes dredging the navigation channel at the confluence of the Snake and Clearwater rivers, several port facilities in the Lewiston-Clarkston area, several recreation facilities in Lower Granite and Little Goose reservoirs, navigation lock approaches to Lower Granite and Lower Monumental Dams, and several other potential areas. The Corps is currently proposing using dredged material to develop woody riparian habitat at the Chief Timothy Habitat Management Unit and/or using in-water disposal to create fish habitat in Lower Granite reservoir as the beneficial use of the dredged material. Appendix N provides a detailed description of the proposed dredging areas, the disposal plan, the sediment contaminant analysis, and the environmental impacts specific to this dredging activity.

This Dredged Material Management Plan/Environmental Impact Statement (DMMP/EIS) presents the U.S. Army Corps of Engineers' Walla Walla District (Corps') programmatic plan for:

• Maintenance of the authorized navigation channel in the lower Snake River reservoirs between Lewiston, Idaho, and the Columbia River, and McNary Lock and Dam (McNary) reservoir on the Columbia River for 20 years after the Record of Decision (ROD) is signed.

• Maintenance of limited public facilities within the reservoirs, such as recreational boat basins and irrigation intakes for the wildlife habitat management units (HMUs).

• Management of dredged material from these reservoirs.

• Maintenance of flow conveyance capacity at the most upstream extent of the Lower Granite Lock and Dam (Lower Granite) reservoir for the remaining economic life of the project (to year 2074).

This section presents background and introductory information on the formulation of this DMMP/EIS, including the purpose and need, authorities for this study, and the Corps' operation of the lower Snake River and McNary reservoirs, historic maintenance and dredging activities, and related activities.

1.1 Study Authority

The Corps' Dredged Material Management Study (DMMS) was initiated under the guidance provided in Engineer Circular (EC) 1165-2-200, Dredged Material Management Plans, which directs the development of DMMP's for Federal navigation projects, groups of inter-related harbor projects, and systems of inland waterway projects. It is Corps policy to dispose of dredged material associated with the construction or maintenance dredging of navigation projects in a manner that is the least costly, is consistent with sound engineering practice, and that meets Federal environmental standards. Guidance for developing DMMPs is now incorporated in Engineer Regulation (ER) 1105-2-100, Planning Guidance Notebook. The ER 1105-2-100 also provides the requirements, as well as principles and guidelines, for conducting planning studies within the Corps' Civil Works program and ensuring environmental compliance through the planning process. Section 3-2 of ER 1105-2-100 provides specific guidance on the maintenance of navigation projects and the preparation of dredged material management plans. A least-cost alternative, which is compliant with environmental laws, forms the "base plan" against which other plan alternatives can be compared. Through the DMMP planning process, the Corps has considered a range of management strategies, including approaches to reduce the need for dredging and to beneficially use dredged materials, and has incorporated these strategies into its alternatives development and evaluation process.

On May 4, 1995, the Corps Director of Civil Works provided guidance to the Commander, North Pacific Division, by memorandum entitled "Lower Granite Lock and Dam, Washington, Sedimentation Studies Related to the Level of Protection Provided to the City of Lewiston, Idaho." This memorandum discussed a study to evaluate restoring the performance of project levees constructed to protect Lewiston, Idaho, from inundation caused by the Lower Granite project. It states, "The study should evaluate a range of alternative risk management plans, including modifications in the operation of the project and increased dredging." In compliance with this memorandum, consideration of reestablishing the flow conveyance capacity at Lewiston, Idaho, is included in the DMMS.

1.2 PURPOSE AND NEED

The purpose of this DMMP/EIS is threefold:

1. To develop and evaluate alternative programs to maintain the authorized navigation channel and certain publicly owned facilities in the lower Snake River and McNary reservoirs for the next 20 years;

2. To develop and evaluate alternative measures to maintain the flow conveyance of the Lower Granite reservoir for the remaining economic life of the project (through 2074); and

3. To develop and evaluate alternative programs of managing dredged material removed from these five reservoirs in a cost-effective, environmentally acceptable, and, wherever possible, beneficial manner.

The Corps is authorized by Congress to maintain a navigation system on the lower Snake and Columbia Rivers and to manage the lock and dam/navigation projects (generally referred to as "projects" or "reservoirs" in this document) on the lower Snake River from Lewiston, Idaho, to the McNary project at Umatilla, Oregon, on the Columbia River (which includes the confluence of the Columbia and Snake Rivers). The Corps also maintains publicly owned recreational areas (such as marinas and swimming beaches), irrigation intake facilities for wildlife Habitat Management Units (HMUs) and recreation sites, and port access channels within the lower Snake River and McNary reservoirs. Historically, the Corps has dredged accumulated sediments from the navigation channel and the other facilities noted above on these reservoirs in order to maintain their operational capacities. Maintenance dredging actions are in response to a variety of conditions including, but not limited to: emergency situations which would result in an unacceptable hazard to navigation; programmed periodic dredge maintenance of known persistent shoal areas which impede navigation; and removal of sediment that presents a hydraulic flow impediment.

In addition, sediment accumulation in the upstream reach of Lower Granite reservoir at the confluence of the Clearwater and Snake Rivers has reduced the flow conveyance capacity of the river channel. If allowed to continue, this sedimentation would reduce the flow capacity to a point that the Standard Project Flood [(SPF) an estimated or hypothetical flood that might be expected from the most severe combination of weather and flow conditions that are considered reasonably characteristic of the geographical area] would be expected to overtop the levees in Lewiston, Idaho, long before the end of the economic life of the project is reached in 2074 (Corps, 1993). To date, dredging has been the method of choice for the removal of this sediment and restoration of the flow capacity.

The Corps policy stated in EC 1165-2-200 relates to development of a DMMP to address the dredged material management requirements of the navigation projects within its jurisdiction. This policy encourages the development of a range of feasible management alternatives that are cost effective and environmentally acceptable, and to seek to optimize beneficial uses of dredged materials that may be generated. In preparing the DMMP, the Corps will assess opportunities to minimize dredging requirements and maximize beneficial uses of dredged materials.

The Corps, Walla Walla District, is preparing this DMMP/EIS to address the maintenance of the authorized navigation channel and specific public facilities for 20 years after the ROD is signed. This DMMP/EIS presents and analyzes management alternatives and addresses management of dredged materials that are likely to result from these activities.

In addition, since dredging for flow capacity represents a significant quantity of historically dredged material volumes, this DMMP/EIS evaluates future maintenance of flow conveyance through the remaining economic life of Lower Granite. Various methods to maintain flow conveyance in Lower Granite are considered, including dredging and raising the existing levees in Lewiston as a means of reducing dredged material volumes.

The development of the DMMP/EIS is consistent with the requirements of EC 1165-2-200 and has been integrated with the requirements of the National Environmental Policy Act (NEPA).

1.3 DESCRIPTION OF THE STUDY AREA

Navigation on the Columbia and Snake Rivers has historically provided an important route of access into and from the interior Columbia and Snake River basins (plate 1). As a part of its Congressional mandate, the Corps continues to maintain, enhance, and operate the navigational improvements on the Columbia and Snake Rivers waterway. The Columbia and Snake Rivers projects include channels, locks, and dams providing access to the ports, moorage, and recreational areas along the rivers.

The Corps typically maintains authorized channels on an as-needed basis by dredging to maintain the authorized channel depth. Maintenance dredging of access channels to port and moorages occurs infrequently, on an as-needed basis. The Corps also periodically conducts maintenance dredging around public recreation areas, such as swimming beaches, boat basins, and irrigation intakes for wildlife HMUs and recreation sites managed by the Corps.

The Columbia and Snake Rivers navigation project begins at the mouth of the Columbia River near Astoria, Oregon, and extends to Lewiston, Idaho, on the Snake River, a distance of approximately 460 miles [740.3 kilometers (km)]. A 40-foot- [12.2-meter (m)-] deep, 600-foot-(182.9-m-) wide ship channel is authorized from the Columbia River Bar to Vancouver, Washington, and a 27-foot- (8.2-m-) deep, 300-foot- (91.4-m-) wide ship channel is authorized from Vancouver to The Dalles Lock and Dam (The Dalles) on the Columbia River. The 27-foot- (8.2-m-) deep channel is typically only maintained to a 17-foot (5.2-m) depth, reflecting the needs of vessels using this reach. A 14-foot- (4.3-m-) deep, 250-foot- (76.2-m-) wide channel is maintained from The Dalles through McNary on the Columbia River and through the four lower Snake River projects to Lewiston, Idaho.

Sill depths at the navigation locks limit the passage of vessels, commercial or recreational, on the Columbia and Snake Rivers. At most of the projects, upstream sills are 15 feet (4.6 m) below the Minimum Operational Pool (MOP). The MOP provides the clearance needed for a barge drafting between 13 and 14 feet (4 and 4.3 m), the typical draft of loaded barges operating in the Columbia and Snake River fleet.

This document covers five locks and dams for the upper portion of the Columbia and Snake Rivers navigation project: McNary, Ice Harbor Lock and Dam (Ice Harbor), Lower Monumental Lock and Dam (Lower Monumental), Little Goose Lock and Dam (Little Goose), and Lower Granite. Each of these projects is authorized to provide navigation facilities including locks with dimensions of 86 feet (26.2 m) in width and over 665 feet (202.7 m) in length to allow passage of a tug with a four-barge tow commonly used in river navigation. McNary lock provides a lift of approximately 75 feet (22.9 m), while each of the four Snake River locks and dams provide between 98- and 100-foot (29.9- and 30.5-m) lifts, raising navigation from elevation 265 feet mean sea level (msl) below McNary to elevation 738 feet msl in the Lower Granite reservoir. This portion of the waterway extends approximately 179 miles (288.1 km) from McNary to Lewiston, Idaho. The initial McNary project, including construction of the locks, was completed in 1954 and provided slackwater navigation to the Tri-Cities, Washington, area.

Ice Harbor, which began operation in December 1961, is approximately 8 miles (12.9 km) east of Pasco, Washington, and was the first dam constructed on the Snake River in Washington. Three more dams were built on the Snake River in Washington over the next 13 years: Lower Monumental (1969), Little Goose (1970), and Lower Granite (1975). Construction of these dams has created a series of slackwater reservoirs on the Snake River, adding an additional 140 miles (225.3 km) to the Columbia and Snake Rivers shallow draft inland navigation system. This navigation system has resulted in a significant shift in the economy of eastern Washington as new inland ports have become established to handle the needs of barge shippers. Wheat, barley, wood chips, and other wood products are the primary commerce downbound from this region, with petroleum and fertilizer the principal commerce upbound. These shipments depend on the availability of a navigation system that provides a 14-foot (4.3 m) draft channel for barge tows.

1.4 EXISTING FEDERAL PROJECT AUTHORITY

The portion of the Columbia and Snake Rivers navigation system addressed in this DMMP/EIS was authorized by Section 2 of the River and Harbor Act of 1945 (Public Law 79-14, 79th Congress, 1st Session) and approved March 2, 1945, in accordance with House Document 704, 75th Congress, 3rd Session. The projects include:

• McNary Lock and Dam - Lake Wallula, Columbia and Snake Rivers, Oregon and Washington.

• Ice Harbor Lock and Dam - Lake Sacajawea, Snake River, Washington.

• Lower Monumental Lock and Dam - Lake Herbert G. West, Snake River, Washington.

• Little Goose Lock and Dam - Lake Bryan, Snake River, Washington.

• Lower Granite Lock and Dam - Lower Granite Lake, Snake River, Washington.

Each of these projects is authorized to provide for slackwater navigation, irrigation, hydroelectric power generation, recreation, and fish and wildlife.

Public Law 87-874, Title II - Flood Control Act of 1962, October 23, 1962, states:

The projects and plans for the Columbia River Basin, including the Willamette River Basin, authorized by the Flood Control Act of June 28, 1938, and subsequent Acts of Congress, including the Flood Control Acts of May 17, 1950, September 3, 1954, July 3, 1958, and July 14, 1960, are hereby modified to include the projects listed below for flood control and other purposes in the Columbia River Basin (including the Willamette River Basin) substantially in accordance with the recommendations of the Chief of Engineers in House Document Numbered 403, Eighty-seventh Congress: Provided, That the depth and width of the authorized channel in the Columbia-Snake River barge navigation project shall be established as fourteen feet and two hundred and fifty feet, respectively, at minimum regulated flow."

Public Law 102-580, Water Resources Development Act of 1992, Section 109, authorizes the Secretary of the Army to maintain navigation access to, and berthing areas at, all currently operating public and private commercial dock facilities associated with or having access to the Federal navigation project on the Columbia, Snake, and Clearwater Rivers from Bonneville Lock and Dam (Bonneville) to, and including, Lewiston, Idaho, at a depth commensurate with the Federal navigation project. A one-time appropriation, to carry out the provisions of this section, was made in fiscal year 1992. Future Federal maintenance of non-Federal commercial channels authorized under this Act would require special appropriation legislation. The Corps is also authorized to maintain associated publicly owned recreation areas and wildlife HMUs.

Lower Granite includes levees as appurtenant facilities of the authorized project to allow normal operating water surface elevations of 733 to 738 feet msl in the Lewiston, Idaho, and Clarkston, Washington, areas. These backwater levees constructed around Lewiston were designed to protect the city from inundation during the occurrence of the SPF and to maintain flow conveyance capacity.

1.5 HISTORY AND BACKGROUND

Several locations along the Snake and Columbia Rivers have required periodic dredging to maintain the authorized channel depth, and several ports have experienced frequent sediment-related problems in accessing their loading or docking facilities. In the 8-year period from 1991 through 1998, there were navigation-related dredging activities in all of the reservoirs in the study reach. Some of these dredging projects were directed toward cleaning out berthing areas, turning basins, and access channels for individual ports, and some were directed toward restoring the authorized depth in the main navigation channel. The Corps has also performed periodic maintenance dredging of relatively small amounts of sediments around public recreation areas and irrigation intakes for wildlife management areas. Table 1-1 presents the history of dredging of this system.

Several major tributaries enter the Snake or Columbia Rivers within the study area, and most are heavy sediment contributors in high runoff years. Projections of sediment inflow and deposition indicate more sediment buildup at the tributary mouths that may, over time, affect the navigation channel, requiring more frequent dredging at these locations.

Lower Granite, the most upstream of the four lower Snake River dams, is the final link in the inland waterway system that provides slackwater navigation to the cities of Lewiston, Idaho, and Clarkston, Washington. Because this reservoir is the most upstream in the lower Snake River system, it is the predominant sediment collection area for a large sediment-contributing drainage area that includes the Salmon, Grande Ronde, and Imnaha Rivers; the main stem of the Clearwater River; and the local drainage of the Snake River between the Hells Canyon complex and Lower Granite. The upper reach of the Lower Granite reservoir serves as a sediment trap for most of the material carried in suspension in the free-flowing reaches of the contributing rivers. The quantity of sediment that collects in the Lower Granite reservoir exceeds the quantities observed in each of the other lower Snake River reservoirs and in the McNary reservoir.

The deposition of sediments at the upstream end of the Lower Granite reservoir impacts backwater levee systems constructed at the cities of Lewiston and Clarkston. The Lower Granite project included a backwater levee system in lieu of relocating the business district of Lewiston. This levee system was not designed primarily to provide flood control to Lewiston; rather, it was designed and constructed to be an upstream extension of the dam. This project element was designed to allow the Lower Granite reservoir to pass an SPF event while protecting Lewiston from inundation.

The levee system was designed to provide a minimum freeboard of 5 feet (1.5 m) during the SPF event of 420,000 cubic feet per second (cfs) [11 893.1 cubic meters per second (m³/s)] on the Snake River below the confluence of the Clearwater River. Since the reservoir was filled in 1975, sediment deposition has reduced the channel capacity, causing the computed water surface elevations associated with a particular discharge to rise. The sedimentation deposition has restricted the channel so that the SPF event cannot pass without seriously encroaching into the levee freeboard. Subsequent studies conducted by the Corps indicate that overtopping of the levees could occur in the future.

Sediment accumulation in Lower Granite reservoir continues to reduce the level of protection provided by the levees. Less than 3 feet (0.9 m) of the originally designed 5 feet (1.5 m) of levee freeboard remain for the SPF. Approximately 2.2 million tons (2.0 metric tons) or 3.2 million cy (2.4 million m³) of sediment collects in the reservoir annually. During the first 12 years of operation, the average annual reduction in levee freeboard was 3 inches [7.6 centimeters (cm)] per year. Projections indicate that, without corrective action, the SPF could overtop the existing levees.

A dredging and experimental in-water disposal test program was conducted over the period between 1985 and 1993 to determine acceptable solutions to the sedimentation problems in Lower Granite reservoir. Disposal of dredged material was a problem due to limited availability of upland disposal sites combined with the need to dredge for navigation and flow conveyance. Dredged material from the upper reservoir was considered to be potentially beneficial in creating shallow water habitat. Shallow water habitat provides foraging opportunities and short-term rearing for downstream migrating salmonid fishes and spawning and rearing habitat for resident game fishes. This experimental in-water disposal test was implemented in 1985 with an exhaustive monitoring program to assess the value of using dredged material for fish habitat enhancement. As a part of this test, an underwater bench and island (Centennial Island) were constructed at mid-depth (20 to 60 feet) (6.1 to 18.3 m) with additional disposal at a deep-water (greater than 60 feet) (greater than 18.3 m) site between river mile (RM) 120 and Lower Granite. Fish assemblages were sampled before the test began in 1985 and after construction of the dredged disposal island in 1993 to assess local changes in community structure. The results of this test suggest that construction of shallow water habitat using dredged material has a potential for increasing habitat complexity in Lower Granite reservoir.

1.6 RELATED ACTION PROGRAMS

In February 2002, the Corps issued the Final Environmental Impact Statement (FEIS) for the Lower Snake River Juvenile Salmon Migration Feasibility Study (Feasibility Study), which analyzed measures that may increase the survival of juvenile anadromous fish through the lower Snake River project [which includes the four lowermost dams operated by the Corps on the Snake River (Ice Harbor, Lower Monumental, Little Goose, and Lower Granite)] and assist in the recovery of listed salmon and steelhead stocks. Several key aspects of the Feasibility Study and this DMMP/EIS are interrelated. The history of the development of the Feasibility Study and its relationship to this DMMP/EIS are discussed below. The Final Feasibility Study EIS and supporting documentation are incorporated by reference in the DMMP process.

On November 20, 1991, the National Marine Fisheries Service (NMFS) declared the Snake River sockeye salmon as Endangered effective December 20, 1991 (56 FR 58619). Snake River spring/summer chinook and Snake River fall chinook salmon were listed as Threatened on April 22, 1992 (57 FR 14653). Critical habitat was designated for Snake River sockeye, spring/summer chinook, and fall chinook salmon on December 28, 1993 (58 FR 68543). Snake River basin steelhead were formally listed as Threatened on August 18, 1997 (62 FR 43937).

On March 2, 1995, NMFS issued a Biological Opinion for the Reinitiation of Consultation on 1994-1998 Operation of the Federal Columbia River Power System and Juvenile Transportation Program in 1995 and Future Years. The 1995 Biological Opinion established measures necessary for the survival and recovery of Snake River salmon listed under the Endangered Species Act (ESA).

The Corps' primary responsibility in implementing the measures prescribed in the 1995 Biological Opinion is to study those measures that are associated with dams and reservoirs and that influence fish migration through the hydro system. Thus, the purpose of the Feasibility Study is to evaluate and screen alternative measures that may increase the survival of juvenile anadromous fish through the lower Snake River project and, therefore, assist in the recovery of listed salmon and steelhead stocks.

The Feasibility Study considered four alternatives; three of the alternatives would keep the dams in place, while one alternative includes breaching of the earthen portion of the four dams. Breaching the dams would allow the lower Snake River to return to a more free-flowing condition, while eliminating hydropower production and the ability to use river navigation for the shipments of goods between the Lewiston-Clarkston area and the Tri-Cities area. The Corps considered public input on the Feasibility Study received through extensive outreach and public comments on the Draft FR/EIS. The recommended plan documented in the Feasibility Study Final EIS is "major system improvements (adaptive migration)," and features structural and operational measures that are considered to be technically feasible, and which the Corps has the capability to design, construct, and operate.

The Feasibility Study process and its ultimate recommendations may affect the management of the lower Snake River and McNary reservoirs. This DMMP/EIS addresses long-term (20 years) management of dredged material by providing a programmatic "framework" or "road map." As such, this DMMP/EIS incorporates a number of assumptions about the future operations of the lower Snake River projects, including the assumption of continued navigation on the lower Snake River (i.e., that the four lower Snake River dams would not be breached). However, by incorporating this assumption, the DMMP/EIS does not pre-determine the outcome of the Feasibility Study process, nor whether the lower Snake River dams would be kept in place or breached. In fact, the DMMP is based upon an adaptive management approach that would allow the Corps a degree of flexibility to accommodate certain regulatory, policy, or environmental changes over the 20-year timeframe of the plan.

As a programmatic plan, this DMMP/EIS accounts for the fact that the Feasibility Study process may determine that the lower Snake River dams are to stay in place, be modified in place, or breached. If the dams stay in place, this DMMP/EIS would continue to set the management objectives for the lower Snake River and McNary reservoirs. On the other hand, if the Feasibility Study process concludes that the dams should be modified or removed, this DMMP/EIS would be necessary for the interim management of the lower Snake River projects. Also, if the lower Snake River dams are breached, this DMMP/EIS would need to be revised to address the changed navigation and sedimentation conditions in McNary reservoir. On the other hand, data from the NMFS 2000 BiOp check-in points in 2003, 2005, and 2008 and other new information could result in a decision to modify or breach these four dams, this DMMP would still be necessary for interim management and to address conditions in the McNary Reservoir.

After publication of the Draft FR/EIS, NMFS issued a Biological Opinion (December 21, 2000) to the Bonneville Power Administration (BPA), the Corps, and the Bureau of Reclamation. In this Biological Opinion, NMFS calls for various Habitat Actions. One of the stated goals of these Habitat Actions as they apply to main stem habitat is to "improve main stem habitat on an experimental basis and evaluate the results." The specific Action Item, Action #155, states that, "BPA, working with the BOR, Corps, the Environmental Protection Agency (EPA), and the U.S. Geological Survey, shall develop a program to: (1) identify mainstem habitat sampling reaches, survey conditions, describe cause-and-effect relationships, and identify research needs; (2) develop improvement plans for all mainstem reaches; and (3) initiate improvements in three mainstem reaches. Results shall be reported annually." As one means of achieving this, the Biological Opinion states that, "BPA, working with the Corps, will take immediate steps to begin to address these uncertainties by . . . improving mainstem reaches in ways that mimic the range and diversity of the historic habitat conditions as much as possible, and monitoring and evaluating the results." The beneficial use of dredged materials, including development of mid-depth and shallow water rearing habitat as proposed in this DMMP/EIS would contribute toward these actions proposed by NMFS.

Whatever the outcome of the Feasibility Study process, this DMMP/EIS would provide management guidance over the short term. The adaptive management approach of the DMMP's recommended plan would also allow it to be modified or amended to account for changes that may occur to the system over the next 20 years.

1.7 ECONOMIC JUSTIFICATION

The recommended DMMP is economically justified by confirming that transportation savings over the next 20 years resulting from the dredging program exceed the cost of maintenance of the navigation project. Benefits in transportation costs to barge shippers of commodities on the lower Snake River system were compared with the cost of providing the authorized channel depths and maintaining the navigation features of the system.

Justification for the restoration of flow conveyance capacity in the Lower Granite reservoir is determined by comparing costs of alternatives to increase conveyance with the expected reduction in flood damages based on the results of a risk-based flood damage assessment. Economic feasibility of an acceptable alternative to restore flow conveyance capacity is based on maximization of net benefits computed over the remaining economic life of the project to year 2074 at a 6.875 percent interest rate.

1.7.1 Navigation

Barge navigation on the lower Snake River system accommodates the downbound transport of wheat, barley, wood chips, other wood products, and miscellaneous agricultural products and the upbound transport of petroleum, fertilizer, and other consumer goods. The authorized navigation project on the lower Snake River provides 14 feet (4.3 m) of depth at normal operating pool levels. Impacts to shallow draft commercial navigation from sedimentation and shallowing of the authorized channels above McNary are estimated from information presented in the Columbia River System Operation Review, Final Environmental Impact Statement, dated November 1995, Appendix O, Economic and Social Impact, page 453. Transportation costs for commerce moving to and from the Snake River projects on the Columbia and Snake Rivers system were estimated at $414.43 million in 1992 under present authorized channel depths. The cost of transporting the same commerce over alternative landforms of transportation was estimated to be $458.33 million. The difference of $43.90 million (that is, $458.33 minus $414.43) can be considered the annual benefits attributable to barge navigation on the Snake River system. A similar evaluation was presented in the February 2002 FR/EIS. The FR/EIS estimated the increased average annual transportation costs resulting from the elimination of barge transportation at $43.191 million in 2002 dollars [Snake River Juvenile Salmon Migration Feasibility Report/EIS, appendix I, February 2002, Table ES-15]. Wheat and barley shipments represented more than 60 percent of the tonnage and more than 90 percent of the transportation savings. Barge commerce above McNary is expected to continue to grow over the next 20 years and transportation benefits are expected to grow similarly. Forecasts of barge transportation in the 20-year period of this DMMP/EIS show tonnage to increase to between 7.9 and 10 million tons (7.1 and 9.0 metric tons) by the year 2020 from nearly 7 million tons (6.3 metric tons) in the mid-1990's.

Average annual costs to provide the dredging maintenance of channels and operate the navigation features in the five dams and reservoirs were estimated and compared with estimates of transportation savings described above to determine the economic justification of continued maintenance of the system. Channel maintenance average annual costs are estimated at $560,000 computed over the 20-year period at a 6.875 percent interest rate. This cost estimate is based on maintaining the authorized navigation channel dimensions over the next 20 years using clamshell dredging, bottom-dump barges, and in-water disposal of the dredged material. Use of hydraulic equipment was not considered acceptable because of the anticipated adverse impact on endangered fish resources. Disposal at upland sites instead of in-water sites was considered, but found to be more costly and provide less environmental benefit than in-water disposal. In addition to channel maintenance costs, annual costs include $2.14 million (expended in fiscal year 1998) for the operation and maintenance of navigation locks at each of the five reservoir projects. Comparing the annual $43.191 million in transport savings estimated for just the Snake River portion with the combined channel average annual maintenance and 1998 navigation lock operation and maintenance costs of $2.70 million ($0.56 + $2.14) results in a benefit-to-cost ratio of 16.0 to 1.0. This portion of the Columbia and Snake River navigation system provides a very strong economic justification for the continued maintenance of this system. The study described in section 1.6 considers various levels of navigation clearances and evaluates the resultant effects. All alternatives described in this DMMP/EIS provide 14-foot (4.3-m) navigation clearances over the Federal navigation system. Appendix A, Hydrologic Analysis, contains a summary description of the dredging operations and appendix B, Cost Estimates, presents the cost estimate of each dredging and disposal alternative.

Consideration can also be given to reduced maintenance that would result in a change in depth to the authorized Federal channel causing transportation companies to light load their equipment to accommodate a shallower channel. Navigation benefits and dredging costs can be compared on an incremental basis for different channel conditions to determine if channel maintenance is more cost effective than light-loading barges. Commodity transportation and barge cost data prepared for the Lower Snake River Feasibility Study were used to determine the feasibility of the maintenance dredging proposed and evaluated in the DMMP/EIS. For this analysis two shallower Federal navigation channels, with controlling depths of 13 feet and 12 feet, were assumed to result from termination of maintenance dredging. Grain shipments, representing 78.8% of the commerce on the Snake River for the period of 1987 to 1996, were selected to represent the impacted commerce. Grain barge costs for shipments from the various ports on the Snake River system were developed to reflect light-loading to accommodate the shallower channels. Reduced cargo capacity of the standard 3,600-ton grain barge (274 feet long, 42 feet wide, and 13.5 feet draft) with drafts of 12.5 feet and 11.5 feet were determined to be 3,270 tons and 2,950 tons, respectively. The impact of this reduced capacity would be to raise per ton barge costs by 10% and 22%, respectively. The resultant increase in transportation costs for moving the forecast grain shipments from the Snake River in the 20-year period was compared to the avoided annual cost of maintenance dredging. The result of this analysis, based on 1999 costs, indicated that dredging costs were equal to the estimated increase in barge costs when the channel capacity was reduced by only one foot. However, where channel depths were reduced by two feet, the cost of dredging was about half of the increased cost to barge transportation. In essence, shoaling that reduces the channel depth by one foot represents the "break even" point where maintenance dredging is feasible and cost effective when only grain shipments are considered. While this study was not an exhaustive analysis of the feasibility of reduced channel maintenance dredging, it indicates that dredging was more cost effective than light loading the present barge equipment. If all the waterborne commerce on the Snake River is considered the maintenance dredging of the channel would be clearly more feasible and cost affective than light loading barges.

1.7.2 Conveyance Capacity

Existing levees, protecting the city of Lewiston, Idaho, from reservoir backwaters, were built as a part of the construction of Lower Granite. Sediment deposition in the Lower Granite reservoir threatens to reduce the channel capacity and cause flows to overtop levees and flood developed areas. Correction of this condition has been the subject of memoranda between the Walla Walla District and Corps Headquarters. In a memorandum dated May 4, 1995, the Director of Civil Works, Corps of Engineers, stated that a study was needed to evaluate restoring the performance of the project levees constructed to protect Lewiston, Idaho. It further stated, "The study should evaluate a range of alternative risk management plans, including modifications in operation of the project and increased dredging." Flow conveyance could be provided by dredging and, therefore, it was considered appropriate to formulate the plan as part of this DMMP/EIS. This DMMP/EIS includes the results of the risked-based analysis conducted to determine the appropriate means of restoring the flow conveyance capacity in the confluence area of Lower Granite reservoir.

Risk-based analysis is an approach to evaluation and decision making that explicitly incorporates considerations of risk and uncertainty. This approach combines the underlying risk and uncertainty information so that the engineering and economic performance of a project can be expressed in terms of probability distributions. The objective is to identify and recommend a flood damage reduction alternative that reasonably maximizes expected net benefits (expected annual damages reduced minus the average annual cost of the alternative). No longer is protection against the SPF with 5 feet (1.5 m) of freeboard the criteria for the levees protecting the Lewiston-Clarkston area. As of 1977, the base year for the analysis, the project provided protection against a flow condition having a recurrence interval of 500 years. Sedimentation in the confluence area would reduce the protection by the year 2021 to a 167-year recurrence interval and by 2074 to a 83 year recurrence interval without any upgrade to the levee system.

A number of measures were considered to restore the flow conveyance capacity including making operational changes, dredging additional material to provide adequate channel capacity below elevation 738 feet msl, and raising the height of the existing levees to allow for water surface increases. Operational changes were found not to be an effective method of restoring flow conveyance capacity, as discussed in section 2, and this study concentrated on dredging and levee raise alternatives. All flow restoration options were considered to provide the flow conveyance needed after the navigation maintenance dredging program (considered the baseline in this study) had been implemented. Various dredging options including removing 300,000 cy (229 366.5 m³) per year, 1 million cy (764 555 m³) per year, and 2 million cy (1 529 110 m³) per year were considered. Levee modifications providing nominal raises of 3 feet (0.9 m), 4 feet (1.2 m), 8 feet (2.4 m), and 12 feet (3.7 m) were also considered. These levee raise alternatives are identified nominally by their largest levee height increase expressed to the nearest foot (meter). This identification is nominal since the actual levee raise varies along the length of the existing levee. Where necessary to protect against design water surface profiles for nominal levee raises exceeding 3 feet (0.9 m), the levee footprint was extended upstream as described in appendix E, Lewiston Levee Modification Extension Analysis. Cost estimates were developed for each of the dredging and levee raise alternatives and converted to annual costs based on 6.875 percent interest over the remaining life of the project to year 2074. Only those dredging costs above the base navigation maintenance plan were accepted as costs relating to flow conveyance capacity. Flood damage reduction estimates were obtained using the Corps Hydrologic Engineering Center Flood Damage Assessment (HEC-FDA) model. This model is consistent with the Corps' Engineering Manual 1110-2-1619, Risk-Based Analysis for Flood Damage Reduction Studies. Results from the risk-based model were converted to average annual damages reduced for each alternative and compared to their annual cost.

The risk-based flood damage assessment and economic analysis, presented in appendix C, Economic Analysis, indicates that a nominal levee raise of 3 feet (0.9 m) provides maximum net flood damage reduction benefits. Information presented on page 48 of appendix C was converted to average annual costs and benefits. This economic analysis shows that a nominal 3-foot (0.9-m) levee raise would have annual costs of $152,000 and annual flood damage reduction benefits of $689,000 with a net benefit of $537,000. A levee alternative providing a nominal 4-foot (1.2-m) raise would have average annual costs of $938,000 and annual flood damage reduction benefits of $793,000, producing net benefits of -$145,000. A dredging alternative providing somewhat higher flood damage reduction benefits to the 3-foot (0.9 m) levee raise would have annual costs of $1,233,000, approximately eight times greater than the levee alternative. The value of average annual flood damages that could occur without a modification was computed to be $941,000 over the life of the project discounted by 6.875 percent. None of the flow conveyance alternatives with annual costs that exceeded $941,000 could be considered economically feasible and, therefore, were not considered further. Accordingly, dredging alternatives to provide flow conveyance with average annual costs ranging from $1,233,000 to $4,706,000 are not considered feasible. Table 1-2 presents the results of these economic investigations. Appendix C and the remainder of this DMMP/EIS provide the details of the economic studies, with the incremental analysis results and discussion of impacts and mitigation requirements.

1.8 LOCAL SEDIMENT MANAGEMENT GROUP

A Local Sediment Management Group (LSMG) has been formed, and has met on three occasions (July 2000, February 2001, and December 2001), to provide input in the development of this DMMP/EIS, as well as coordination of the plan's implementation (i.e., the dredging and dredged material management activities). This group has been formed consistent with the inter-agency National Dredging Team's guidance (EPA, 1998a). Roles within the LSMG will continue to develop in accordance with policies and procedures currently evolving for the RDT, as referenced in the April 26, 2002 policy letter jointly signed by Brigadier General David A. Fastabend (Corps of Engineers Northwest Division Commander) and L. John Iani (EPA Region 10 Administrator).

The LSMG would assist in the development and adoption of appropriate method(s) for management of dredging and use and/or disposal of dredged material from Federal navigation and maintenance projects and dredging activities regulated under Section 404 of the Clean Water Act. In the formulation of these management policies, the LSMG would be asked to consider key environmental laws and regulations involved in this process; consider the responsibilities of other Federal, state, and local resource agencies; and help develop a coordination process for dredging and beneficial use of dredged material. In addition the LSMG would assist the Corps in evaluating dredging and dredged material management activities and options consistent with an adaptive management approach.

The general objectives of the LSMG are:

• Provide an interagency approach to dredged material management.

• Promote consistency in dredging and sediment management activities.

• Assist in development of monitoring plans and sediment sampling and testing framework.

• Facilitate adaptive management and beneficial use of dredged materials.

• Promote consideration of all environmental laws and regulations.

• Consider necessary cultural resource protection.

• Discuss and evaluate possible strategies to reduce sediments entering the lower Snake River system.

• Involve other stakeholder groups and pursue consistency with their plans.

The Corps anticipates that the LSMG will convene regularly, either annually or semi-annually, depending on the Corps' anticipated dredged material management activities. The LSMG will consider all dredging and dredged material management activities for the ensuing time period. Specifically, it is envisioned that the LSMG will consider proposed dredging, suggest ways of potentially reducing dredging requirements, explore promising beneficial uses of dredged materials, and comment on proposals for in-water habitat creation using dredged materials.

As situations develop which call for maintenance dredging, the LSMG would be informed. The situations expected to require maintenance dredging could include, but would not be limited to:

• Emergencies involving shoaled areas that pose a serious risk to navigation of commercial vessels as indicated by records of groundings, complaints by shippers, and/or condition surveys of the navigation channel.

• Programmed/periodic dredge maintenance activities based on well-established historical records of persistent shoaling in a navigation channel that could pose a serious risk to navigation of commercial vessels.

• Shoaled areas that pose a serious risk to navigation and moorage of recreational craft as indicated by comments of operators of recreational boat facilities and/or condition surveys.

• Sedimentation to irrigation intakes associated with Lower Snake River Habitat Management Units (HMU) which restricts the ability to deliver irrigation water to the HMU.

• Sedimentation to irrigation intakes associated with Corps-managed recreation areas.

• Advanced maintenance of a commercial navigation channel or berth which historically requires dredging to remove shoals that pose a serious risk to navigation, when an opportunity to meet a specific environmental restoration need for beach nourishment exists and/or when the dredging can be combined with other maintenance dredging to lower the cost and minimize the dredge related disturbance to transportation and local business activities.

Further, it is anticipated that the LSMG would provide a forum to address historic inconsistencies in dredging and disposal methods and in-water work windows, and discuss ways of bringing consistency to dredging-related activities within the study area. The LSMG would also serve as a forum for providing suggestions to the Corps on improving the implementation of the DMMP/EIS.

The following Federal and state agencies and tribes with responsibilities applicable to the DMMP/EIS have been asked to participate in the LSMG to facilitate the accomplishment of the general objectives:

Additionally, public ports within the study area have been invited to participate in the LSMG. Other local entities with an interest in management of the resources involved in dredging and disposal activities (e.g., counties, municipalities, environmental groups, and transportation and industrial interests) would be asked to participate on a regular basis.

The LSMG has been identified as a forum for discussion of possible measures to reduce sedimentation in the lower Snake River system and McNary reservoir. To facilitate these discussions, land management and conservation agencies such as the U.S. Forest Service, the Natural Resources Conservation Service, and others that may have a role in sediment reduction strategies, will be asked to participate in the LSMG.

1.9 LOCAL SPONSORS

Beneficial uses of the dredged material may be undertaken solely by the Corps, without non-Federal cost sharing, where it is consistent with the authorized project purpose (such as woody riparian habitat or shallow water habitat development). The Corps' project authorization requires maintenance of the navigation channel in the lower Snake River and in the Columbia River upstream of McNary. Historically, the ports and other users located on the rivers that benefit from and rely on maintenance of navigation on this inland waterway system have requested that the Corps provide dredging to maintain their facilities. The dredging of ports and other non-Federal facilities is a reimbursable cost paid to the Federal Government.

Potential local sponsors for navigation maintenance activities on the lower Snake River and McNary reservoirs include the public port authorities listed on the following page. In addition, there are numerous private port and dock facilities on the lower Snake and Columbia Rivers within the study area. Periodic dredging of port facilities may be required. For example, in the 1997-1998 confluence dredging, the Corps dredging contractor removed 3,687 cy (2 818.9 m³) of material from the Port of Lewiston and 12,154 cy (9 292.4 m³) from the Port of Clarkston.

Other potential local sponsors of dredged material management activities include agencies or individuals who are willing to share in the cost of beneficial use of dredged material. Beneficial uses of dredged material to protect, create, or restore aquatic and wildlife habitat are authorized under Section 204 of the Water Resources Development Act of 1992. Implementation of beneficial use projects is conditioned on local sponsors agreeing to pay 25 percent of the cost of implementing the project and 100 percent of maintenance costs. Similarly, use of dredged material for other purposes not related to ecological restoration (e.g., use as fill or cover material) may be undertaken provided additional costs to Federal agencies are not incurred. Local sponsors who identify such a beneficial use are responsible for financing all the costs associated with implementing and maintaining the use. The LSMG would serve as a forum for identifying sponsors and planning beneficial uses of dredged materials.

Potential local sponsors for beneficial use of dredged material include:

• Port of Whitman County to fill additional dredged material disposal cells at Port of Wilma.

• Port of Whitman County as a raw material source for production of potting soil.

• State wildlife agencies and wildlife organizations for habitat creation by shoreline terracing and covering exposed riprap.

• The U.S. Department of Energy for capping contaminated material in environmental restoration projects at the Hanford Reservation.

• Public landowners.

Potential beneficial uses of dredged material are discussed in detail in section 2.5.4.

The Corps' planning guidelines and NEPA require the consideration and analysis of a broad range of alternative approaches in the development of this DMMP/EIS. Section 2 presents the process to formulate the plan alternatives that were considered by the Corps in developing this DMMP/EIS (figure 2-1). This process includes:

• The development of plan measures (or types of actions) that, of themselves, address one or more of the requirements of the purpose and need discussed in section 1.2.

• Screening the plan measures to determine their effectiveness and suitability to include in plan alternatives.

• Formulating plan alternatives (or packages of one or more plan measures) that fully address the requirements of section 1.2, Purpose and Need.

• Those alternatives that reasonably and efficiently meet the Corps' planning objectives are further evaluated and compared in detail in sections 3 and 4. From these alternatives, a preferred alternative (or "recommended plan") would be selected. In addition, the "No Action (No Change)" alternative is presented and evaluated.

 

Figure 2-1. DMMP/EIS Plan Formulation Process

2.1 INITIAL OPTIONS

The Corps' DMMS examined methods for maintaining the existing 14-foot (4.3-m) draft navigation channel and other related features in the five reservoirs on the Columbia and lower Snake Rivers:

• Lake Wallula (McNary).

• Lake Sacajawea (Ice Harbor).

• Lake Herbert G. West (Lower Monumental).

• Lake Bryan (Little Goose).

• Lower Granite Lake (Lower Granite).

This DMMP and programmatic EIS are built on studies that have been ongoing since the mid-1980s and address management of dredged material for the next 20 years.

In addition to addressing the navigation maintenance needs, this study examines methods to maintain flow conveyance capacity in the upper reach of Lower Granite reservoir through the remainder of its economic life to year 2074 (Corps, 1993). Flow conveyance capacity is achieved currently through dredging. The continued need for flow conveyance capacity maintenance was based on the results of a risk-based flood damage assessment that considered the conditions with the 14-foot (4.3-m) navigation channel maintained. Dredging alternatives that both maintain navigation and meet the feasible flow conveyance needs were developed and compared to a full array of alternatives including levee raise alternatives. Levee raise alternatives were found to be a cost-effective substitute for dredging to achieve flow conveyance. The objective was to select an alternative that maximized flow conveyance capacity and net flood damage reduction benefits, based on engineering, environme ntal, and social criteria, and present it in this DMMP/EIS.

In accordance with the requirements of the NEPA, a broad range of alternatives that could potentially meet the stated purpose and need was developed. The Corps conducted public scoping meetings, consulted with state and Federal environmental and resource agencies, and conducted technical studies to develop a range of conceptual alternatives that addressed the plan's purpose and need. Alternatives were developed from a combination of possible measures, as described in section 2.2. See Sec. 6.1 for further discussion in scoping process. The process and criteria for screening the alternatives to determine whether they were environmentally, economically, technically, and administratively feasible are described in section 2.3. The measures removed from further consideration are discussed in section 2.4. Finally, sections 2.5, 2.6, and 2.7 present the alternatives that are evaluated in the EIS, mitigation, and the Corps' recommended plan, respective ly. The Corps also considered public comments submitted in response to the Draft DMMP/EIS.

2.2 MEASURES CONSIDERED

Various measures or types of actions that addressed the program purposes were developed; often measures were combined. Initially, non-structural measures were considered to meet the needs of maintenance of the navigation channel and related facilities in all five reservoirs and to maintain the flow conveyance capacity of Lower Granite reservoir. These measures include land use changes that would restrict the inflow of sediment and the possible use of in-water systems for control of sediment (such as bubble curtains). Reservoir drawdown, a non-structural measure for providing flow conveyance, was also considered. Next, the traditional method of dredging to meet the maintenance requirements and maintain the flow conveyance capacity of Lower Granite was considered. Finally, construction of a sediment trap and levee modifications were considered. These plan measures are listed in table 2-1 with an indication (noted by 4) of the program purposes that each address.

To provide a baseline for consideration of the alternatives, and in accordance with the requirements of NEPA, a "No Action (No Change)" alternative was considered. For the purposes of the DMMP/EIS, this alternative was a continuation of maintenance of the authorized navigation channel as directed by Congress in PL 87-874 (see section 1.4) and related maintenance features in the five reservoirs.

These categories of methods are summarized in sections 2.2.1 through 2.2.6. Alternatives were developed and screened to evaluate their feasibility, to determine which alternatives should be evaluated in the DMMP/EIS, and to select a preferred alternative, if appropriate.

Characteristics of the dredging options are summarized beginning in section 2.2.4, followed by a discussion of the upland disposal, beneficial uses, upstream sediment control structures, and levee modification measures. Summary descriptions of dredging operations are included in appendix A, Hydrologic Analysis, and cost information for each measure is presented in appendix B, Cost Estimates.

2.2.1 Change Upstream Land Uses and Land Management Practices to Control Sediment

Navigation channel and flow conveyance capacity in the lower Snake and Columbia River systems are, in part, reduced by eroded sediments entering the systems from upstream sources. Similarly, sedimentation that has reduced flow capacity in the upstream reach of the Lower Granite reservoir is a result of sediments flowing into the reservoir from the Snake and Clearwater Rivers. Sediments enter the river systems through a number of sources. Some erosion occurs as a natural physical process; however, land uses and land management practices also affect the amount of erosion and sediments entering the river system.

Studies have shown that non-irrigated cropland is a predominant land use in the watershed draining to Lower Granite reservoir and is responsible for approximately 37 percent of the sediment yield to the Lower Granite reservoir (Reckendorf et al., 1988). Other sources of sediment yield in the watershed include forest lands, streambank erosion, rangeland, irrigated farmland, and other land uses. Best management practices, including modified timber harvesting practices, erosion and sedimentation controls, and agricultural conservation reserve practices (e.g., creating riparian buffers, or removing highly erodable land from agricultural production) can reduce sediments entering the river systems and draining to the lower Snake and Columbia Rivers. Reckendorf et al. estimated in 1988 that implementation of Food Security Act conservation practices (e.g., the Conservation Program, which takes highly erodable land out of production) could reduce the overall sediment yield to Lower Granite reservoir by up to 37 percent.

The Corps owns and, in most locations, manages shoreline lands along the lower Snake and Columbia Rivers. However, it is not within the Corps' authority to control land uses and land management practices in the vast majority of the watershed that drains to the lower Snake and Columbia Rivers. While control of upstream land uses to control erosion and sedimentation is potentially part of a strategy to reduce sedimentation. This measure was considered useful in minimizing the need for other measures to fully meet the program purposes and was recommended for continued consideration and implementation through the LSMG.

2.2.2 Reservoir Drawdown

Reservoir drawdown was considered in two different ways to increase the flow conveyance capacity of the Lower Granite Dam Project in the Snake and Clearwater Rivers confluence area. Lower Granite reservoir was designed to operate at a pool elevation of 733 feet msl, while allowing the safe passage of flows through the confluence area at or below elevation 738. Over time, the sedimentation in the confluence area has affected the project's ability to pass flows at or below elevation 738. To correct this loss of conveyance capacity, first, an action, flow conveyance, was considered to draw the reservoir down in anticipation of high flows to reduce the pool or backwater affects on channel flow in the confluence area. This action would result in greater channel conveyance capacity with reduced water surface elevations and a lowered risk of flooding. Second, an action, sediment flushing, to periodically lower the reservoir at regular intervals was considered to increase the flow velocities in the confluence area and flush the sediments further down river to areas of excess conveyance capacity.

2.2.2.1 Flow Conveyance

The first drawdown measure considered to increase flow capacity at the confluence of the Clearwater and Snake Rivers adjacent to Lewiston, Idaho, was to draw down the Lower Granite reservoir to allow the SPF flow to pass without exceeding elevation 738. Lower Granite reservoir was designed to operate at a pool elevation of 733 feet msl, while allowing the safe passage of flows through the confluence area at or below elevation 738. Over time, the sedimentation in the confluence area has affected the project's ability to pass flows at or below elevation 738. Model studies have shown that Lower Granite reservoir is still able to pass up to 300,000 cfs (8 495.1 m³/s) flows both while maintaining a water surface elevation at the confluence of the Clearwater and Snake Rivers of 738 feet msl, and while maintaining 15 feet (4.6 m) of navigation clearance over the lock sills at Lower Granite. Flows above 300,000 cfs (8 495.1 m³/s), up to the SPF of 420,000 cfs (11 893.1 m³/s), are predicted to result in water surface elevations above 738 feet msl due to the influence of post-construction sedimentation in the confluence area and the existing dam. Accordingly, a reservoir drawdown would not lower the water surface elevation in the confluence area to or below 738 feet msl during flows of 300,000 cfs (8 495.1 m³/s) or greater.

2.2.2.2 Sediment Flushing

Drawdown of the Lower Granite reservoir below elevation 724 at the forebay, was considered for the purpose of flushing sediments downstream thus improving conveyance capacity and reducing shoals in the confluence area. Reservoir drawdown that would scour the historic river channel, thus potentially flushing sediments downstream, would be well below the authorized operating pool elevation of Lower Granite reservoir and would severely impact project uses. Based on the 1992 Lower Granite Reservoir drawdown, significant adverse impacts to public infrastructure (e.g., roads, drainage systems) and fish passage facilities at Lower Granite Dam would result from substantial drawdown needed to flush sediments. A drawdown alternative would also have an adverse effect on the navigation, causing a further reduction in the navigation clearances provided in the Lower Granite reservoir. This measure was eliminated from further consideration to meet the needs of this program.

2.2.3 In-Water Sedimentation Control

2.2.3.1 Bubble Curtain

Technologies are available that limit or prevent deposition of suspended sediments within a specific area. One such method involves using air or water circulation in the water column to keep sediments from depositing within a protected area, thus minimizing the need for dredging. Currently, the Port of Grays Harbor, Washington, uses this technology to prevent sedimentation around its terminal ship berths. Also, an "air curtain" can be generated from a submerged perforated pipe to contain sediments and keep them from settling.

This method is appropriate and effective for localized applications such as specific ports, boat basins, or other areas of limited size. However, these methods are not particularly applicable to the scope of navigation channel maintenance contemplated in the proposed plan. Use of either circulated water or air bubbles would require many miles of piping and numerous pumps and/or compressors. It would also require nearly constant operation, resulting in localized noise, air quality impacts, and ongoing system maintenance. Additionally, introduction of air into some areas of the lower Snake River would likely contribute to or exacerbate gas saturation. For these reasons, the use of bubble curtains was dismissed as neither a feasible nor reasonable alternative to address the plan's purpose and need.

2.2.3.2 Bendway Weir

Another method of cont rolling the sedimentation of the navigation channels to reduce dredging is the use of Bendway weirs. A Bendway weir is a well-engineered, environmentally sensitive approach to reducing streambank erosion and redirecting sediment flow to reduce costly maintenance. The concept for Bendway weirs was developed by the Waterways Experiment Station in 1988 and has been used to realign and stabilize a number of streams and rivers across the United States, including the Mississippi River. This method may have the potential to reduce the shoaling at critical points such as the Port of Clarkston navigation channel at RM 139 on the Snake River; however, it is not included as a part of the recommended plan without further consideration. The placement of these rock weir structures requires considerable care to achieve overall reduction in the sedimentation of the navigation system while avoiding adverse reductions in flow capacity. A successful weir installation requires thorough understanding of the Bendway weir theory and extensive knowledge of the river location where the structure is to be placed. The method may warrant further consideration as a method to prevent persistent shoaling, as experienced at the Port of Clarkston, but is not considered as a method to be adopted throughout the system to reduce sedimentation. Although it is likely that Bendway weirs could be designed to solve the local navigation problems, they would either trap additional sediment or move it only a short distance downstream. In addition, the weirs themselves would raise the water-surface profile. While Bendway weirs do not represent substantial, complete, or, in many cases, feasible stand-alone solutions to the issues addressed in the DMMP, the proposed adaptive management program provides an opportunity for on-going evaluation of these and other measures to address sedimentation and dredged material management issues. If this method were pursued, mathematical modeling of the hydraulic conditions with and without the Bendway weirs in place would be required to ensure maintenance of the flow conveyance capacity.

2.2.4 Dredging and Disposal of the Dredged Material

A range of dredging and disposal measures has been considered in formulating the alternatives presented in this plan. Most of these measures can be coupled with some degree of levee modification in the Lewiston-Clarkston area. The measures range from dredging to maintaining the authorized navigation channel and related facilities in the five reservoirs to dredging up to 2 million cy (1 529 110 m³) annually in the main river channel for improvement of flow capacity. Increasing dredging amounts in the Lower Granite reservoir at the confluence of the Clearwater and Snake Rivers was designed to provide proportionately increasing flow conveyance in that area. Figure 2-2 presents a schematic comparison of channel maintenance for flow conveyance and navigation clearance. Although the focus of the dredging program measures for increased flow conveyance is in the Lower Granite reservoir, the program measures also consider dredging in the other reservoirs in the lower Snake River system to maintain the navigation channel. All measures that contemplate volumes greater than that required for maintenance of the navigation channel apply only to the Lower Granite reservoir. All dredging measures include the maintenance of the navigation channels and related facilities in all five reservoirs with varying dredged material quantities for flow conveyance options in Lower Granite reservoir.

 

Dredging would be performed using either mechanical or hydraulic methods. Mechanical dredging with a clamshell dredge would be the preferred dredging method for the maintenance of the navigation channels and recreation facilities. Mechanical dredging involves excavation of sediments. A "clamshell" dredge generally involves a crane-mounted, hinged bucket to scoop up and move dredged material. Hydraulic dredging employs suction to move sediments. Hydraulic dredging may be considered for small areas off the main river channel, such as irrigation intakes.

The NMFS and Washington Department of Fish and Wildlife have not allowed use of hydraulic dredging methods for over 10 years because of concern for entrainment of juvenile ESA-listed endangered or threatened fish species. However, the agencies have indicated they would consider the use of hydraulic dredging for small, off-channel areas on a case-by-case basis.

2.2.4.1 Dredging With In-Water Disposal

When determining options and criteria to use for in-water disposal of dredged material for beneficial use, the Corps reviewed a study designed in 1987 by numerous scientists from federal, state, university and tribal entities. These entities included the Corps, USFWS, NMFS, ESSA, Battelle-PNNL, WDFW, ODFW, University of Idaho, University of Washington, Oregon State University, and the Yakima (now Yakama) Indian Nation (Web et al., 1987). The researcher involved with many of the studies was David Bennett, Ph.D., a tenured professor at the University of Idaho. The multiple-year study design, a lead researcher independent from the federal government, and study design from the region's leading experts yielded scientifically sound results for consideration in dredged material management planning as explained in the following sections.

Initially, in-water disposal of dredged material was considered to be in one of three types of areas: (1) shallow water, 0 to 20 feet (0 to 6.1 m) below the surface; (2) mid-depth water, 20 to 60 feet (6.1 to 18.3 m) below the surface; and (3) deep-water, 60 feet (18.3 m) and deeper. The selection criteria of the in-water disposal area usually included the physical characteristics of the material, the potential to optimize the benefit to fish, and the absence of known cultural resource sites. Once materials were placed aboard the bottom-dump barges, they would be judged for their suitability for use as fish habitat and assigned a disposal area. Samples taken from the barge while loading would be used to determine the appropriate disposal area. This plan called for disposing of material judged suitable for fish habitat, with at least 80 percent sand or larger [greater than 0.008 inch (0.2 millimeters (mm)) in diameter], at a shallow- or mid-depth water disposal area. Sands, gravels, and cobbles are expected to comprise 85 percent of the total dredged material. The remaining 15 percent of material that was silt or finer and, therefore, not suitable for fish habitat would be deposited in deep water directly from bottom-dump barges beginning at the upstream end of the designated deep-water disposal areas. Disposal of the silt in deep-water sites would have little impact, either positive or negative, on aquatic species. The capacities of these disposal sites exceed the quantity of dredged material expected from all sources in the next 20 years. Small amounts of material may require disposal at upland sites. While this plan would adequately dispose of the expected dredged material, it was not considered the optimum plan because the Clean Water Act specifies that placing fill within the waters of the United States should be avoided if there is a practicable alternative. However, Region 10 of the Environmental Protection Agency has stated that in-water disposal of dredged material would be acceptable if the material was used in a beneficial way.

A revised plan considered utilizing all of the dredged material for the creation of shallow water fish habitat rather than placing the fine sediment in the deep portions of the reservoir. The fine grain silts would be used in a mixture with sands and gravels to fill mid-depth areas and form the foundation for the later placement of sand and gravel for shallow-water habitat. In-water disposal sites designated for each of the reservoirs included shallow-water and mid-depth disposal areas that had no known cultural resource sites. The objective of this disposal plan is to establish shallow-water habitat from 0 to 20 feet (0 to 6.1 m) deep to restore fish habitat. Equipment limitations may restrict the disposal of material to at or below -10 feet (-3 m) in the near-shore shallow areas. While the formation of shallow water habitat of depths from 0 to 10 feet (0 to 3 m) is desirable, disposal of dredged material to form these shallow areas would be restricted to sites identified as suitable to provide an environmental restoration opportunity and where a sponsor is willing to share costs.

Juvenile fall chinook salmon prefer shallow, open sandy areas along shorelines for rearing (Bennett et al., 1997). Bennett et al. (1998) showed that fall chinook salmon utilized the shallow-water habitat created with in-water disposal of dredged material that surrounds Centennial Island in Lower Granite reservoir, near RM 120. In some years, as many as 10 percent of the total sample of subyearling chinook salmon from Lower Granite reservoir originated from the habitat created by in-water disposal. Bennett et al. (1998) reported that fall chinook salmon were most commonly collected over lower gradient shorelines that have low velocities and sandy substrate. Habitat having these physical characteristics can be effectively constructed in any of the lower Snake River reservoirs with appropriate placement of dredged material.

Differences in habitat suitability exist for habitat created by dredged material depending upon substrate size. For example, at the Centennial Island site in Lower Granite reservoir, the shoreward station with sandy substrate often supported a different fish community structure than that from the channel side that was armored with cobble/boulders to secure the shoreline. Species that prefer larger substrate, such as smallmouth bass, were consistently collected in higher abundance along the large substrate than in the area with finer substrate, without armoring of larger substrate. Therefore, preliminary data suggest that fish community structure can also by "fine tuned" with manipulation of the size of substrate as well as changes in depth.

A contingency upland disposal site has also been identified for each alternative to provide storage for a portion of dredged material that may, for whatever reason, need to be deposited on a separate upland site. In the event that dredged material may be unsuitable for in-water disposal (e.g., dredged material that may contain low levels of contaminants that prohibit its use for in-water habitat creation, but would not otherwise be considered solid or hazardous waste), it would be placed at the Joso upland disposal site, and appropriate confinement measures would be taken to isolate it.

The Joso upland disposal contingency site is located on the south shore of the Snake River between RM 56.5 and RM 58.6, in the Lower Monumental reservoir (plate 11). This document presents the conceptual design for development of this site and disposal plans for dredged material at this site should the need occur in the future. The Joso site is designated as a wildlife HMU, but was formerly used as a borrow site and contains a gravel pit at its center. It is estimated that this site can accept the full amount of material from all five reservoirs through the 20-year life of this DMMP/EIS. The initial construction of the site would include reestablishing the barge berth at the west end of the site. A temporary storage area would be developed by constructing a containment berm around an area adjacent to the barge berth. Permanent disposal would be developed in the old gravel pit area in the center of the Joso site. Dredged material would be off- loaded at the site using a barge- mounted crane and mobile transport equipment to haul material from temporary storage to the permanent disposal site. The Corps would conduct tests on material to be dredged and prepare final design of the permanent disposal features before disposing of material at the Joso site.

Below are descriptions of the four options of dredging that were considered for this DMMP/EIS. The main differences between the options are the quantity of material to be dredged and the dredging template design.

2.2.4.1.1 Navigation and Facility Maintenance Dredging

Dredging Areas. The maintenance dredging area is the current authorized navigation channel for the lower Snake River and McNary reservoirs and maintenance of public recreation areas, such as swimming beaches and boat basins, and irrigation intakes for wildlife HMU's managed by the Corps.

Dredging Template Design. As noted above, the dredging template is based on the authorized navigation channel, public recreation areas, and irrigation intakes for HMU's. The authorized navigation channel is 250 feet (76.2 m) wide and 14 feet (4.3 m) deep for all five reservoirs. The template would not extend down into original riverbed or shoreline material.

Disposal Sites. In-water locations for shallow, mid-depth, and deep water dredged material disposal are identified in each of the five reservoirs. In-water disposal areas in Ice Harbor and Lower Granite reservoirs used in the recent maintenance dredging operations have created mid-depth and shallow-water sites. The methods used in these latest disposal operations would be employed in this base plan and applied to all five reservoirs. Dredged material containing sand, gravel, and cobbles would be disposed of in either mid-depth, as a base, or shallow water to create shallow water habitat. Silts and fine material would be restricted to disposal at mid-depth sites. Collectively, the designated in-water disposal sites have adequate capacity to contain all materials dredged under this option.

Upland disposal may be used for some of the recreation area dredging and irrigation intake dredging on a case-by-case basis. Disposal would likely be adjacent to the dredging site.

Material Types and Volume. Dredged materials consist of silts, sands, gravels, and cobbles. Historically, composition of dredged material from the study area has been approximately 85 percent sand, gravels, and cobbles, and approximately 15 percent silts and fines. A volume of dredged material up to 340,000 cy (259 948.7 m³) would be dredged from the five reservoirs about every 2 years over the next 20 years for a total volume of up to 3,400,000 cy (2 599 487 m³) of dredged material.

Program Schedule and Duration. For planning purposes, it was assumed that maintenance dredging using a clamshell dredge would be conducted every 2 years in each reservoir. However, the length of time between actual dredging operations will vary depending on sediment inflow and deposition. Dredged materials would be transported by bottom-dump barge to the appropriate in-water disposal sites. Dredging would usually occur between December and March 1 in the Snake River and between December 1 and March 31 in the Columbia River during periods (windows) established to minimize the impacts on ESA- listed endangered or threatened anadromous fish species. Dredging in the summer, possibly in August, would be considered on a case-by-case basis for off-channel dredging. Dredged material containing predominantly sands, gravels, and cobbles would be transported by bottom-dump barge to the shallow and mid-depth areas for in- water disposal. Barges containing silt and other fines would be restricted to disposal at mid-depth sites. A minimum water depth of 15 feet (4.6 m) is required for bottom-dump barges to access the disposal sites. Disposal would be done by bottom-dump barge at a rate of approximately 15,000 cy per acre (28 338 m³ per hectare) to create shallow water habitat with a minimum depth of 10 feet (3 m). A drag beam or some other device would be used to smooth the surface of the material dumped from the bottom-dump barges. Figures 2-3 and 2-4 illustrate the disposal process. Channel maintenance average annual costs are estimated at $560,000 computed over the 20-year period at a 6.875 percent interest rate. This cost estimate is based on maintaining the authorized navigation channel dimensions over the next 20 years using clamshell dredging, bottom-dump barges, and in-water disposal of the dredged material. Use of hydraulic equipment was not considered acceptable because of the anticipated adverse impact on endangered fish resources. Disposal at upland sites instead of in-water sites was considered, but found to be more costly and provide less environmental benefit than in-water disposal.

 

 

2.2.4.1.2 Dredge 300,000 cy Per Year

Dredging Areas. This option would meet the requirements for navigation maintenance in each of the five reservoirs as well as improve the flow conveyance capacity of the Lower Granite reservoir. Dredging to improve flow conveyance capacity would be conducted only in the Lower Granite reservoir. Navigation maintenance dredging described above would remain unchanged. Dredging in Lower Granite reservoir would extend from the Port of Wilma near Snake RM 134 to the U.S. Highway 12 bridge located upstream of the confluence of the Snake and Clearwater Rivers, near Snake RM 139.5. The Clearwater River dredging would extend from the Snake River confluence upstream approximately 1.5 miles (2.4 km) to the Port of Lewiston.

Dredging Template Design. Dredging templates for all of the reservoir areas except the Snake/Clearwater Rivers confluence area of the Lower Granite reservoir would remain the same as the navigation and facility maintenance dredging option. The Snake/Clearwater Rivers confluence area dredging template would increase in size and vary in width from 300 feet (91.4 m) near the Port of Wilma to 1,700 feet (518.2 m) in the Clearwater River confluence area. This portion of the template is a large volume to be dredged over multiple years to improve flow conveyance as well as provide navigation clearances. The average dredging width on the Snake River within this area would be 750 feet (228.6 m). The average depth of dredging on the Snake River would be approximately 10 feet (3 m) below the elevation of the bottom of the river channel as it existed in 1997 and would extend down into original riverbed or shoreline material.

Disposal Sites. Disposal areas for all reservoirs would remain the same as the navigation and facility maintenance dredging option and have adequate capacity to contain all materials dredged under this option. In-water disposal in Lower Granite reservoir would be accomplished downstream of Centennial Island near Snake RM 120.4.

Material Types and Volume. Dredged materials would be composed of a mixture of silts, sands, gravels, and cobbles. Approximately 6.4 million cy (4.9 m³) would be dredged from the five reservoirs over the next 20 years and 23.1 million cy (17.6 m³) between the years 2002-2074. Program Schedule and Duration. Dredging would usually occur from December 15 to March 1 for the Snake River reservoirs and December 1 to March 31 for the McNary reservoir. Dredging in the summer, possibly in August, would be considered on a case-by-case basis for off-channel dredging.

Approximately 300,000 cy (229 366.5 m³) of material would be dredged annually throughout the study period from the Lower Granite reservoir for flow conveyance and navigation maintenance dredging. Navigation channel maintenance dredging of 40,000 cy (30 582.2 m³) from the other four reservoirs would occur about every 2 years, as previously described. The average annual cost of this measure computed over the period 2001 to 2074 at 6.875% interest is $1,233,000.

2.2.4.1.3 Dredge 1 Million cy (764 555 m³) Per Year

Dredging Areas. This option would meet the requirements for navigation and facility maintenance in each of the five reservoirs as well as improve the flow conveyance capacity of the Lower Granite reservoir. Only the Lower Granite reservoir dredging area and template would change. Dredging in the Lower Granite reservoir would extend from the Port of Wilma near Snake RM 134 to the U.S. Highway 12 bridge located upstream of the conflue nce of the Snake and Clearwater Rivers, near Snake RM 139.5. The Clearwater River dredging would extend from the Snake River confluence upstream 1.5 miles (2.4 km) to the Port of Lewiston. Navigation maintenance dredging of the channel would occur in the other reservoirs.

Dredging Template Design. The dredging template would be the same as the 300,000 cy (229 366.5 m³) alternative. The Snake/Clearwater Rivers confluence area dredging template varies in width from 300 feet (91.4 m), near the Port of Wilma, to 1,700 feet (518.2 m) in the Clearwater River confluence area. The average dredging width on the Snake River within this area would be 750 feet (228.6 m). The average depth of dredging on the Snake River would be approximately 10 feet (3 m) below the elevation of the bottom of the river channel as it existed in 1997 and would extend down into original riverbed or shoreline material. It would take fewer years to remove material from the template than for the 300,000 cy (229 366.5 m³) dredging alternative.

Disposal Sites. Disposal sites identified in the navigation and facility maintenance dredging option are adequate to contain all materials dredged under this option.

Material Volume and Types. Dredged materials would be composed of a mixture of silts, sands, gravels, and cobbles. Approximately 13.7 million cy (10 474 400 m³) would be dredged from the five reservoirs over the next 20 years and more than 31.8 million cy (24,351,210 m³) dredged between the years 2001 and 2074 under this option.

Program Schedule and Duration. Dredging would usually occur from December 15 to March 1 for the Snake River reservoirs and December 1 to March 31 for McNary reservoir. Dredging in the summer, possibly in August, would be considered on a case-by-case basis for off-channel dredging. Approximately 1 million cy (7 64 555 m³) of material would be dredged annually from Lower Granite reservoir for a 10-year period to establish the Lower Granite dredging template area described above. The dredging activity would then drop back to 325,000 cy (248 480 m³) annually for the remainder of the study period through the year 2074 to ensure the template is maintained for the period. For planning purposes, it was assumed that navigation channel maintenance dredging of 40,000 cy (30 582.2 m³) from the other four reservoirs would occur every 2 years. The average annual cost of this measure is $1,911,000 when computed at 6.875% interest over the period 2001 to 2074.

2.2.4.1.4 Dredge 2 Million cy (1 529 110 m³)Per Year

Dredging Areas. This option would meet the requirements for navigation and facility maintenance in each of the five reservoirs as well as improve the flow conveyance capacity of the Lower Granite reservoir. Only the Lower Granite reservoir dredging area and template would change from the 1 million cy (764 555 m³) per year measure. Dredging in the Lower Granite reservoir would extend further downstream from the vicinity of Silcott Island near Snake RM 131 upstream to the U.S. Highway 12 bridge upstream of the confluence of the Snake and Clearwater Rivers, located near Snake RM 139.5. The Clearwater River dredging areas extend from the Snake River confluence upstream to the Port of Lewiston at Clearwater RM 1.66.

Dredging Template Design. The proposed Lower Granite reservoir template on the Snake River is larger than the previous alternative and would vary in width from 600 feet (182.9 m) near Silcott Island to 1,700 feet (518.2 m) in the confluence area. The average width on the Snake River is 950 feet (289.6 m). The Clearwater dredging template varies in width from 300 feet (91.4 m) near the Camas Prairie Railroad bridge crossing to 1,000 feet (304.8 m) in the Port of Lewiston turning basin. The average width is 750 feet (228.6 m). The average depth of dredging would be 20 feet (6.1 m) below the elevation of the bottom of the river channel as it existed in 1997 and would extend down into original riverbed or shoreline material.

Disposal Sites. Disposal sites identified in the navigation and facility maintenance dredging option (section 2.2.4) would be adequate to contain all materials dredged under this option.

Material Types. Dredged materials would be composed of a mixture of silts, sands, gravels, and cobbles. Approximately 40.4 million cy (30.9 m³) would be dredged from the five reservoirs in the next 20 years and approximately 79.2 million cy (60.6 m³) between the years 2001 and 2074 under this option.

Program Schedule and Duration. Dredging would usually occur from December 15 to March 1 for the Snake River reservoirs and from December 1 to March 31 for the McNary reservoir. Dredging in the summer, possibly in August, would be considered on a case-by-case basis for off-channel dredging. Approximately 2 million cy (1.5 m³) of material would be dredged annually for a 20-year period to establish the dredging template area described above. The dredging activity would then be reduced to 725,000 cy (554 302.3 m³) annually for the remainder of the study period through the year 2074 to ensure the dredging template remains clear of sediment. For planning purposes, it was assumed that dredging of 40,000 cy (30 582.2 m³) total from the other four reservoirs would occur about every 2 years. The average annual cost of this measure when computed over the period of 2001 to 2074 at 6.875% interest is $4,706,000.

2.2.4.2 Dredging with Upland Disposal

This measure employs the same dredging equipment and operation methods as the previous measures, but uses a standard barge 240 feet (73.2 m) long by 42 feet (12.8 m) wide to transport the dredged material. The dredged material would either be transferred directly to an upland disposal site or stockpiled at a temporary site for future transfer to a permanent upland disposal site. This measure includes navigation and facility maintenance dredging in the McNary reservoir and in the four lower Snake River reservoirs.

As part of the DMMS process, the Corps identified multiple upland sites on each reservoir that could potentially serve as dredged material disposal areas. A preliminary screening of these sites was conducted to assess their feasibility and/or suitability to serve as sites for upland disposal of dredged material. This screening process narrowed the list of potential sites to a total of 10 sites: a primary and secondary upland site in each of the five reservoirs. Anticipated costs and impacts of these 10 primary and secondary sites were used to further screen and narrow the list of potential upland sites to three: the Joso site (plate 11) and Page Creek disposal site (1 mile south of Snake RM 131), and the Chief Timothy "transfer site" (Snake RM 130.5).

All upland disposal options would include a contingency upland disposal site, similar to the in-water options, for material found unsuitable for disposal in the standard upland disposal site. This site has been identified as Joso (plate 11), located on the south shore of the Snake River (between RM 56.5 and RM 58.6) in the Lower Monumental reservoir.

The alternatives that involve upland disposal of va rying dredged material volumes are described below.

2.2.4.2.1 Navigation and Facility Maintenance Dredging

All material would be disposed in the Joso upland disposal site. The Joso site is located along the southern shore of the Snake River between RM 56.5 and RM 58.6, in the Lower Monumental reservoir. The site is bounded on the south side by the Union Pacific Railroad. The entire site is approximately 568 acres (229.9 hectares) and is constrained by a habitat area approximately 600 feet (182.9 m) wide along the Snake River site boundary and by wetlands in the eastern corner. With the 600- foot (182.9- m) riparian boundary protected, the Joso site provides a barge slip, material unloading areas, and an area of approximately 280 acres (113.3 hectares) for permanent disposal of dredged material. A portion of the permanent disposal area would be set aside as a confined area, with a liner, to accommodate the material found to be unsuitable for disposal in the standard upland disposal area.

The Joso site would receive dredged material by barge and permanently store up to 6.4 million cy (4.9 m³) of material. The site is adequate to hold all of the navigation and facility maintenance dredged material from the five reservoirs over the 20-year maintenance period. Barge access to the site would be provided by reestablishing the berth at the west end of the site. Anchored sheet pile walls would be used along the barge slip sides to provide vertical wall docking surfaces and to retain the adjacent platform walls. Barge tie-offs would be constructed at the top of the slip adjacent to the sheet pile. Temporary dredged material dewatering and storage areas with containment berms and detention ponds would be developed adjacent to the slips. Material handling at the Joso site would include off- loading of dredged material from the barges using cranes on rubber tires. The material would be placed in the temporary storage area adjacent to the barge slip for dewatering and loading onto trucks for transport into the disposal area. The material would then be placed in lifts with track-type tractors and compacted, resulting in a large structural fill conforming to the established final topography for the disposal area. All disposal activities would avoid known cultural resource sites. Areas that reach final grades would be restored on a periodic basis by placing 6 inches (15.2 cm) of topsoil and re-seeding to achieve a vegetative cover similar to surrounding site areas. A conceptual site layout for the Joso site is presented in figure 2-5 and described in detail in appendix D, Upland Disposal Conceptual Design.

 

2.2.4.2.2 Dredge 300,000 cy Per Year

For the first 20 years of the program, most material dredged under this option would be deposited in the Joso site. At the conclusion of the 20-year period, the Joso site would be filled to capacity and another site would have to be developed.

The Page Creek site in Lower Granite reservoir would be used to hold the remaining material once Joso is filled. The Page Creek disposal site is located approximately 1.5 miles (2.4 km) south of the Snake River adjacent to Page Creek near the mouth of Alpowa Creek, downstream of Snake RM 130. The entire site is approximately 985 acres (398.6 hectares), but only a portion of the site, at the northern end, would be used for disposal of dredged material. The site has a capacity of 80 million cy (61 164 390 m³) and is capable of containing all the material expected to be dredged for all alternatives considered over the life of the project to year 2074.

The site has a plateau on the northern portion that is presently used for agricultural crops. The remainder of the site has relatively steep slopes from the plateau down to Page Creek, a drop of about 600 vertical feet (182.9 vertical meters). Dredged material would be placed in lifts starting at the lower end of the northerly portion of the site and would progressively fill the site in a southerly direction. Fill placement operation would use track-type tractors and steel- wheeled compactors. The disposal and fill construction operation would take place throughout the year. Site restoration would occur periodically throughout the life of the fill construction.

Use of the Page Creek site would require development of a transfer facility on the left bank of the Snake River, located adjacent to Chief Timothy State Park at RM 131, that would allow barge off- loading, staging of dredged material, and facilities for transporting material across U.S. Highway 12 to the Page Creek site. The Chief Timothy transfer site was proposed to meet this need. The Chief Timothy site, an open water embayment, is an area of about 66 acres (26.7 hectares) in 21 feet (6.4 m) of water located at the mouth of Alpowa Creek in the Snake River. The facility would consist of a rock berm around the site perimeter with a top elevation 3 feet (0.9 m) above normal operating pool for the Lower Granite reservoir. The interior of the berm would be filled with approximately 2 million cy (1 529 110 m³) of dredged material to form a platform of dredged material for a temporary storage area. A barge berthing area would be developed and gantry-type cranes installed for off- loading barges. The transfer of up to 2 million cy (1 529 110 m³) per year of dredged materials to the Page Creek disposal site would require the construction of a bridge across U.S. Highway 12. The Page Creek and Chief Timothy sites are described in more detail in appendix D, Upland Disposal Conceptual Design. The average annual cost of this measure computed over the period 2001 to 2074 at 6.875% interest is $5.6 million.

2.2.4.2.3 Dredge 1 Million cy (764 555 m³) Per Year

This plan would use the Chief Timothy transfer site and the Page Creek disposal site for dredged material from Lower Granite reservoir for the entire period. The Joso site would be used for disposal of dredged material from McNary, Ice Harbor, Lower Monumental, and Little Goose reservoirs. The average annual cost of this measure computed over the period 2001 to 2074 at 6.875% interest is $6.8 million.

2.2.4.2.4 Dredge 2 Million cy (1 529 110 m³) Per Year

This plan would use the Chief Timothy transfer site and the Page Creek disposal site for dredged material from Lower Granite reservoir for the entire period. The Joso site would be used for disposal of dredged material from McNary, Ice Harbor, Lower Monumental, and Little Goose reservoirs. The average annual cost of this measure computed over the period 2001 to 2074 at 6.875% interest is $19.3 million.

2.2.4.3 Beneficial Use of Dredged Material

Dredged material can be used to benefit and restore the environment. This use is consistent with Corps policy to secure the maximum practicable benefits through the use of material dredged from navigation channels. Opportunities to use dredged material beneficially become available over time and cannot be anticipated in a programmatic document such as this. In order to be able to take advantage of such beneficial uses, this document sets forth a process to identify and evaluate the opportunities as each major dredging activity is being planned. Part of this process is the formation of an LSMG that would help identify beneficial uses such as creation of aquatic and wildlife habitat, replenishment of beaches, or filling of upland sites.

The LSMG described in section 1.8 would provide an interagency approach to management of dredged material including definition of disposal plans coordinated with and amenable to the public stakeholders and resource agencies. In accomplishing this function, the LSMG would facilitate a process involving participation of affected agencies, organizations, and groups to identify and recommend the most environmentally sound and practical beneficial use of dredged material for each major dredging activity.

Each time a dredging activity covered under this DMMP/EIS is planned, the following steps would be followed:

• The Corps would notify parties such as the ports, municipalities, environmental groups, agencies, and others known to have an interest in the beneficial use of dredged material. The Corps would provide the location, estimated quantity, dredging method, expected characteristics of dredged material and estimated time of the dredging activity. The Corps notification would precede the proposed dredging activity by allowing sufficient time to negotiate an agreement with a local sponsor for the beneficial use of the dredged material.

• A public notice would be published and distributed prior to the dredging activity. Beneficial uses defined by this process may be achieved when a local sponsor is willing to contribute a share of the cost. Table 2-2 describes the various measures and cost-sharing options that apply to the beneficial use of dredged material.

The cost of a "beneficial use of dredged material" project is determined to be the difference in disposal costs of the "beneficial use project" compared to the cost of the least-cost, environmentally acceptable dredged material disposal option. This DMMP/EIS identifies the basis for determining the least-cost option for dredged material disposal. At any time, the Corps can identify another beneficial use, and the non-Federal interest would be given reasonable opportunity to finance the additional cost.

In specific circumstances, the Corps has the authority and appropriations to go forward with a beneficial use without a local sponsor (i.e., woody riparian).

The opportunities that currently exist and were considered for early implementation are presented section 2.5.4.

2.2.4.4 Emergency Dredging

Under any dredging and dredged material disposal measure considered, the Corps may need to perform dredging on an emergency basis. An emergency, as defined in 33 CFR 335.7, Operation and Maintenance of Army Corps of Engineers Civil Works Projects Involving the Discharge of Dredged or Fill Material into Waters of the U.S. or Ocean Waters, is a situation that would result in an unacceptable hazard to life or navigation, a significant loss of property, or an immediate and unforeseen significant economic hardship if corrective action is not taken within a time period less than the normal time needed under standard procedures.

There are several potential situations that could occur in the Snake and Columbia Rivers that may require emergency dredging. High flows could deposit enough sediment at a point or points in the Federal navigation channel to block navigation. Rock could be swept into the navigation lock approach and form a shoal or sediment could build up on the inside bend of the navigation channel, posing an unacceptable navigation hazard.

For an emergency dredging situation, the Corps would perform environmental coordination on an expedited basis. The Corps would perform as much coordination as possible before initiating the emergency dredging, but some coordination may be performed during the dredging or after the dredging is completed.

2.2.5 Construct Upstream Sediment Traps

A qualitative evaluation of sediment control structures was conducted to assess structures that might provide sufficient control of sediment transport on the Clearwater and Snake Rivers. The objective was to identify structures that reduce the sediment load sufficiently to avoid dredging and/or levee raises in the Lewiston-Clarkston area. This, in turn, would mitigate the probability of flooding due to sediment deposition. Sediment control structures must slow velocities for a sufficient length of time to allow sediment to drop out of the water column and be deposited behind the control structures.

The U.S. Geological Survey (USGS) has estimated the amount of sediment being transported annually to be 1.9 million tons (1.72 million metric tons) in the Snake River at Lewiston, and 0.47 million tons (0.43 million metric tons) in the Clearwater River. Sediment sampling in Lower Granite reservoir found that approximately 95 percent of the sediments being deposited are fine- grained materials [typically smaller than 0.01 inch (0.25 mm)]. The relatively small size of the sediment material suggests that a submerged structure, such as a silt trap, would be marginally effective. The Corps investigated the possibility of dredging an area of the Snake River sufficiently to form a reservoir of slack water where sediments could settle. These investigations determined that the amount of material that would need to be dredged was so great that the scenario was determined impracticable. Data also suggests that the existing dams and reservoirs on the lower Snake River retain approximately 80 percent of the sediments that enter the reservoir. It is unlikely that a new structure would be capable of better performance.

Estimates imply that removal of 80 percent of the sediment transported down the Snake River [approximately 1.5 million tons (1.36 million metric tons) per year] would be sufficient to mitigate sediment deposition concerns in the Lewiston-Clarkston area, excepting some deposition in a few areas that would adversely affect barge traffic. Therefore, it would not be necessary to construct structures on both the Snake and Clearwater Rivers.

The dredged material removed from the navigation channels in Lower Granite reservoir are composed of 85 percent sand, gravels, and cobbles and 15 percent finer silt material. This would suggest that the majority of the material entering this reservoir as silt does not contribute significantly to shoaling of navigation channels. This silt is either deposited in other portions of the reservoir or relocated by prop wash from navigation activities, eliminating it from the navigation channels. Since the larger materials (sand, gravels, and cobbles) are the sediment of primary concern to navigation channels, it is assumed that a smaller sediment trap might be capable of trapping a sufficient amount to be an economical alternative to dredging the channel. However, the legislative history concerning further structures on the Snake River for this purpose would indicate that this is not an acceptable alternative.

It is clear from the legislation passed since the authorization of Asotin Dam that Congress now intends no further Federal dam structures immediately upstream of Lower Granite on the Snake River. Portions of both the Snake and Clearwater Rivers have been identified in the Wild and Scenic River Act [PL 90-542, as amended, 16 United States Code (U.S.C.) 1271-1287] as rivers with sections that have been protected from further development or have qualities that make them candidates for protection. Public Law 94-199, dated December 31, 1995, de-authorized Asotin Dam because of its location with respect to the Hells Canyon National Recreation Area. Public Law 100-677, dated November 17, 1988, further prohibits the licensing of any dam, diversion, or bypass under the Federal Power Act on the Snake River above Lower Granite reservoir including the Asotin Dam site.

In addition to the clear legislation prohibiting Federal involvement, local, state, and Federal regulators indicate that there is no adequate justification for constructing a sediment detention structure on the Snake River near Asotin. The plan to construct a sediment detention structure has, therefore, been removed from further consideration.

2.2.6 Levee Modification

The cities of Lewiston and Clarkston are adjacent to the Lower Granite reservoir. Lewiston is protected by a backwater levee system installed in lieu of relocating its business district. The levee system is an upstream extension of the dam and was designed to allow the Lower Granite reservoir to be operated to protect the Lewiston and Clarkston area from inundation during the SPF.

The upper reach of the Lower Granite reservoir collects much of the sediment carried in suspension in the free- flowing reaches of the upstream rivers. Sediment accumulation in the reservoir over time has reduced the flow conveyance capacity in this upper reach and has compromised the level of protection provided by the levees. Dredging has been performed over the recent past to restore and retain flow capacity in this upper reach of Lower Granite reservoir.

Consideration was given to a variety of levee modifications including raising the levees and moving the levees back from the river to allow for a greater flow conveyance. Four levee modification plans were selected for further consideration based on their ability to provide the flow conveyance capacity most effectively with the least impacts. Concept designs and cost estimates were developed for the four levee raises, nominally identified as 12- foot (3.7-m), 8-foot (2.4- m), 4-foot (1.2- m), and 3- foot (0.9- m) raises, and the increased flow conveyance capability has been identified for each.

The following sections describe each of the levee raise plans.

2.2.6.1 The 12-Foot (3.7-m) Levee Raise

The 12- foot (3.7- m) levee raise involves constructing bin walls and earth embankment raises of existing levees, extending the existing levees in certain areas, and constructing new levees in some locations. The plan would include:

• Raising a portion of the west, east, and north Lewiston levees and building a new levee at the city of Asotin.

• Modifying U.S. Highway 12, County Road 900 along the north bank of the Snake River opposite Clarkston, Highway 129 along the west bank of the Snake River at Clarkston, Red Wolf Bridge access in northwestern Clarkston, Snake River Avenue along the east bank of the Snake River at Lewiston, and the Snake River Road above Asotin.

• Implementing changes to the Clarkston Sewage Treatment Plant, Asotin Sewage Treatment Plant, Lewiston Sewage Treatment Plant, and Lewiston Water Intake.

• Raising the U.S. Highway 12 bridge between Lewiston and Clarkston, the Camas Prairie Railroad (CPRR) bridge crossing the Clearwater River at Lewiston, the Memorial Bridge over the Clearwater River at Lewiston, the Asotin Memorial Bridge, the Highway 129-10 bridge, and the pedestrian bridge.

• Raising the CPRR track in Lewiston.

• Decreasing the risk of flooding to facilities including, but not limited to, the Ports of Wilma, Lewiston, and Clarkston.

• Increasing the risk of flooding at the following recreational areas: Hellsgate State Park on the Snake River opposite Asotin, Swallows Park between Asotin and Clarkston, Chief Timothy State Park on the south bank of the Snake River west of Clarkston, the county boat ramp on the north bank of the Clearwater River near RM 3, bike and walking trails along many of the levee segments, and the Clarkston Golf Course at the west end of Clarkston; as well as Rooster's Landing Restaurant, the convenience store and restaurant at Hellsgate State Park, a U.S. Forest Service building at Swallows Park, and the Corps' resource buildings at Clarkston.

• Possibly purchasing several residences along Highway 129.

The construction cost estimate for this plan is $87,661,500. The details for this plan are presented in appendix E, Lewiston Levee Modification Extension Analysis.

2.2.6.2 8-Foot (2.4-m) Levee Raise

The 8- foot (2.4- m) levee raise involves constructing bin walls and raising the earth embankment of existing levees, extending some existing levees, and constructing new levees in some locations. The plan includes:

• Raising the west, east, and north Lewiston levees and building a new levee at the City of Asotin.

• Modifying U.S. Highway 12, County Road 900, Highway 129, Snake River Avenue, and Snake River Road above Asotin.

• Implementing changes to the Asotin Sewage Treatment Plant and Lewiston Sewage Treatment Plant.

• Raising the U.S. Highway 12 bridge between Lewiston and Clarkston, the CPRR bridge, the Memorial Bridge, the Asotin Memorial Bridge, the Highway 129-10 bridge, and the pedestrian bridge.

• Raising the CPRR track.

• Decreasing the risk of flooding to facilities including, but not limited to, the ports of Wilma, Lewiston, and Clarkston.

• Increasing the risk of flooding at the following recreational areas: Hellsgate State Park, Swallows Park, Chief Timothy State Park, the county boat ramp on the Clearwater River near RM 3, and bike and walking trails along the levees, as well as Rooster's Landing Restaurant, the convenience store and restaurant at Hellsgate State Park, the U.S. Forest Service building, and the Corps' resource buildings.

2.2.6.3 4-Foot (1.2-m) Levee Raise

The 4-foot (1.2-m) levee raise involves constructing bin walls and raising the earth embankment of existing levees. The plan would include:

• Raising a portion of the west and north Lewiston levees.

• Modifying Highway 129 and Snake River Road above Asotin.

• Raising the U.S. Highway 12 bridge between Lewiston and Clarkston, the Camas Prairie Railroad (CPRR) bridge, and the Memorial Bridge.

• Decreasing the risk of flooding to facilities at the Port of Lewiston.

• Increasing the risk of flooding at the following recreational areas: Hellsgate State Park and Swallows Park, as well as Rooster's Landing Restaurant, the convenience store at Hellsgate State Park, the U.S. Forest Service building, and the Corps' resource buildings.

The construction cost estimate for this plan is $15,623,500. The details for this plan are presented in appendix E, Lewiston Levee Modification Extension Analysis.

2.2.6.4 3-Foot (0.9-m) Levee Raise

The 3- foot (0.9- m) levee raise involves adding an earth embankment raise to existing levees. The plan would include:

• Raising a portion of the west Lewiston levee.

• Modifying Highway 129 and the Snake River Road upstream of Asotin.

• Increasing the risk of flooding at the following recreational areas: Hellsgate State Park and Swallows Park, as well as the convenience store at Hellsgate State Park, the U.S. Forest Service building, and the Corps' resource buildings.

The construction cost estimate for this plan is $2,273,500. Details are presented in appendix E, Lewiston Levee Modification Extension Analysis.

2.3 FORMULATION OF ALTERNATIVES TO BE CONSIDERED IN DETAIL

2.3.1 Screening Process

The screening process consisted of formulating alternatives from the most viable program measures discussed in section 2.2, evaluating each alternative, and selecting alternatives for further detailed consideration. Preliminary evaluation criteria were developed to determine the alternatives that were feasible, reasonable, and should be considered in detail. These criteria considered whether:

• The alternatives were cost-effective, while either providing environmental benefits or causing the least environmental damage.

• The alternatives provided a way to regain and/or maintain channel capacity to provide an acceptable level of flow conveyance capacity resulting in flood protection (based on the results of a risk-based analysis) in the Lewiston-Clarkston area.

• The alternatives have acceptable impacts on other project uses (such as shippers and recreational users).

A set of detailed screening criteria was then developed to evaluate the relative impacts, costs, and/or benefits of a set of dredging and levee alternative combinations. Use of these criteria in an evaluation process facilitated a selection of alternatives that were considered feasible, reasonable, and would be evaluated in detail in the EIS. An initial set of 12 dredging and levee alternatives included the "No Action (No Change) alternative" and combinations of dredging and levee raises. Ten alternatives go beyond navigation maintenance by combining increased dredging and levee raises to meet approximately the same levels of navigation and flow conveyance needs. The methodology and criteria used to evaluate each of the 12 alternatives against the screening criteria are discussed below.

2.3.2 Methodology and Evaluation Criteria

A set of evaluation criteria was established that allowed an across-the-board comparison of the 12 alternatives. The criteria were chosen because they represented key indicators of environmental impacts and economic benefits and costs. These criteria also pointed out potential "fatal flaws" in an alternative and allowed a planning- level comparison of the alternatives. Using this process, high-cost, high- impact alternatives were dismissed and low-cost, low-impact alternatives were advanced for further consideration. The evaluation criteria are listed in table 2-3.

The criteria were divided into three categories or "tiers" based upon their relative priority as indicators of the advantages or constraints of each alternative. The following sections provide details of how each criterion was applied through the screening process.

2.3.2.1 Expected Annual Damages

The estimated level of flood damage reduction provided by the alternatives for Lower Granite reservoir was analyzed based on the elevations of the structures in the floodplain and on simulated water surface profiles for the alternatives. No distinction was made in this preliminary screening between the flood damage reduction of the two dredged material disposal methods considered (e.g., in-water or upland disposal of dredged material).

The evaluation was based on the results of a risk-based, flood damage assessment computer model study. This flood damage assessment considered the hydrologic statistical risk of floods, hydraulic variations in flood flow water surface elevations, and associated damages to various types of buildings, structures, and activities in the floodplain.

2.3.2.2 Average Annual Costs

The present value of future costs for each alternative was calculated from the total costs of dredging, disposal of dredged material, and construction of the proposed levee raises over the projected lives of the alternative scenarios and the estimated phasing of construction, operation, and maintenance over that period. The alternatives were compared based on the present value of future costs over a 74-year period computed at an interest rate of 6.875 percent. The interest rate used for discounting is the current Department of the Interior rate to be used for Federal water resource planning purposes (63 FR 63329). Table 2-4 presents a summary of average annual costs of plan measures.

2.3.2.3 Endangered Species

Listings of endange red species were obtained from the NMFS and U.S. Fish and Wildlife Service (USFWS). Habitat requirements, timing of occurrence, and the potential location of listed species relative to the dredging and disposal sites were determined. A potential impact determination was made based on the likelihood of ESA- listed individuals being present or if required habitat was in the project vicinity. If no individuals were likely to be present or no habitat existed, a "no effect" determination was made. If habitat was available, but because of timing of the project the species would not be present, a determination of "may affect but not likely to adversely affect" was made. If habitat was available and individuals could be present, a determination of "may affect and likely to adversely affect" was made. Biological Assessments (BAs) were prepared and sent to both the NMFS and USFWS. Copies of the BAs along with documentation of consultation activities with NMFS and USFWS can be found in appendices F and G.

In the case of salmonids, certain in- water disposal alternatives have the potential for improving habitat conditions. In these cases, the mitigation was assumed and a beneficial impact was determined to occur.

2.3.2.4 Hazardous, Toxic, and Radioactive Waste (HTRW)

Impacts associated with HTRW materials were assumed if HTRW materials were present in the dredging template or disposal areas. The potential presence of HTRW in sediments was a consideration for the in- water disposal sites and was determined by a review of previous dredging experience and by review of the Corps' sediment testing data. The presence of HTRW materials at the upland disposal sites was determined from Phase 1 environmental site assessments that included interviews with the property owners, searches of title records and environmental databases, and field inspections of the proposed disposal sites.

2.3.2.5 Traffic Safety

Impacts associated with traffic safety were evaluated for construction activities and for the transport of dredged material. Potential impacts could occur from the additional traffic on existing roadways and from truck traffic crossing major roadways that would occur under some of the alternatives. Therefore, the development of the conceptual designs for the upland disposal and transfer sites took into account traffic safety. However, a further assessment of safety goes beyond the manageable traffic safety aspects of the project and focuses on the longer term, unavoidable traffic safety issues. Where heavy, industrial-type activities (such as the transfer and handling of large quantities of dredged material) would be located immediately adjacent to major highways and or recreation facilities, the distraction was considered an unavoidable safety impact.

2.3.2.6 Wetlands

Wetlands were identified using spatial data provided through the National Wetlands Inventory (NWI), field reconnaissance, and aerial photo interpretation. The NWI inventory was compiled from aerial photo interpretation and is not inclusive of all wetlands.

The proposed upland disposal and transfer sites and the Snake River shoreline adjacent to Asotin and Asotin Creek were visited to evaluate impacts from the proposed upland storage and levee raise alternatives. Most of the alternatives involved minor indirect effects on wetlands; however, the alternatives that proposed use of a transfer site for handling dredged material were determined to have major impacts on wetlands.

2.3.2.7 Water Quality

The preliminary assessment of water quality impacts of alternatives was based on existing water quality data, previous Corps environmental documentation, and consultation with Corps staff.

The following factors were used in evaluating potential water quality impacts of the alternatives:

• Turbidity is the primary water quality criterion of concern.

• Sediment quality could affect water quality and required consideration.

• Monitoring and mitigation could reduce turbidity impacts to below significant levels.

• Upland disposal and dewatering of dredged material would be unlikely to cause significant water quality impacts.

2.3.2.8 Cultural Resources

The cultural resources assessment is based on review of available literature and the resource files at the Washington Office of Archaeology and Historic Preservation, the Idaho State Historic Preservation Office, and the Walla Walla District Corps of Engineers. Information on cultural resources was gathered for proposed upland and in- water disposal areas and proposed dredging templates. Preliminary evaluations of impacts to cultural resources were based on the presence of identified cultural properties that a given alternative could potentially affect through activities such as dredging and disposal of dredged material.

2.3.2.9 Lower Snake River Fish and Wildlife Compensation Plan (LSRFWCP)

As part of the LSRFWCP, a terrestrial wildlife mitigation program was initiated to:

• Protect existing habitat.

• Provide high-quality upland habitat for a variety of wildlife.

• Obtain additional land to fully compensate for upland game habitat losses that resulted from the construction of the lower Snake River dams.

The plan called for the creation of a number of HMUs to accomplish these goals. The Joso site that was considered for upland disposal of dredged material is managed as an HMU, and the Chief Timothy transfer site is adjacent to an HMU. Use of any of these upland disposal sites would require avoiding adverse impacts to the HMUs, and mitigation of unavoidable adverse impacts. Beneficial uses, such as woody riparian habitat development, would assist in meeting the compensation goals of the plan.

2.3.2.10 Aquatic Impacts on Non-Listed Species

Findings from previous Corps documents, a review of scientific literature, and first- hand knowledge by Corps and University of Idaho biologists were considered to determine the presence or absence of non-listed species. As with the endangered species, an analysis of habitat requirements, presence or absence of fish species, and the timing of migrations were evaluated to determine potential impacts to resident fish. By disposing of materials near shore and building shallow water benches, certain in-water disposal alternatives would provide an opportunity to enhance habitat for resident fish species. In other cases, such as upland disposal, the alternative would not impact aquatic species.

2.3.2.11 Terrestrial Impacts on Non-Listed Species

A Corps terrestrial ecologist determined the potential effects of alternatives on terrestrial wildlife habitat for non- listed species. Proposed upland disposal involving the Chief Timothy and Page Creek sites was determined to have the greatest impact because of the value of the habitat at Page Creek.

2.3.2.12 Regional Economic Impacts

Regional economic impacts are a measure of changes in personal income, sales, or value added expected in the region as a result of each alternative. This criterion considers the impacts from navigation transportation and flood-related activities on employment changes and shifts, and their effects on the regional economy. Each alternative would be expected to provide the same level of navigation benefits and, therefore, no change in that sector of employment or business activity was considered. Each alternative would produce a different flood damage reduction effort and a variety of different effects on jobs.

2.3.2.13 Land Use Impacts

The evaluation of potential land use effects of the alternatives was based primarily on the local property effects and the acquisition requirements of each alternative. The focus of this evaluation was the developed/urbanized areas around Lewiston, Clarkston, and Asotin, but also considered upland disposal impacts. While all levee alternatives would involve impacts to infrastructure and recreation activities, none of the alternatives would cause substantial shifts in land use.

2.3.2.14 Public Perception

Public perception of each of the alternatives was qualitatively assessed based on the DMMS Public Scoping Meeting Summary prepared by the Corps following two regional public meetings held in Richland, Washington, and Lewiston, Idaho, in September 1998. Public comments represented in the Scoping Meeting Summary were general in nature and did not address specific dredging, levee modification, and disposal scenarios considered as part of this preliminary evaluation process. Comments received on the Draft DMMP/EIS were considered and are attached as Appendix O.

2.4 MEASURES REMOVED FROM FURTHER CONSIDERATION

Following preliminary screening, a distinction emerged between those measures that most efficiently met the purpose and need and those measures that had high environmental and economic impacts. Through this screening process, alternatives that were infeasible and/or had potentially high costs and environmental impacts in comparison to other measures could be removed from further consideration.

Table 2-5 summarizes the measures that were removed from further consideration.

The measures that were advanced for further consideration are presented in the following section.

2.5 ALTERNATIVES SELECTED FOR FURTHER CONSIDERATION

Following a process of defining the purpose and need for the programmatic DMMP/EIS and developing a broad range of plan measures, the Corps conducted a screening of those measures, considering environmental, technical, and economic factors. From those measures, alternatives that are reasonable and fulfill the requirements of the purpose and need were formulated. These alternatives are subject to detailed environmental and socioeconomic review (presented in sections 3 and 4 of this DMMP/EIS); from this set of alternatives, a preferred alternative was selected.

This section presents the alternatives that have been formulated from plan measures that passed the screening process and are evaluated in this DMMP/EIS. In addition, this section presents the "No Action" alternative, which provides a baseline for comparison, and is required by NEPA.

For the purposes of this DMMP/EIS, the "No Action" alternative is defined as no change and referred to as the "No Action (No Change)" alternative. The "No Action (No Change)" alternative includes the Corps' anticipated program of continued maintenance dredging in the lower Snake River and McNary reservoirs. This maintenance program includes dredging the navigation channels and other related facilities (ports, moorages, recreation areas, and irrigation intakes), and providing some restoration of flow conveyance at the confluence area of the Lower Granite reservoir. Selection of "No Change" is consistent with the Council on Environmental Quality's guidance in NEPA's Forty Most Asked Questions which states that where ". . . on-going programs initiated under existing legislation or regulations will continue, even as new plans are developed.. 'no action' is 'no change' from current management direction or level of management intensity." (46 Federal Register 18026, as amended, 51 Federal Register 15618). Table 2-6 provides a summary comparison of the alternatives and sections 2.5.1 through 2.5.4 provided detailed descriptions of the alternatives.

2.5.1 Alternative 1 - No Action (No Change) - Maintenance Dredging With In-Water Disposal

2.5.1.1 General Description

This alternative considers those activities (mechanical dredging and in- water disposal) that have been performed in the recent past to maintain the aut horized depths in the navigation channels of the lower Snake River dams and McNary navigation project. The areas covered include Lake Wallula behind McNary on the Columbia River and the reservoirs behind the four lock and dam projects on the lower Snake River: Ice Harbor, Lower Monumental, Little Goose, and Lower Granite. This navigation project provides for a 14-foot (4.3-m) channel with at least 14 feet (4.3 m) over the sills at each of the locks and 14-foot (4.3-m) by 250-foot (76.2-m) channels providing access to port and barge loading facilities in each reservoir. Sediment has been deposited over time, reducing the navigation clearances in places in each reservoir and the flow conveyance capacity of the upper reservoir behind Lower Granite. This alternative would provide navigation clearance and provide some restoration of the flow conveyance capacity based upon maintenance dredging.

Additionally, maintenance dredging of access channels to ports and moorages occurs infrequently, on an as-needed basis. The Corps also periodically conducts maintenance dredging around public recreation areas, such as swimming beaches and boat basins, and irrigation intakes for wildlife HMU's managed by the Corps.

2.5.1.2 Dredging Areas and Quantities

Maintenance dredging is a project component to maintain navigation clearances in each of the five reservoirs and maintain flow conveyance of the Lower Granite reservoir. Dredging templates were designed for each reservoir to achieve the maintenance dredging requirements. For the Lower Granite reservoir, the areas that require dredging for navigation are located on the Clearwater River between the Snake River confluence and the Port of Lewiston, located between Clearwater RM's 0.00 and 1.56, and on the Snake River from the vicinity of Silcott Island near Snake RM 131 upstream to the U.S. Highway 12 bridge located near Snake RM 139.5. A range of dredging volumes between 16,000 and 300,000 cy (12 232.9 and 229 367 m³) are required on a 2-year cycle to develop and maintain the designed navigation channels in the Lower Granite reservoir. An estimated 4,000 cy (3 058 m³) are to be dredged from behind Little Goose, and 2,000 cy (1 529 m³) from behind Lower Monumental and Ice Harbor dams at 2- year intervals. The areas to be dredged in each case are located at the upstream end of each reservoir. The maintenance dredging for the McNary reservoir is estimated to be approximately 32,000 cy (24 466 m³) every 2 years. The maintenance dredging and disposal areas for each of the five reservoirs are identified on the plates.

2.5.1.3 Dredging Template Design

The navigation dredging template is 250 feet (76.2 m) wide, with dredging to provide a channel depth of 14 feet (4.3 m) below the minimum authorized pool elevation of 733 feet msl at Lower Granite, 633 feet msl at Little Goose, 537 feet msl at Lower Monumental, 437 feet msl at Ice Harbor, and 335 feet msl at McNary. The dredging template for other maintenance activities would vary, but includes access to port and moorage facilities, public recreation areas, and irrigation intakes.

2.5.1.4 Dredging Program and Process

Dredging would be accomplished mechanically, probably using a clamshell with an approximate 15-cy (11.5-m³) capacity discharging to a barge with a capacity of 3,000 cy (2 293.7 m³). The barges would have a maximum size of 240 feet (73.2 m) long by 42 feet (12.8 m) wide with a maximum draft of 14 feet (4.3 m). The expected rate of dredging is 5,000 cy (3 822.8 m³) per 8-hour shift. Dredging would be performed in the Snake River during the period of December 15 through March 1 and for a longer period from December 1 to March 31 in the Columbia River. Multiple shift dredging workdays would be used when necessary to ensure that dredging was completed within these windows.

All material dredged in the Lower Granite reservoir would be disposed of downstream of Centennial Island, located near Snake RM 120.46. The entire channel below elevation 670 feet msl is available to be used for material disposal as required. Sands, gravels, and cobbles, expected to comprise 85 percent of the total material, would be dumped in the shallow to mid-range depths from 15 to 60 feet (4.6 to 18.3 m) to form shallow water habitat. Approximately 15,000 cy (11 468.3 m³) of dredged material would be deposited per acre. The remaining 15 percent of material that is silt or finer would be deposited in deep water. This alternative would use only a small portion of the total volume of dredged material available for deposition. The total disposal volume available for the entire disposal area based on a level horizontal surface at elevation 670 feet msl was computed from a 1997 survey as approximately 120 million cy (91 746 600 m³).

The 4,000 cy (3 058 m³) of dredged material originating from behind Little Goose reservoir and 2,000 cy (1 529 m³) of material from Lower Monumental and Ice Harbor reservoirs at 2-year intervals would be disposed of at in- water sites immediately upstream of the respective dams. The 32,000 cy (24 466 m³) of material removed from the McNary reservoir at 2-year intervals would be disposed of at in-water sites near the confluence of the Columbia and Snake Rivers to form improved fish habitat and in deep-water sites downstream of the Walla Walla River (plates 3 and 4).

2.5.1.5 Material Types

Dredged materials would be comprised mostly of sediments containing a mixture of silts, sands, gravels, and cobbles carried by inflowing waters as suspended and bedload material. Based on previous experience, 85 percent of the material is expected to be sands, gravels, and cobbles, and 15 percent of the material is expected to be silts and finer-grained material. Small amounts of material unsuitable for in-water disposal may require disposal at an upland site.

2.5.2 Alternative 2 - Maintenance Dredging With In-Water Disposal to Create Fish Habitat

2.5.2.1 General Description

This alternative considers the same dredging activities as alternative 1, "Maintenance Dredging" or "No Action (No Change)," but with changes in dredging methods, work window, and disposal location for silt. Mechanical dredging would still be the primary dredging method used, but hydraulic dredging would also be considered for off-channel areas on a case-by-case basis. The majority of the dredging would be done during the winter in-water work windows used in the "No Action (No Change)" alternative, but a summer work window, possibly August, would be considered for off-channel areas on a case-by-case basis. All summer dredging would use upland disposal of the dredged material. The disposal method for winter dredging is formalized to include in-water disposal of most of the dredged material to create shallow water fish habitat. Silt would no longer be disposed of in deep-water sites. The areas dredged for channel maintenance remain the same and include Lake Wallula behind McNary on the Columbia River and the reservoirs behind Ice Harbor, Lower Monumental, Little Goose, and Lower Granite on the lower Snake River. Additionally, maintenance dredging of access channels to ports and moorages occurs infrequently, on an as-needed basis. The Corps would continue to periodically conduct maintenance dredging around public recreation areas, such as swimming beaches and boat basins, and irrigation intakes for wildlife HMU's managed by the Corps.

The disposal sites for this alternative would likely differ from alternative 1. The Corps evaluated all five reservoirs for potential sites suitable for in-water disposal. Sites were restricted to areas in the lower ends of each reservoir to eliminate the potential to negatively affect water surface levels at the upper end of each reservoir. For several reasons, the Corps concentrated its evaluation of sites on Lower Granite reservoir. One is that it is the uppermost reservoir and juvenile salmonids found in that reservoir would benefit more from additional rearing areas and associated increased growth potential. Another reason is that there are no collection and transport facilities above Lower Granite; therefore, more juveniles use Lower Granite reservoir than the other reservoirs. Finally, most of the dredging would occur in Lower Granite reservoir; therefore, it would be more cost-effective to dispose of the material within the reservoir. However, in-water disposal to create shallow-water habitat in other reservoirs would be considered depending upon the location of the dredging area, the type of material to be dredged, and the quantity to be dredged.

The Corps identified seven potential sites in Lower Granite reservoir suitable for shallow water rearing habitat creation (figure 2-6). The sites were identified because they are on the inside of a river bend, have suitable water velocities and underwater contours to facilitate habitat creation, and they are configured so the dredged material can be deposited without burying known cultural resource sites.

 

Alternative 2 would employ an "adaptive management" approach to the overall implementation of the DMMP. The Local Sediment Management Group (LSMG) (see Section 1.8) would provide input and feedback to the Corps with respect to dredging and dredged material management that would be implemented under this alternative, as well as Alternatives 3 and 4.

The adaptive management approach would allow the Corps and the LSMG to regularly evaluate dredging and dredged material management activities and monitoring results, and make needed adjustments to the overall course of action.

A levee raise of up to 3 feet (0.9 m) at critical locations is added to this alternative to maintain the flow conveyance capacity of the upper reservoir behind Lower Granite at the confluence of the Snake and Clearwater Rivers.

2.5.2.2 Disposal Process

The disposal process is dependent on the physical characteristics of the material and the potential to optimize the benefit to fish. Sediment samples would be taken from the areas to be dredged and would be evaluated for particle size, contaminant levels, and suitability for in- water disposal. Particle size analysis would identify which dredging sites or portions of sites contain mostly silt and which ones contain mostly sand or coarser material.

The sequence of dredged material disposal for the majority of the dredging activities is designed to accomplish two goals: (1) create shallow-water habitat for juvenile salmon, and (2) dispose of silt in a beneficial manner. To meet these goals, the dredged material would be placed in steps. The first step would be to use the silt [less than .008 inch (0.2 mm) in diameter] in a mixture with sand and gravel/cobble to fill the mid-depth portion of a site and form a base embankment. The dredged material would be placed aboard bottom-dump barges and analyzed to determine the percentage sand or silt to ensure the mixture in the embankment was not more than 30 percent silt. The barges would then proceed to the disposal area and would dump the material within the designated footprint close to the shoreline to raise the river bottom to create an underwater shelf about 10 feet (3 m) below the desired final grade. The second step would be to place sand on top of the sand/silt embankment. An area of sand would be reserved as the final area to be dredged during that dredging activity. Barges would be used to dump the sand on top of the base embankment in sufficient quantity to ensure that a layer of sand at least 10 feet (3 m) thick covers the embankment once the final step of the process is completed. The footprint of the disposal area would be sized so that the maximum amount of shallow water habitat is created with the estimated quantities of material to be dredged during that dredging activity. The final step would be to use a beam drag to flatten and level the tops of the mounds to form a flat, gently sloping (3 to 5 percent) shallow area with water depths up to 20 feet (6.1 m) as measured at minimum operating pool level. The sand cap layer would be created with a minimum thickness of 10 feet (3 m) to ensure the most desirable substrate (sandy with limited fine- grained or silt material) is provided for salmonid rearing habitat.

To determine the minimum surface acreage of habitats to be created, pre-impoundment aerial photos of the shorelines of the lower Snake River were studied and the sandy, shallow water areas conducive to rearing fall chinook were measured. Historically, a wide size range of these habitats existed but a minimum surface area for shallow water habitat creation was designated as 4 acres (1.6 hectares). This acreage was actually lower than the average habitat area found pre-impoundment but was calculated as the minimum necessary to attempt to mimic the free-flowing shoreline habitat required by fall chinook salmon.

On a case-by-case basis, hydraulic dredging may be considered for off- channel areas such as irrigation intakes. This would probably be done in the summer when salmonid fish are less likely to be found in these shallow water areas because of elevated water temperatures. To minimize turbidity, the hydraulic dredging would be limited to methods that do not agitate the sediments. The dredged material would exit the dredge as a slurry that is likely to be 65 to 80 percent water and would not be suitable for in-water disposal as described above. Instead, this slurry could be incorporated into the wildlife habitat planting areas or used to restore eroded streambanks near the intakes.

Summer dredging may also be considered for other off-channel areas such as swim beaches or boat basins on a case-by-case basis. These shallow-water areas wo uld be expected to have elevated water temperatures during the summer and would not likely have salmonid fish present. The material dredged from these sites would probably be disposed of at an upland location since the in-water disposal areas are located in the main river channel and may have salmonid fish present during the disposal activity.

Table 2-7 compares the dredging options of timing, method, and disposal location for the various areas that would be dredged under this DMMP/EIS.

A contingency upland disposal site has been identified to provide storage for dredged material that may, for whatever reason, need to be deposited on a separate upland site. In the event that dredged material may be unsuitable for beneficial use or disposal in- water, it would be isolated at the Joso upland disposal site (RM 56.5 and RM 58.6) and appropriate confinement measures would be taken to isolate this material (e.g., installing an impervious liner to prevent leaching of contaminated materials).

2.5.2.3 Levee Raise

Sediment accumulation in the Lower Granite reservoir continues to reduce the level of protection provided by the levees at Lewiston, Idaho. The proposed levee raise would result in the following:

Levees: The west Lewiston levee would be raised as much as 3 feet (0.9 m) in some locations. However, on the whole, most levee raises would be less than 3 feet (0.9 m).

Highways/Roads: Highway 129 downstream of Asotin and the Snake River Road upstream of Asotin would be raised.

Recreation Areas: The plan calls for cleanup of Hellsgate State Park, Swallows Park, and the Corps Clarkston office, boat ramp, and restrooms in the event of a flood.

Commercial Buildings: The plan would increase in the risk of flooding one commercial building, a U.S. Forest Service building, and a Corps building. The levee raise would not affect utilities, bridges, railroad tracks, or private homes.

2.5.3 Alternative 3 - Maintenance Dredging With Upland Disposal and a 3-Foot (0.9-m) Levee Raise

2.5.3.1 General Description

This alternative considers the same dredging activities as alternatives 1 and 2, but with upland disposal of all dredged material and no in-water disposal. The 3-foot (0.9- m) levee raise described as a part of alternative 2 would be included with this alternative (see section 2.5.2.3). The areas dredged for channel maintenance in this alternative remain the same and include Lake Wallula behind McNary on the Columbia River and the reservoirs behind Ice Harbor, Lower Monumental, Little Goose, and Lower Granite on the lower Snake River. This alternative would continue to maintain the navigation clearances in each reservoir and maintain the flow conveyance capacity of the upper reservoir behind Lower Granite. Additionally, maintenance dredging of access channels to ports and moorages occurs infrequently, on an as- needed basis. The Corps would continue to periodically conduct maintenance dredging around public recreation areas, such as swimming beaches and boat basins, and irrigation intakes for wildlife HMU's managed by the Corps. This alternative would ensure navigation clearance and maintain the flow conveyance by raising levees that protect Lewiston, Idaho, as in alternative 2. Under this alternative, dredged materials would be transported by barge to the Joso upland disposal site.

2.5.3.2 Upland Disposal Site

The location for upland disposal of dredged material would be the Joso site on the Snake River below Little Goose on the sout h bank at RM 56.5 to RM 58.6 (plate 11). The site is located at a bend in the river and is bounded on the southern side by the Union Pacific Railroad, giving it a roughly triangular shape. The entire site is approximately 568 acres (229.9 hectares), with open space/habitat management being the present use. Barge access to the Joso site would be at the west end providing access to a disposal area of approximately 280 acres (113.3 hectares) located in the center of the site with 600-foot (182.9-m) buffers from the river. Initially, the disposal area would be confined to a disturbed site that was historically used for gravel extraction and currently contains an exposed open gravel pit.

Use of the Joso site would require reconstruction of some facilities and construction of others. The existing barge slip would need to be dredged to restore access. The barge slip would also be reconstructed using anchored sheet pile to provide vertical walls and tie off facilities. Temporary dredged material dewatering and storage areas with containment berms and detention ponds would be constructed adjacent to the slip. The material would be off-loaded from the barges and placed in the temporary storage for dewatering, then would be loaded onto trucks for transport to the disposal area. The material would then be placed in lifts using track-type tractors and compacted, resulting in a large structural fill conforming to the established final topography for the disposal area. Areas that reach final grades would be restored on a periodic basis by placing 6 inches (15.2 cm) of topsoil and re-seeding with native grasses to achieve a vegetative cover similar to the surrounding site areas. Filling the gravel pit with sediment and seeding it to grass would improve the site's va lue as wildlife habitat. Contaminated or unsuitable dredged materials would be isolated and appropriate confinement measures taken (e.g., an impervious liner installed to prevent leaching).

2.5.4 Alternative 4 - Maintenance Dredging With Beneficial Use of Dredged Material and

2.5.4.1 General Description

This alternative considers the same dredging activities as alternatives 1, 2, and 3 with mechanical dredging as the primary dredging method. Hydraulic dredging would be considered on a case-by-case basis for off-channel irrigation intakes only. The areas dredged for channel maintenance remain the same and include Lake Wallula behind McNary on the Columbia River and the reservoirs behind Ice Harbor, Lower Monumental, Little Goose, and Lower Granite on the lower Snake River. Additionally, maintenance dredging of access channels to ports and moorages occurs infrequently, on an as- needed basis. The Corps would continue to periodically conduct maintenance dredging around public recreation areas, such as swimming beaches and boat basins, and irrigation intakes for wildlife HMUs and recreation sites managed by the Corps.

As with alternatives 2 and 3, a levee raise of up to 3 feet (0.9 m) at critical locations is added to this alternative to maintain the flow conveyance capacity of the upper reservoir behind Lower Granite at the confluence of the Snake and Clearwater Rivers (see 2.5.2.3).

2.5.4.2 Beneficial Uses

The management strategy for dredged material under this alternative would be beneficial use. Beneficial uses could include creation of shallow-water fish habitat, creation of riparian habitat, fill material for construction, etc. For each dredging activity, the Corps would identify potential beneficial uses and coordinate the uses with the LSMG prior to selecting a use. Beneficial uses, as defined by this process, may be achieved when a local sponsor is willing to contribute a share of the cost. Potential beneficial uses that have been identified to date include:

2.5.4.2.1 Fish Habitat Creation

Fish habitat creation would be the same disposal method used in alternative 2, "Maintenance Dredging With Beneficial In-Water Disposal and a 3-Foot (0.9-m) Levee Raise." This method is described in section 2.5.2.2. This beneficial use would result in the creation of shallow-water fish habitat to benefit juvenile salmonid fish.

2.5.4.2.2 Woody Riparian Habitat Program

The Corps has proposed the "woody riparian" program to help meet the goals of the Lower Snake River Fish and Wildlife Compensation Plan within the state of Washington. The woody riparian program would create and enhance riparian habitats along the lower Snake River.

The Lower Snake River Fish and Wildlife Compensation Plan (LSRFWCP) was drafted in 1975 to provide direction and funding for environmental mitigation as a result of the construction of lower Snake River lock and dam projects. The LSRFWCP was divided into components to address anadromous fish, resident fish, and terrestrial wildlife. The woody riparian program has been developed to address the LSRFWCP's specific goals for terrestrial wildlife mitigation.

Initially, the Corps proposes to implement the woody riparian program in Lower Granite Reservoir near the Chief Timothy Habitat Management Unit. Proposed woody riparian habitat creation would consist of developing a shallow, sloping bench (approximately two feet below surface at the maximum operating pool), extending along approximately 3,000 linear feet of shoreline between RM 131.6 and 133.4. The Corps has identified this particular site because it has a high potential for successful woody riparian habitat development, would not interfere with navigation, would not impact known cultural resources, and would be close to the Snake/Clearwater River confluence where most dredging is proposed to occur. Dredged material placed in this proposed area would accomplish three goals consistent with the LSRFWCP:

• Create planting zones for woody riparian habitat;
• Increase suitability and acreage of shallow water rearing habitat for Snake River fall chinook juveniles; and
• Provide a beneficial use of dredged material.

The Corps proposes to use dredged material from planned 2002-2003 dredging to develop woody riparian areas as described above. Details of proposed woody riparian habitat development are provided in Appendix N.

2.5.4.2.3 Hanford Site Capping

The Richland Office of the U.S. Department of Energy (USDOE) has responsibility for management of the nearby Hanford site (plate 7). The 570-square-mile (1 476.3-square-km) Hanford Site was founded early in World War II to produce plutonium for the nation's first atomic weapons. Since the mid-1950's, the mission of Hanford has broadened to meet energy and defense needs. One of the many uses of the Hanford site has been the storage of contaminated wastes including commercial, low- level radioactive waste received from hospitals, research facilities, industries, and nuclear power stations. Treatment and storage of these contaminated wastes often involves the use of clean soils as a capping material. While the quantities of material required for capping of burial sites on the Hanford site have yet to be determined, Comprehensive Environmental Response Compensation Liability Act (CERCLA) of 1980 and Resource Conservation and Recovery Act (RCRA) compliance indicates that there could be requirements for large volumes of materials including: fine-grained clays and silts, fine to coarse gravel, cobbles, and larger stone or riprap material. The quality of materia ls imported onto the Hanford site is of concern and all such materials must be sampled to identify constituents and/or contaminants. The USDOE is in the process of evaluating sources of fill for uses on the Hanford site. The USDOE will be addressing issues such as availability of off-site materials, the impact of utilizing on-site borrow material, site restoration requirements, and the anticipated volume of materials required in the near future (USDOE, 1999).

Dredged material would provide an excellent source of clean material for this use. Dredged material from channel maintenance dredging in McNary reservoir (Lake Wallula) could be used by barging these materials an additional 10 miles (16.1 km) and off- loading them at facilities owned by the Port of Benton adjacent to the Hanford site. Costs for this beneficial use would be determined by the added cost to transport the material to the off-load and temporary storage facilities. The added maintenance dredging costs for this additional 10 miles (16.1 km) of barge transport and off- loading would be borne by the USDOE. Storage at the temporary site and transportation of the material to the use location would be the responsibility of the USDOE.

2.5.4.2.4 Potting Soil

Dredged material removed from the Lo wer Granite reservoir has constituents that make it excellent as a potting soil or soil enhancer. The Port of Whitman County has investigated a system that processes straw, digestible solid waste, and soil (dredged material as proposed in this alternative) in a continuous digester to produce a final product that is used as potting soil, top dressing for turf areas such as golf courses and parks, or to enhance production of agricultural crops. Straw, a surplus commodity from the highly productive Palouse Hills grain growing area adjacent to the Port of Wilma, is an ideal raw material for this process. Solid waste from the Lewiston-Clarkston-Pullman-Moscow metropolitan areas can be classified to remove recyclable materials and other unsuitable materials that might make it unusable as a raw material for this digestive process. Dredged materials from Lower Granite reservoir would supply the third raw material for this process. The net result would be to convert straw, solid waste, and dredged materials into a marketable commodity. This would create a new industry for this region of Washington and Idaho with resultant gains in employment and spendable income. The Port of Whitman County has proposed packaging this material for sale in the region. Their plans call for up to 300,000 cy (229 367 m³) per year of dredged material to be delivered by barge to a temporary holding site at the Port of Wilma. The additional cost of this activity would be paid by the Port of Whitman County.

2.5.4.2.5 Riparian Habitat Restoration

Dredged material has been used to construct riparian habitat in this reach of the Columbia/Snake River system, similar to that described in section 2.5.4.2.2 above. Where additional opportunities exist to barge and off- load material to cover riprap, to create islands or to build sub-impoundment areas, local sponsors may contract with the Corps to construct these projects on a one-time basis. The added cost of dredging maintenance required to use the dredged material to restore the environment would be cost-shared 25 percent by a local sponsor and 75 percent by the Federal government. Section 204 of the Water Resources Development Act of 1992 provides the authority for this cost sharing, provided that the local sponsor provides all lands, easements, rights-of-way, and relocations necessary, and owns and operates the finished project. The following projects and sponsors were tentatively identified as potential beneficial uses of dredged material to restore the ecosystems on existing levees:

• Levee 2C - City of Richland: Create shallow shoreline areas by filling over existing steep slopes.

• Levee 4A - City of Richland: Create shallow backwater near the Yakima River confluence.

• Levee 12-1 - City of Pasco: Fill at the toe of the existing levee creating a gentle shelf to 15-foot (4.6-m) water depth.

• Levee 12-2 - Franklin County: Create a gently sloping shallow-water area to 15 feet (4.6 m) deep.

• Levee 5D - City of Kennewick: Fill from Clover Island to Blue Bridge at a slope of 7 feet horizontal to 1 foot vertical (7:1).

• Clover Island - Port of Kennewick: Fill from east end of the island to the Cable Bridge at a slope of 7:1 and fill from the west end of the island to create a flat shallow extending to a berm angling at 30 degrees from the levee.

• Levee 6B - Benton County: Fill along the shore downstream of the Cable Bridge to produce flat shallows.

• East of Two Rivers Park and Levee 15D - Benton County: Fill near shore areas to create flat shallow fish habitat.

2.5.4.2.6 Port of Wilma Fill

The Port of Wilma has long-term plans to fill the empty dredged material disposal cells previously formed west of and adjacent to the currently developed port facilities. This potential dredged material disposal area currently has the capacity to accommodate approximately 370,000 cy (282 885.3 m 3 ) of dredged materials in Cell #2 and 100,000 cy (76 455.5 m³) in Cell #3. Access to this site for future disposal of dredged materials is currently hampered by near-shore shallow waters designated as critical habitat for listed juvenile fall chinook salmon and potential cultural resource impacts.

Access for unloading of dredged materials appears to be available at two locations adjacent to these potential dredged material disposal sites. Barge access is currently available at the west end of the developed area at the Port of Wilma (e.g., land leased by Tidewater Barge Lines for the purpose of constructing and launching barges). It may be possible to off- load dredged material from barges at this site and to stockpile these dredged materials on site. These stockpiled dredged materials could then be transferred across a previously filled and currently undeveloped dredged material disposal cell to currently available dredged fill disposal areas. These materials could be transferred hydraulically using pumps and pipelines or mechanically by using earthmoving equipment.

A second potential site for off- loading dredged material from barges exists approximately 3,000 feet (914.4 m) downstream from the west end of the Port of Wilma developed area. This is an area, offshore from the potential disposal area, approximately 700 feet (213.4 m) long by 150 feet (45.7 m) wide that is filled to an elevation of 740 feet msl. This appears to be downstream of juvenile salmonid habitat areas and appears to have sufficient water depth adjacent to the riverside face to accommodate loaded barges. Dredged material could be moved via a causeway some 500 to 600 feet (152.4 to 182.9 m) shoreward to the disposal area by conveyor or earthmovers for placement in the potential disposal area.

The increased cost of transport and off-load of the dredged material would be borne by the Port of Wilma.

2.5.4.2.7 Fill of Non-Federal Public Land

Non-Federal requests for beneficial use of dredged material to fill land may be allowed, provided additional implementation costs are non-Federal and no additional cost would accrue to the Federal project. The non-Federal cost share shall be the difference between the base plan presented in this document and the cost of delivering the dredged material to meet the non-Federal sponsor's beneficial use.

2.5.4.2.8 Lower Granite State Route (SR) 193/SR 194 Road Connection

The Port of Whitman County has promoted the construction of a section of roadway along the north shore of the Lower Granite reservoir linking SR 193 at Wawawai to SR 194 at Lower Granite. A new 3-mile (4.8-km) section of roadway at this location would eliminate use of a 32-mile (51.5-km) stretch of steep, narrow roadway via SR 193 and SR 194 to access Lower Granite from the Port of Whitman County's Port of Wilma facility near Lewiston and Clarkston. The proposal is to use dredged material to construct a structural berm in Lower Granite reservoir on which this 3.5-mile (5.6-km) roadway would be constructed. This berm would be constructed in conjunction with placement of additional dredged materials between the shoreline and the structural berm to create a shallow-water habitat, along the north shore of this deeper part of Lower Granite reservoir, to facilitate downstream migration of juvenile salmon and steelhead. A Feasibility Study entitled "Construction of Road from Lower Granite to Wawawai Canyon, Whitman County, Washington," dated September 1981, prepared by the Walla Walla District, U.S. Army Corps of Engineers presented nine alternative routes for construction of this road.

There are numerous benefits associated with this alternative. The Whitman County Sheriff's Department has documented that construction of this 3.5-mile (5.6-km) road segment would eliminate the current 45-mile (72.4-km) drive from Wawawai to Boyer Park near Lower Granite. They cite emergency response times, icy winter driving conditions and heavy usage of both Wawawai and Boyer Parks by university students as safety issues that justify the construction of this road segment. Recreational benefits, presented by the Whitman County Parks and Recreation Department, include increased recreational usage of both Boyer Park and Wawawai Park; increased access to the Snake River (Lower Granite reservoir); and completion of recreational facilities for the Lower Granite project. The economic benefits are related to movement of bulk commodities, mostly grain, by truck from the Lewiston-Clarkston area and from grain growing areas closer to Almota. Travel distance from the Lewiston-Clarkston area to government-owned and -operated facilities at Lower Granite would also be reduced.

Examination of preliminary roadway sections developed during the 1981 Corps study indicates that significant quantities of dredged materials could be incorporated into construction for one of the proposed routes. The initial route involves construction of this roadway upon fill placed adjacent to and on the riverward side of the existing railroad tracks. It is estimated that this route could accommodate 500,000 cy (382 277.4 m³) of dredged materials. The Corps estimated the total cost of constructing this route at $14.8 million in 1981. Allowing a 30 percent cost escalation for inflation, the present day construction cost for this route would be approximately $20 million.

The 1981 Corps study had identified the least expensive route as constructing a roadway on the landward side of the railroad tracks and involved mostly excavation into the steep terrain adjacent to the railroad. The estimated costs for the least expensive route were estimated at $6.71 million in 1981. The Corps identified another route as the preferred route. This route was generally constructed on the landward side of and parallel to the existing railroad tracks; however, it involved three railroad crossings and approximately 6,000 feet (1 828.8 m) of roadway in or adjacent to Lower Granite reservoir. It is estimated that this route could accommodate approximately 200,000 cy (152 911 m³) of dredged materials. In 1981, the Corps estimated construction costs for the preferred route at $7.87 million. Allowing a 30 percent cost escalation for inflation, the present day cost would be approximately $10.25 million.

Comparing the beneficial use for these two roadway routes to the proposed in-water dredged materials disposal alternative results in an additional cost for disposal. Construction of the various routes considered would utilize some 500,000 cy (382 277.4 m³) of dredged materials. Construction of the preferred route would utilize some 200,000 cy (152 911 m³).

Utilization of dredged materials is subject to determining a satisfactory means of placing the dredged materials, the structural suitability of these dredged materials, and environmental considerations. Use of dredged materials for roadway embankment could significantly reduce the overall cost of construction for either the initial route or the preferred route as proposed by the Corps in the 1981 study.

2.5.4.2.9 Research of Beneficial Uses

Two research groups at the Corps of Engineers Waterways Experiment Station (WES) in Vicksburg, Mississippi, are investigating measures to use this type of material. One group may be interested in determining economic and biological values to be obtained from the use of the material in the riparian environment. The other group may be interested in demonstrating the application of this material as a top dressing composed of sewage sludge, dredged material, and other ingredients. Dredged material removed from the Port of Walla Walla barge channel at Boise Cascade is expected to be predominantly fine grain sediment suitable for use as a top dressing and habitat restoration. There are various locations within proximity to the Boise Cascade channel that provide the opportunity including sites in The Dalles reservoir (The Cliffs), John Day reservoir (Goodnoe, Plymouth), and McNary reservoir (Hood Park and the various Shot Rock Islands). The LSMG may look for opportunities to participate with the WES research groups to implement these research efforts.

2.6 MITIGATION

The environmental effects of the alternatives are discussed in detail in section 4. In general, none of the alternatives under consideration are expected to result in significant environmental impacts. Mitigation strategies have been developed to address the environmental impacts that are expected to result from the alternatives. These strategies are also discussed in section 4.

A prominent programmatic mitigation measure that is relevant to dredging and disposal of dredged material is the creation of woody riparian habitat and shallow-water habitat with the dredged material. Implementation of this mitigation measure would compensate for effects of dredging and disposal activities on aquatic resources, and in particular, endangered salmonid species. The Corps would conduct long-term monitoring of shallow-water disposal sites to evaluate the success and quality of habitat creation.

Mitigation is also proposed for direct and indirect impacts due to dredging, disposal (both upland and in-water), and construction activities related to proposed levee height modifications. In general, mitigation strategies include:

• Avoiding impacts through timing of specific activities or location of upland disposal facilities and construction activities.

• Sampling and analyzing sediments prior to dredging following criteria in the Dredged Material Evaluation Framework.

• Monitoring water quality during dredging and disposal activities to ensure impacts are identified and actions are modified as necessary.

• Minimizing impacts through techniques such as erosion and sedimentation control and other construction best management practices to minimize soil loss, compaction, fugitive dust, and runoff to sur face waters.

• Documenting affected cultural resources and incorporating appropriate mitigation measures.

Other programs provide mitigation for impacts attributed to dam construction and operation. In the case of the four Snake River dams, the Lower Snake River Fish and Wildlife Compensation Plan (Corps, 1983), a congressionally authorized program, provides fish and wildlife mitigation for the impacts caused by the construction and operation of the four dams and reservoirs. The proposed woody riparian program would further the goals of this particular mitigation plan. Mitigation for salmonid fishery impacts includes construction and operation of several fish hatcheries and their satellite facilities to provide salmon and steelhead for commercial and sport fishermen. Mitigation for wildlife impacts includes maintenance of irrigated and non- irrigated HMU's on Corps-owned land adjacent to the lower Snake River. It also includes the purchase and development of additional lands in the lower Snake River basin suitable for wildlife habitat development.

Other Federal laws contain provisions to protect and mitigate impacts to the aquatic environment. The Corps conducts a Clean Water Action Section 404(b)(1) evaluation, which includes evaluating alternatives that do not impact or have a lesser impact on aquatic environment. The evaluation also includes an analysis of the unavoidable adverse impacts and ways to minimize those impacts. The Corps prepared a 404(b)(1) evaluation for the DMMP/EIS and it is included as Appendix I. This appendix is being coordinated with state agencies.

The ESA compliance process will also identify ways to reduce or avoid impacts to listed species and their habitat. In their Biological Opinion for the DMMP, NMFS identified reasonable and prudent measures that would minimize the impacts to listed anadromous fish species and their habitat. In their response document, the USFWS provided similar recommendations for listed terrestrial and non-anadromous fish species. See Appendix F and G for details.

2.7 EVALUATION/SELECTION OF PLAN

The Corps evaluated each of the plans identified previously as "selected for further consideration" based on the following criteria:

• Will the plan maintain the navigation channels of the system?

• Will the plan provide optimal use of material dredged from the reservoirs?

• Will the plan maintain sufficient flow capacity through the Lewiston levee system?

• Does the plan maximize environmental benefits/minimize environmental impacts?

• Does the plan have a favorable cost/benefit ratio?

• Does the plan allow for adaptive management through the 20-year period of the DMMP?

• Does the plan complement regional ESA habitat goals?

• Is the plan regionally acceptable?

• Does the plan address comments identified through the public review process?

The sensitivity of plan measures to variable parameters is discussed in appendix C, Economic Analysis. As also discussed in appendix C, the risk and uncertainty of plan measures were evaluated through the use of the Corps' Hydrologic Engineering Center Flood Damage Assessment model that performs a risk-based analysis of flood control alternatives.

The environmental effects of the four alternatives are discussed in section 4. When preparing the effects analysis, the Corps considered unavoidable effects, short-term uses, long-term productivity, and irreversible or irretrievable commitments of resources. The Corps also considered direct, indirect, and cumulative effects. Table 2-8 summarizes the environmental effects of each of the four alternatives. More detailed discussions of environmental effects are found in select appendices. Appendices F and G contain the Biological Assessments that evaluated the effects of the preferred alternative on plant and animal species listed under the ESA. Appendix K provides a detailed analysis of the effects of the alternatives on aquatic organisms.

Table 2-9 presents a matrix comparing the four alternatives' performance in the areas of the criteria listed above.

Based on the current best available information as summarized in table 2-9, the Corps determined that alternative 4 best met the Corps' needs while minimizing negative environmental impacts and/or maximizing environmental benefits. Therefore, the Corps selected alternative 4 as the preferred alternative for the DMMP. As a result of the initial screening and the final evaluation of alternatives, the Corps also determined that alternative 4 is the environmentally preferred alternative. Appendix O displays the comment letters received on the Draft DMMP/EIS and the Corps' responses to those comments.

2.8 RECOMMENDED PLAN/PREFERRED ALTERNATIVE

The Corps' preferred alternative or recommended plan for long-term management of dredged material is "Alternative 4 - Maintenance Dredging With Beneficial Use of Dredged Material and a 3-Foot (0.9-m) Levee Raise." Alternative 4 is the preferred plan to meet the need to maintain the navigation channels of the system, manage dredged material from the reservoirs, and maintain flow conveyance capacity in the Lower Granite reservoir. Alternative 4 most completely and efficiently meets the project purpose and need at the least cost, while presenting potential environmental impacts that are no greater, and often less, than other alternatives considered. Further, the plan incorporates mitigation features that would restore valuable aquatic and terrestrial habitat to the system. The plan represents the greatest beneficial use of dredged material that can be implemented on a programmatic basis at this time. Furthermore, the plan incorporates an adaptive management approach that provides for on-going evaluation of proposed dredging and dredged material management activities and opportunities to adapt and adjust actions based on these evaluations. The plan becomes the base for cost sharing of other beneficial uses of dredged material that may be identified in the future as each separate dredging activity is planned and executed. Beneficial uses of dredged material may be adopted on a case-by-case basis under this plan as opportunities become available and when local sponsors agree to fulfill sponsorship requirements. To ensure that the plan continues to optimize the use of dredged material, the Corps will coordinate potential beneficial uses for each dredging activity with the LSMG prior to the start of dredging.

The 3- foot (0.9- m) levee raise feature is the preferred plan for maintaining the flow conveyance capacity in the Snake and Clearwater Rivers confluence area of Lower Granite reservoir because it meets the purpose and need and produces maximum net benefits in excess of costs. Raising the levee was found to reduce the need for dredging in the confluence area of Lower Granite reservoir and, therefore, is considered as a part of this DMMP/EIS. Selection of the levee raise as the preferred conveyance restoration method was based on the maximization of net benefits determined from a risk-based flood damage assessment and annual costs amortized over the remaining 74 years of the project life. Since the original Lower Granite slackwater levee system required no local cost sharing, this levee modification at a cost of $2.3 million is recommended to be 100 percent Federal cost.

The following sections provide detailed descriptions of the components of the recommended plan.

2.8.1 Dredging Activity

The dredging procedure to be used varies depending on the location of the dredging. For the dredging proposed for the navigation channels, slips, and berths of the Columbia/Snake/Clearwater Rivers navigation system, mechanical dredging would be used. Mechanical dredging methods would include clamshell, dragline, backhoe, or shovel/scoop. Based on previous dredging activities, the clamshell method would probably be used for the larger quantities. Material would be scooped from the river bottom and loaded onto a bottom-dump barge for in-water disposal or a bin-type barge fo r upland disposal. The contractor would be allowed to overspill excess water from the barge while the barge is being loaded. The water would be discharged a minimum of 2 feet (0.6 m) below the river surface. Clamshell dredges of approximately 15-cy (11.5-m³) capacity and barges with a capacity of up to 3,000 cy (2 293.7 m³) with maximum drafts of 14 feet (4.3 m) would be used. The Corps estimates it could take about 6 to 8 hours to fill a barge. The expected rate of dredging is 3,000 to 5,000 cy (2 293.7 to 3 822.8 m³) per 8-hour shift. The barge would then be pushed by a tug to the disposal site. No material or water would be discharged from the barge while it is in transit. For in-water disposal, when the barge arrives at the appropriate disposal site, the bottom would be opened to dump the material all at once. A clamshell or excavator would be used to unload barges for upland disposal. The barge would then be returned to the dredging site for additional loads. The contractor could be expected to work between 10 and 24 hours per day, 6 to 7 days per week. Dredging would be performed within the established in-water work windows, which currently are December 15 through March 1 in the Snake and Clearwater Rivers and December 1 to March 31 in the Columbia River. Multiple shift dredging workdays would be used when necessary to ensure that dredging was completed within these windows. Dredging outside these work windows, such as summertime, would be subject to coordination with LSMG and state and federal resource agencies and would meet the requirement of NEPA, Clean Water Act, Endangered Species Act, and other applicable environmental laws.

Multiple shift dredging workdays would be used when necessary to complete dredging within the work windows. Mechanical dredging methods would likely be used. The disposal plan would be the beneficial use selected for that dredging activity. Figure 2-7 displays the decision tree that would be used by the Corps to determine the disposal method and location for each activity.

 

Figure 2-7. Disposal Site Selection Decision Tree

Maintenance of irrigation intakes and beaches has often required small-quantity dredging [under 5,000 cy (3 822.8 m³)]. Small-quantity dredging projects would involve either mechanical methods or non-agitation hydraulic methods (irrigation int akes only) and would include discharging to barge or truck for transport. If a truck were used, disposal of the material would be made on an appropriate upland site. Appropriate upland disposal sites include, but are not limited to, Corps land, beneficia l use upland applications, and local landfills. The mechanical dredging equipment for these small dredging projects may be a clamshell, dragline, backhoe, or shovel/scoop. This small quantity dredging activity would use the in-water work window or possib ly an alternate summer work window if one were approved for the specific project.

Following are descriptions of dredging activities anticipated in each of the five reservoirs in this system. The dredging areas described and depicted on the plates are intended as an inclusive list of dredging locations that might be dredged in the 20-year period of this DMMP/EIS. Many of the areas listed and shown on the plates are not considered to need maintenance dredging in the near future.

2.8.1.1 Lower Granite Reservoir

Maintenance dredging in the Lower Granite reservoir may be done at several sites (plates 15 through 17). The largest concentration of dredging would be at the confluence of the Snake and Clearwater Rivers in the Lewiston-Clarkston area. The area that requires frequent dredging extends from the vicinity of Silcott Island near Snake RM 131 upstream to the U.S. Highway 12 bridge located near Snake RM 139.5 and from the confluence at RM 139 up the Clearwater River to just downstream of Memorial Bridge at RM 2 as shown on plate 17. The Federal navigation channel extends to within 50 feet (15.2 m) of existing port structures and the Corps is responsible for maintaining this channel. The port areas parallel the Federal channel and the ports are responsible for maintaining access from the Federal channel. Ports have expressed interest in entering into an agreement for the Corps to dredge these areas. The dredging area includes the Federal navigation channel and port facilities in the area. Areas in the Lower Granite reservoir that may require dredging at some time over the next 20-year period include the Port of Wilma slip, the Port of Clarkston berthing area on the Snake River, the Port of Lewiston berthing area on the Clearwater River, the Green Belt Boat Basin, Potlatch Corporation dock, Hells Gate State Park moorage, Chief Looking Glass moorage, Hells Canyon Resort marina, and the irrigation intake for Chief Timothy HMU.

2.8.1.2 Little Goose Reservoir

Maintenance dredging in the Little Goose reservoir (plates 12 through 15) would include the Federal channel downstream of the Lower Granite navigation lock guidewall and the Federal channel opposite Schultz Bar, RM 101.5. Dredging may also be required to maintain navigation facility clearances at the Port of Garfield, Port of Central Ferry, Port of Almota, and Boyer Park Marina. In addition, small dredging projects of 5,000 cy (3 822.8 m³) or less would be required at the irrigation intakes of the Ridpath, New York Bar, Willow Bar, and Swift Bar HMU's over the 20-year period.

2.8.1.3 Lower Monumental Reservoir

In Lower Monumental reservoir (plates 10 through 12) periodic dredging may be required to maintain adequate navigation clearances into Little Goose navigation lock and at Lyons Ferry Dock and Marina. Small dredging projects may also be required to maintain the irrigation intakes for Skookum and 55 Mile HMU's.

2.8.1.4 Ice Harbor Reservoir

Maintenance dredging in Ice Harbor reservoir (plates 8 through 10) is required periodically for the Lower Monumental navigation lock approach channel and may be required to provide navigation clearances at Walla Walla Grain Growers at Sheffler, Louis Dreyfus Windust Station, and Charbonneau Park boat moorage. Also, small amounts of dredging may be required periodically to maintain the irrigation intake for the Big Flat, Lost Island, and Hollebeke HMU's.

2.8.1.5 McNary Reservoir

In McNary reservoir (plates 2 through 8) navigation maintenance dredging is required in the downstream approach channel to Ice Harbor navigation lock for a length of approximately 7 miles (11.3 km). Periodic dredging may also be required at the Port of Umatilla; the Port of Benton barge slip; the Port of Pasco marine terminal, barge slip, and container terminal; the Port of Walla Walla facilities; and the Pasco Boat Basin.

2.8.2 Dredging Template Design

The navigation dredging template of the Federal navigation channels in this system is 250 feet (76.2 m) wide and 14 feet (4.3 m) deep below the minimum authorized pool elevation. The authorized minimum pool elevations are: 733 feet msl at Lower Granite; 633 feet msl at Little Goose; 537 feet msl at Lower Monumental; 437 feet msl at Ice Harbor; and 335 feet msl at McNary. Dredging templates for other maintenance dredging activities would vary.

2.8.3 Dredging Quantities

Dredging quantities presented here assume a dredging cycle of 2 years; however, actual dredging frequencies are dependent on variable sedimentation rates and actual dredging cyc les may vary from 2 to 10 years. For planning purposes, the maximum volume of dredged material was estimated to be 300,000 cy (229 367 m³), based on a 2-year cycle, in order to maintain the designed navigation channels in the Lower Granite reservoir. Estimated dredging cycles and dredged material volumes for the lower Snake River and McNary reservoirs are presented in table 2-10.

2.8.4 Material Types

The type of material to be dredged depends on the location of the dredging. In the Snake/Clearwater Rivers confluence area, the Corps expects to find a mix of coarse and fine sand, silt, fine silt, and organic material (wood particles). This determination is based on samples taken during previous dredging operations. The Corps expects to find sand in the main navigation channel and silt/fines near the shore in such locations as the port areas and the Greenbelt Boat Basin. In the area below the Lower Granite navigation lock, the Corps expects to find river cobbles 2 to 6 inches (5.1 to 15.2 cm) in diameter with little fines and possibly some large rock up to 18 inches (45.7 cm) in diameter. Samples taken earlier from the Ice Harbor navigation channel indicate the material is rock with some river cobble (Corps 1997). The materials expected in the downstream approach channel of Lower Monumental based on previous Corps experience is river cobble and rock (Corps 1997). In general, dredged materials would be composed mostly of sediments containing a mixture of silts, sands, gravels, and cobbles carried by inflowing waters as suspended and bedload material. Based on previous dredging experience, 85 percent of the material to be dredged is expected to be sands, gravels, and cobbles and 15 percent of the material is expected to be silts and finer-grained material.

2.8.5 Dredged Material Management Process

2.8.5.1 Beneficial Uses Option

Each time a dredging activity covered under this DMMP/EIS is planned, the following steps would occur:

• The Corps would notify parties such as the ports, municipalities, environmental groups, agencies, and others known to have an interest in the beneficial use of dredged material. The Corps would provide the location, estimated quantity, dredging method, expected characteristics of dredged material, and estimated time of the dredging activity. The Corps notification would precede the proposed dredging activity by several months to allow time to negotiate an agreement with a local sponsor for the beneficial use of the dredged material.

• A public notice would be published and distributed prior to the dredging activity.

Beneficial uses may be performed by the Corps at its own expense or beneficial uses may be achieved when a local sponsor is willing to contribute a share of the cost. Beneficial uses performed by the Corps must be the least costly while meeting environmental requirements and being consistent with sound engineering practices. Beneficial uses cost-shared with a local sponsor do not have to be the least costly. Section 204 of Water Resources Development Act of 1992, as amended, authorizes the Secretary of the Army to implement projects for the protection, restoration, and creation of aquatic and ecologically related habitats, including wetlands. Project implementation is conditional, based on non-Federal interests entering into a cooperative agreement to provide 25 percent of the cost associated with project construction and agreeing to pay 100 percent of operation, maintenance, repair, replacement, and rehabilitation costs. The cost of a beneficial use project is the difference between the base dredging disposal cost and the dredging and disposal costs of the beneficial use project. Dredged material may also be used in other ways, provided additional cost to the U.S. government is not incurred. This DMMP/EIS identifies the basis for determining the least-cost option for dredged material disposal. At any time, the Corps, with the consent of a non-Federal interest, can identify another beneficial use, and the non-Federal interest would be given reasonable opportunity to finance the additional cost.

The opportunities that currently exist and could be considered for early implementation are:

• Fish Habitat Creation (Figure 2-8)

• Woody Riparian Habitat Creation

• Hanford Site Capping (Federal)

• Potting Soil (business)

• Riparian Habitat Restoration

• Port of Wilma Fill

• Fill of Non-Federal Public Land

• Highway or Road Construction

These opportunities are described in detail in section 2.5.4.

 

Figure 2-8. Cross Section of the Phased Development Disposal Technique for Creating Shallow Water Habitat

2.8.5.2 Unsuitable Material Disposal Option

A contingency upland disposal site has been identified to provide storage for dredged material that may, for whatever reason, need to be deposited on a separate upland site. A dredged material evaluation framework would be used to guide the evaluation of dredged materials and determine the appropriate management of those sediments (see Section 3.9). Based on existing sediment data, contaminated sediments that would be unsuitable for in- water disposal or other beneficial uses (per the framework) are not expected to be found in substantial quantities. In the improbable event that dredged material may be moderately contaminated, unsuitable for disposal in-water, but suitable for disposal in an unlicensed upland site, it would be isolated at the Joso upland disposal site (RM 56.5 to RM 58.6), and appropriate confinement measures would be taken to isolate this material (e.g., installation of an impervious liner to prevent leaching of unsuitable or contaminated materials). Should the material be uncontaminated, but not suitable for disposal in-water (e.g., too much silt for use in creating shallow-water fish habitat), the material would be disposed of at Joso, but in a different location from the moderately contaminated material.

Any use of the Joso site would require reconstruction of some facilities and construction of others. The existing barge slip would need to be dredged to restore access. The barge slip would also be reconstructed using anchored sheet pile to provide vertical walls and tie off facilities. Temporary dredged material dewatering and storage areas with containment berms and detention ponds would be constructed adjacent to the slip. The material would be off- loaded from the barges and placed in the temporary storage for dewatering, then would be loaded onto trucks for transport to the disposal area. The material would then be placed in lifts using track-type tractors and compacted, resulting in a large structural fill conforming to the established final topography for the disposal area. Areas that reach final grades would be restored on a periodic basis by placing 6 inches (15.2 cm) of topsoil and re-seeding with native grasses to achieve a vegetative cover similar to the surrounding site areas. Filling the gravel pit with sediment and seeding it to grass would improve the site's value as wildlife habitat.

Construction of the Joso facilities would likely be done in stages, depending upon availability of funding. The first stage would include dredging the barge slip and developing the off-loading and temporary storage facilities. If needed, this construction would begin in fall 2002 so the site will be ready to accept any unsuitable material dredged during the proposed 2002-2003 dredging. The temporary storage facilities would have the capacity to contain all the material directed to the site in 2002-2003 without requiring removal of any of the material to the permanent storage areas on the site. The second stage would be the construction of the containment berms, liner, and access roads for the permanent storage areas. These will be constructed concurrently with the temporary storage facilities if funding is available. If funding is not available the first year, they will be constructed at the first opportunity when funds do become available.

2.8.6 Levee Raise

For the 3-foot (0.9-m) levee raise alternative, an earth embankment raise is proposed. The levees would be raised a maximum height of 3 feet (0.9 m) and would consist of removing recreation paths and adding height to the levee using embankment of impervious gravel (20 percent to 30 percent fines). Generally, the side slopes would be 2:1 on the front slope (river side) with flatter back slopes to accommodate local conditions. A 12-foot (3.7-m) top width would be provided for access and maintenance and recreational paths would be reestablished. The top of the existing levee would first be excava ted to the impervious core and filter to allow the new impervious gravel backfill to tie to the existing core and filter. In areas or conditions that require a 2-foot (0.6-m) or less raise, the extended levee slopes would be steepened to 1.5:1, providing the additional levee height without changing the footprint or impacting adjacent facilities. Highway 129 and Snake River Road upstream of Asotin would be modified.

The levee raise would not occur until after 2005. There is little risk of flooding in the near term since the next few dredging operations for navigation channel maintenance would also provide additional flow conveyance capacity in the Lewiston area, even though the protection level would remain below the SPF. However, delaying the levee cons truction date until after 2005 would allow consideration of the biological information available at the checkpoints in 2003 and 2005 for the NMFS 2000 Biological Opinion for Reinitiation of Consultation of the Federal Columbia River Power System, Including the Juvenile Fish Transportation Program, and 19 Bureau of Reclamation Projects in the Columbia Basin, which may impact the status and operating criteria of the four lower Snake River dams and reservoirs. Once the future operating criteria has been determined, and if that criteria still requires a levee raise, the construction could begin once funding is made available.

2.8.7 The 2002-2003 Dredging

The Corps has identified the first dredging activity that would be conducted under the DMMP/EIS. This dredging is currently proposed for winter 2002-2003 and includes dredging the navigation channel at the confluence of the Snake and Clearwater Rivers, several port facilities in the Lewiston-Clarkston area, several recreation facilities in Lower Granite and Little Goose reservoirs, navigation lock approaches to Lower Granite and Lower Monumental, and several other potential areas. The Corps briefed the LSMG, which provided input on the proposed 2002-2003 dredging and dredged material management. The Corps is currently proposing using woody riparian habitat creation at Chief Timothy as a primary beneficial use of dredged material. In-water disposal to create fish habitat in Lower Granite reservoir (RM 116) would be a secondary beneficial use of the dredged material if biological surveys indicate the Chief Timothy site would not be available. Appendix N provides a detailed description of the proposed dredging areas, the disposal plan, the sediment contaminant analysis, and the environmental impacts specific to this dredging activity.

2.8.8 Monitoring

The Corps anticipates the need to perform various types of monitoring of the dredging and disposal activities. Appendix M presents the proposed monitoring program for the DMMP. Monitoring would include the following parameters:

• water quality and sediment quality;
• biological;
• physical;
• cultural resources.

Appendix M describes the process for determining monitoring needs and methods. Monitoring activities will be coordinated with the LSMG.

2.8.9 ESA Consultation Provisions

The Corps consulted with the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS), pursuant to the requirements of the Endangered Species Act (ESA). The Corps prepared biological assessments (BAs) evaluating the potential effects of the proposed alternatives on species listed under the ESA. Full documentation of these consultations is presented in Appendix F (for NMFS) and Appendix G (for the USFWS).

NMFS determined, based upon implementation of a series of Reasonable and Prudent Measures, the Recommended Plan would not cause jeopardy to, or adversely modify the Critical Habitat of anadromous fish species listed under the ESA. Specifically, the Biological Opinion determined that the effects of the Recommended Plan will not jeopardize the continued existence of endangered Snake River sockeye, threatened Snake River Fall chinook, threatened Snake River Spring/Summer chinook, threatened Snake River Basin steelhead, endangered Upper Columbia River Spring chinook, endangered Upper Columbia River steelhead, or threatened Middle Columbia River steelhead or result in the adverse modification or destruction of their Critical Habitat.

The Corps completed informal consultation with USFWS for ESA- listed non-anadromous fish and terrestrial species that might be affected by implementation of the DMMP. In their concurrence letters, USFWS identified several conditions or assumptions, including the need for consultation on specific dredging and associated actions and compliance with the terms of the USFWS Biological Opinion for the Federal Columbia River Power System regarding bull trout in the lower Snake River system (see Appendix G). The Corps intends to comply with these conditions when implementing the DMMP.

2.8.10 Regional Acceptability and Public Comments

The acceptability by states, other Federal agencies, stakeholders, special interests, local governments, tribes, and the general public was assessed through the public review process for the DMMP/EIS and approximately 28 comments of the parties were considered in this Final DMMP/EIS. It seems generally accepted that to maintain the current navigation activities, maintenance dredging and disposal of resulting dredged material must be done. However, the public review process revealed that regional interest focused on water quality, ESA-listed fish species, and cultural resources. Several commentors expressed concerns regarding possible impacts from the proposed dredging and disposal activities within the project area. The method and timing of the dredging and location of disposal is of interest to the public and stakeholders. The local governments affected by the levee raise have concerns with timing and the effect it might have on future river front development. For review of these comments and responses, see Appendix O, Response to Public Comments. The Corps considered all of these comments in the evaluation and selection process to identify the recommended plan (preferred alternative). In an environment as described above, the recommended plan (preferred alternative) will be acceptable to some and not to others. Regarding state or local laws and regulations, the actions in the recommended plan (preferred alternative) are considered to be consistent. See Sections 5 and 6 for more specifics.

2.8.11 Other Considerations

Other important factors that were considered include, but are not limited to:

• How the alternatives affect long-term and short-term productivity

• If there are irreversible and/or irretrievable commitment of resources

• If there are unavoidable adverse impacts

• If mitigation is needed or required

• Whether the best information or science was available

• Which alternative is environmentally preferable

• Whether the recommended plan (preferred alternative) is in accordance with declared policies of NEPA and in compliance with Federal laws and regulations.

Other factors involving technical feasibility were considered. Even though this is a very basic criterion, it is an extremely important one, in that the recommended plan (preferred alternative) must be constructible and implement able. The rationale for selecting Alternative 4, Maintenance Dredging with Beneficial Use of Dredged Material and a 3-foot (0.9-m) Levee Raise, is a composite of analyses, information briefings, evaluations, hundreds of years of combined technical expertise, and comments concerning the factors that may or may not be affected by the alternatives discussed in the DMMP/EIS. The selection of the recommended plan (preferred alternative) resulted from the evolution and development of a collection of scientific data and information presented in this DMMP/EIS, its associated appendices, and supporting research materials and reports. Although not without uncertainties, the information contained herein was the result of researchers, contractors, Corps' staff, etc. and, in the Corps' judgment, is the best available science and information to date and contains sufficient rationale for selecting this plan/alternative.

This section presents the existing environmental conditions in the DMMP study area that could be affected by the alternatives considered in this EIS. The descriptions of the biological, physical, cultural, and socioeconomic resources serve as a basis for evaluation and comparison of the anticipated effects of the plan alternatives evaluated in section 4. In most cases, sufficient existing data and documentation were available to allow reasonable assessments of the impacts to a particular resource. The Feasibility Study, the Corps Interim Columbia and Snake River Flow Improvement Measures for Salmon Final Supplemental EIS (Corps, 1993), the Final Columbia River System Operations Review EIS (BPA et al., 1995), and the Columbia River Flow Measures Options Analysis (Corps, 1992) evaluated some of the same resources and are incorporated by reference. For some resources, only limited data were available. In these instances, the limitations of the data are documented and the impact analysis was more qualitative in nature.

3.1 AQUATIC RESOURCES

Construction of the Snake and Columbia River Federal dams altered the character of the natural river from running to impounded water and created over 124 miles (200 km) of reservoirs on the lower Snake River and 62 miles (100 km) of reservoir behind McNary on the Columbia River. A continuing effect of dam construction is the deposition of sedimentary material in the lower velocity areas within the system. For example, in Lower Granite reservoir, sediment deposition has occurred around the confluence of the Snake and Clearwater Rivers and downstream to Silcott Island. The Corps is proposing to conduct navigation and maintenance dredging on the lower Snake River, the mid-Columbia River (specifically McNary reservoir in Washington and Oregon), and at the mouth of the Clearwater River in Idaho and Washington.

This section describes the lower Snake River and McNary reservoirs, some of their characteristics, and the habitats used by the various fish species. A summary of available data on fish spawning requirements, life histories, and predation of resident fish on juvenile salmonids is also presented.

3.1.1 Fish

The Columbia and Snake River systems support large and varied populations of fish. Within the project area, anadromous salmonids including chinook (O. tshawytscha), coho (O. kisutch), and sockeye (O. nerka) salmon and steelhead (Oncorhynchus mykiss) are seasonally present. Resident fish, of both native and introduced species, are also abundant in these reservoirs with community structure generally similar among reservoirs (Bennett et al., 1983). Of the current resident ichthyofauna of the reservoirs, about half are native species and half are introduced. Major resident species of concern include the white sturgeon (Acipenser transmontanus), northern pike minnow (Ptychocheilus oregonensis), and smallmouth bass (Micropterus dolomieu).

3.1.1.1 Anadromous Fish

Seven anadromous fish species found within the project area have been designated as Evolutionarily Significant Units (ESU's) and are listed as Threatened or Endangered under the ESA. These species include Snake River Sockeye Salmon, Snake River Basin Steelhead, Snake River Basin Spring/Summer and Fall Chinook Salmon, Upper and Middle Columbia River Basin Steelhead, and Upper Columbia River Spring Chinook Salmon. Within the project area, Columbia River stocks are thought to occur primarily in McNary reservoir with few straying into the Snake River. Snake River basin stocks occur throughout the lower Snake River and McNary reservoir. Although not presently listed, Pacific lamprey is also a species of concern in the project area. Historically, white sturgeon exhibited diadromus behavior in the project area but were isolated after construction of the dams and will be discussed in the resident fish section.

The following analysis addresses a small portion of the total life history of these fish with emphasis placed on the threatened or endangered stocks. While a salmon or steelhead typically lives for 3 to 6 years, the duration spent within the direct influence of the hydro system is limited. The Corps is concerned, however, with that period of fresh water residence when the Federal Columbia River Power System (FCRPS) does specifically influence these stocks. This period may occur for a few days to a few months as juvenile salmonids either migrate through these areas or rear within them prior to migrating to the ocean. Also, depending on the stock of fish, adults will be influenced by the FCRPS for weeks to months as they migrate upriver. The life history and status of various stocks, with emphasis on those originating in the Snake River and McNary reservoirs and their headwaters, are presented in this section with migration windows shown in figure 3-1.

 

Figure 3-1. Typical Anadromous Salmonid Migration Windows

3.1.1.1.1 Sockeye Salmon

One run of ESA-listed sockeye salmon is known to occur in the project area. Snake River sockeye salmon were listed as endangered in November 1991.

Sockeye salmon are unique in that they are the only species of Pacific salmon that depends on higher elevation tributary lakes in the Salmon River subbasin of Idaho for spawning and rearing (Gustafson et al., 1997). Adult Snake River sockeye salmon passage typically occurs in the project area from June through early August. Juveniles rear in lakes for 1 to 2 years and typically actively migrate to the ocean (with minimal rearing in the reservoirs) from April to July; however, some migration can occur through November.

The McNary reservoir and the lower Snake River corridor are designated as Critical Habitat for migration passage of wild Snake River sockeye salmon. Critical Habitat attributes and Essential Fish Habitat (EFH) components for potential rearing or overwintering for Snake River sockeye salmon are not present in the McNary reservoir, lower Snake River corridor, or any of the proposed project areas. The components of designated Critical Habitat and EFH for juvenile and adult migration passage are present between mid-March and mid- August. No spawning habitat for sockeye salmon is present in the proposed project area. Therefore, no individuals should use the dredging activity areas of the Columbia, Snake, or Clearwater Rivers for rearing, feeding, or overwintering during the designated in-water work period. This includes the off-channel areas that will only be dredged when water temperatures exceed 73 °F (22.7 °C). The high temperatures make the proposed dredging areas unsuitable for sockeye salmon.

3.1.1.1.2 Spring/Summer Chinook Salmon

Two runs of ESA- listed Spring/Summer Chinook Salmon seasonally exist in the project area. These include the Upper Columbia River Spring ESU, listed as endangered in 1999, and the Snake River Spring/Summer ESU, listed as threatened in 1992.

Upon returning to fresh water after spending 2 to 3 years in the ocean (Howell et al., 1985), adult spring chinook salmon typically pass through the McNary and Snake River reservoirs from mid-April to mid-June with 90 percent passing in the month of May (Stuehrenberg et al., 1995). Adult summer chinook salmon typically pass the main stem dams by September, with the majority passing between mid-June and mid-August. All populations are believed to spawn from August through October in tributaries upstream of hydro project influences (Corps, 1999). In tributary systems with both spring and summer runs, spring chinook salmon tend to spawn farther upstream and earlier than summer run salmon (Matthews and Waples, 1991); however, spawning area and timing may overlap in some areas. This overlap is one of the reasons that NMFS may designate these fish as one stock (spring/summer) in their ESA listing. Within the Snake River system, there are five major spawning and rearing basins for spring/summer chinook salmon. These include the Clearwater, Grande Ronde, Salmon, Tucannon, and Imnaha rivers. Columbia River stocks spawn and rear in the Wenatchee, Entiat, Methow, and Okanogan basins.

Juveniles typically rear in the tributaries for more than a year, migrating downstream during their second spring as yearlings from about early April to June. Snake River spring and summer chinook salmon have the same juvenile out-migration age and timing, with the majority of these fish passing the dams in April and May. Little, if any rearing occurs in the main stem Snake and Columbia Rivers (Chapman et al., 1995) as indicated by a relatively short reservoir residence time of juvenile spring chinook salmon (Giorgi and Stevenson, 1994). However, a few individuals of spring chinook salmon from undetermined origin have been documented as using backwater areas of the McNary reservoir for rearing, feeding, or overwintering (Easterbrooks, 1995, 1996, 1997, 1998) during the period sampled (mid-March through July).

The McNary reservoir is designated as Critical Habitat for migration passage of wild Upper Columbia River Spring and Snake River Spring/Summer Chinook Salmon. Designated Critical Habitat and EFH for potential rearing, overwintering, or resting during juvenile migration may be present in the McNary reservoir project areas for Upper Columbia River Spring Chinook Salmon between mid-March and mid-June.

The lower Snake River was designated as Critical Habitat for migration passage of wild Snake River Spring/Summer-Run Chinook Salmon. Critical Habitat attributes and EFH components suitable for potential rearing or overwintering for Snake River Spring/Summer-Run Chinook Salmon are likely present in the proposed project areas during the winter in- water work window and in November at the Joso site. No suitable habitat would be available in off-channel dredging areas if water temperatures exceed 73 °F (22.7 °C).

3.1.1.1.3 Fall Chinook Salmon

One run of ESA-listed Fall Chinook Salmon is known to occur in the project area. The Snake River Fall Chinook Salmon ESU was listed as threatened in 1992.

After 2 to 3 years in the ocean, adult wild Snake River Fall Chinook Salmon return to the Snake River between late summer and early winter with spawning activity beginning around mid-October (Connor, 1994). The current major spawning area for Snake River Fall Chinook Salmon exists in the 103 miles (166 km) of the Snake River below Hells Canyon Dam and in the lower reaches of the Clearwater, Grande Ronde, Imnaha, Tucannon, and Salmon Rivers. The majority of redds annually appear clustered in specific areas, such as at Snake River RM 162 in 1991 (Connor, 1994). Spawning of fall chinook salmon has also been known to occur in Little Goose, Lower Monumental, and Ice Harbor reservoirs, but only in tailwater areas directly downstream of the dams' bypass outfalls, where water velocity is high and substrate is relatively large (Dauble et al., 1995 and 1996).

Little is known about timing of emergence from the gravel for Snake River Fall Chinook Salmon (Howell et al., 1985); however, Bennett and Shrier (1986) and Bennett et al. (1988, 1990, 1991, 1993a, 1993b) captured subyearling chinook salmon in Lower Granite reservoir in April, suggesting emergence can occur in March to early April. After emergence and initial dispersal, fall chinook salmon exhibit a high fidelity for lower velocity backwater areas for rearing in the main stem river and reservoir reaches of the Columbia and Snake Rivers. Bennett and Shrier (1986) and Bennett et al. (1988, 1990, 1991, 1993a, 1993b) consistently captured subyearling chinook salmon over low gradient, low velocity, sandy substrates in Lower Granite reservoir, likely an anti-predation strategy at locations that produce suitable macroinvertebrate prey abundance. Habitat having these physical characteristics can be effectively constructed in any of the lower Snake River reservoirs with appropriate placement of dredged material. Subyearling salmon migrate through reservoirs more slowly than yearling chinook salmon and spend more time in reservoir habitats for rearing (Rondorf et al., 1990; Curet, 1994) since they are not afforded the additional year of freshwater rearing and overwintering in the subbasins that yearling chinook salmon are allowed.

Most juvenile fall chinook salmon from the Snake River migrate to the ocean as subyearlings (Bjornn, 1960). The wild juvenile fall chinook salmon typically pass mid-June through September, with double peaks in mid-July and some lingering proportion of the annual migration population lasting through November. Passive Integrated Transponder (PIT)-tag detections of 1993-1995 brood year juvenile fall chinook salmon from the Clearwater River were recorded in the spring of 1994-1996 at some lower Snake River dams (Arnsberg, 1996). It is apparent from these detections that some fall chinook salmon migrate to the ocean as yearlings rather than as subyearlings.

3.1.1.1.4 Steelhead

Three runs of ESA- listed steelhead are known to occur in the project area. Upper Columbia River and Snake River Basin ESU's were listed in 1997 and the Middle Columbia River ESU's were listed in 1999.

Upon returning to fresh water after spending 1 to 4 years in the ocean, most adult steelhead pass McNary between May and November and Lower Granite between July and December. Some adult steelhead are known to overwinter in the lower Snake River and begin migrating toward spawning grounds the following spring as water temperatures begin to warm up. Steelhead typically spawn in tributaries outside the influence of the hydrosystem between December and June (Bell, 1991). Unlike salmon species, steelhead have the potential to spawn numerous times; however, the current proportion of repeat spawners is expected to be low (Corps, 1999). Adult steelhead may be in the areas proposed for dredging and disposal in the reservoirs during the proposed dredging periods.

Juvenile steelhead rear in freshwater streams for 2 to 3 years prior to out-migrating. Out-migrants actively migrate through the reservoirs from late April through June and typically rear very little during their out-migration.

3.1.1.1.5 Pacific Lamprey

Adult Pacific lamprey enter the fresh water between April and June, migrating to spawning areas by September (Close et al., 1995). Spawning typically occurs in June and July of the following year in low-gradient-flowing- water stream sections where gravel is deposited. Spawning has been observed in small tributaries entering main stem reservoirs (Wydoski and Whitney, 1979). Lamprey distribution extends up the Snake River to Hells Canyon Dam and to Chief Joseph Dam on the Columbia.

After hatching, ammocoetes (a stage of juvenile lamprey) drift downstream to burrow into the substrate sand or mud. Ammocoetes rear in the substrate for 5 to 6 years when they metamorphose into juvenile lamprey and out- migrate to sea between April and July. After 20 to 40 months, the adults return to spawn in the river systems (Kan, 1975).

3.1.1.2 Resident Fish

3.1.1.2.1 General Ecology

Resident fish species in the lower Snake River and McNary reservoirs include a mixture of native riverine species as well as introduced species that are associated with lake- like conditions (Bennett et al., 1983; Bennett and Shrier, 1986; Hjort et al., 1981; Mullan et al., 1986). Cold-water resident species (such as trout and whitefish) that were once common in the Columbia and Snake Rivers have declined since the construction of the dams and have been replaced by cool- and warm-water species. Species composition has changed due to the blockage of spawning migrations and modification of habitats (Mullan et al., 1986). The prey base has also changed since the construction of the dams, probably contributing to the decline of cold-water species (Sherwood et al., 1990).

Resident fish in the reservoirs occupy numerous habitats and often use separate habitats for different life history stages (Bennett et al., 1983; Bennett and Shrier, 1986; Hjort et al., 1981; Bennett et al., 1991). Each reservoir has three general zones that are characterized by different habitats (Hjort et al., 1981). The first zone is the forebay area, which is typically lacustrine (lake-like) in nature. At the upper end of the reservoir is a second zone that tends to be shallower and have significant water velocities. In between these two zones is a transition area that changes in the upstream end from riverine to more lake- like in the downstream direction. Each zone can include several habitat types; however, most can be characterized as either backwater (including sloughs and embayments) or open-water habitats (Hjort et al., 1981; Bennett et al., 1983).

3.1.1.2.2 Habitat Use

Backwaters and embayments generally provide low water velocity, slightly warmer water, finer substrate, and submersed and emergent vegetation. Bass (Micropterus spp.), crappie (Pomoxis spp.), bluegill (Lepomis spp.), yellow perch (Perca flavescens), and carp (Cyprinus carpio) use backwater areas for spawning and rearing (Bennett et al., 1983; Bennett and Shrier, 1986; Hjort et al., 1981; Bennett et al., 1991; Zimmerman and Rasmussen, 1981). The centrarchids (sunfishes, including bass and crappie) normally spawn in shallow water less than 6.5 feet (2.0 m) deep (Bennett et al., 1983) while yellow perch generally utilize waters less that 10 feet (3.0 m) deep (Stober et al., 1979). Spawning and incubation times vary between species; however, most of these backwater species spawn from May through mid-July (Corps, 1999).

Cyprininds (minnows, dace, and chub); catostomids (suckers); walleye (Stizostedion vitreum); and sandroller (Percopsis transmontanus) spawn in open water. White sturgeon, a species that is considered non-anadromous above Bonneville (ODFW and WDFW, 1998), spawn over areas with rocky bottoms and high water velocity (Parsley et al., 1993). Prickly sculpin (Cottus asper) spawn in both open water and backwater based on the distribution of prolarvae (Hjort et al., 1981). Most fish larvae are generally found in the backwaters and near-shore areas. Only yellow perch and prickly sculpin larvae are commonly found in open-water areas. Most of the native species spawn in flowing water at the headwaters of the reservoirs or in tributary streams. Some species, however, also spawn in the reservoirs. Northern pike minnow may spawn either in flowing water or along gravel beaches in reservoirs (Wydoski and Whitney, 1979).

Juvenile fish are found in abundance in backwater and open-water areas where flowing water is found. The two habitats are occupied by distinctly different fish species. Introduced species, which are primarily lake-dwelling fishes, are more common in the forebay zone and backwater areas while native species are more common in the flowing water regions found in the tailrace zone (Hjort et al., 1981; Bennett et al., 1983; Bennett and Shrier, 1986; Mullan et al., 1986).

Adult distribution is generally similar to spawning and juvenile distribution, but can change depending upon feeding strategy. Adults may occur throughout the habitats and move seasonally or daily to different areas (Bennett et al., 1983; Bennett and Shrier, 1986; Hjort et al., 1981). Although adults will use various habitats, lake-dwelling species are generally more abundant in shallow, slower- velocity backwater areas, and native riverine species occur abundantly in areas with flowing water (Bennett et al., 1983).

Although there is a difference in numbers, there is little difference in the species composition of the five reservoirs. Species found in high abundance in all reservoirs include suckers, northern pike minnow, bass, chiselmouth (Acrocheilus alutaceus), and redside shiners(Richardsonius balteatus) (Bennett et al., 1983; Bennett and Shrier, 1986; Bennett et al., 1988). Species such as crappies, sunfish, and largemouth bass are highly abundant in backwaters of all reservoirs. Minor variations in species composition are related to variations in the availability of backwater habitats and flowing waters in the various reservoirs.

Little Goose, Lower Monumental, and McNary reservoirs have a greater number of backwater areas than Lower Granite and Ice Harbor (Bennett et al., 1983). The confluence of two major tributaries (Palouse and Tucannon Rivers) with the Snake River provide additional backwater habitat in Lower Monumental reservoir. These reservoirs tend to support larger numbers of species that depend on shallow-water habitats during some part of their life histories.

3.1.1.2.3 Bull Trout

Bull trout, listed as threatened under the ESA, are found primarily in colder streams, although individual fish are found in larger river systems throughout the Columbia River Basin (Fraley and Shepard, 1989; Rieman and McIntyre, 1993, 1995; Buchanan and Gregory, 1997). Water temperature above 59 °F (15 °C) is believed to limit bull trout distribution. However, the USFWS reported 37 records of bull trout in the lower Snake River since 1991. Most were noted at adult-fish-counting stations and passed in April, May, or June (Hayley, 1999).

Bull trout typically spawn from August to September during periods of decreasing water temperatures. Migratory bull trout frequently begin spawning migrations as early as April and have been known to move upstream as far as 155 miles (249 km) to spawning grounds. Temperature during spawning generally ranges from 39 to 51 °F (4 to 10 °C) with redds often constructed in stream reaches fed by springs or near other sources of cold groundwater (Goetz, 1989). Bull trout require spawning substrate consisting of loose, clean gravel relatively free of fine sediments.

The only subpopulations of bull trout associated with the project area spawn and rear in the Tucannon River Basin with both resident and migratory forms present. Evidence suggests that migratory (adfluvial) bull trout from the Tucannon River also utilize the main stem Snake River on a seasonal basis (Buchanan and Gregory, 1997). Adult bull trout that are adfluvial generally spend about half of every year associated with a reservoir (November-May). These fish most likely forage in shallow areas where the majority of prey exists. Depending on water conditions, bull trout will occupy deeper areas of the reservoir where water temperatures are cooler [45 to 54 °F (7.2 to 12.2 °C)] and move to the surface when water temperatures drop to or below 54 °F (12.2 °C).

There have been several observations of adult bull trout passing Lower Monumental and Little Goose. From 1994 to 1996, 27 bull trout passed the adult fish counting station (mainly in April and May) at Little Goose. At least six bull trout passed counters at Lower Monumental and Little Goose in 1990 and 1992 (Kleist, 1993). Kleist also observed one bull trout in 1993 just downstream of the count window at Lower Monumental. Furthermore, one bull trout was captured in the Palouse River below Palouse Falls in 1998. These were likely migratory fish from the Tucannon River. However, one bull trout was observed at Lower Granite in 1998 that may indicate fluvial fish are migrating to other upstream populations.

The status of bull trout associated with the Tucannon River was rated as "healthy" by the Washington Department of Fish and Wildlife (WDFW, 1997), although some habitat degradation has occurred due to timber harvest and recreational use. It is not currently at risk of extinction and is not likely to become so in the foreseeable future because of sufficient habitat protection (wilderness designation) in the upper watershed and the lack of brook trout encroachment.

3.1.1.2.4 White Sturgeon

Historically, diadromus white sturgeon in the Columbia and Snake River system ranged freely and made extensive seasonal migrations to optimize changing habitats (Bajkov, 1951). Dams and resulting impoundments have isolated white sturgeon populations (North et al., 1992) and reduced habitat diversity by replacing riverine habitats with lentic environments. Populations of fish species adapted to riverine conditions typically decline at the highest rate (Parsley et al., 1993). Landlocked populations of white sturgeon in the Snake River are classified as a species of special concern (Mosley and Groves, 1990 and 1992) for the states of Washington and Idaho.

Presence of young of the year (YOY) and high abundance of juvenile white sturgeon in Lower Granite reservoir indicate recruitment has been occurring in the Lower Granite-Hells Canyon population. The high abundance of juvenile and YOY fish near the upper end of Lower Granite reservoir also suggests that the reservoir primarily serves as rearing habitat. McCabe and Tracy (1993) suggested that wide dispersal of white sturgeon larvae allowed more use of feeding and rearing habitats while minimizing competition. Lepla (1994) assumed no spawning occurred in Lower Granite reservoir since velocities measured in the reservoir [0.0 to 1.96 feet per second (0.0 to 0.60 meters per second (m/s))] are below threshold levels perceived to elicit spawning [3.28 feet per second (1.0 m/s)] (Anders and Beckman, 1993).

Parsley et al. (1996) captured YOY fish and fertilized eggs in 1994 and 1995 in the tailraces of Priest Rapids and Ice Harbor, indicating that recruitment has been occurring in McNary reservoir. Rien and Beinegen (1997) reported the density of white sturgeon in McNary reservoir was 0.86 fish/acre (0.35 fish/hectare), which is similar to John Day reservoir in 1990, but much less than Bonneville or The Dalles reservoirs in 1994. The estimated proportion of white sturgeon less than 32.3-inch (82-cm) fork length in the population estimate was smaller than that in the lower reservoirs. While this estimate may be negatively biased by gear limitations, low recruitment is likely limiting abundance.

Seasonal changes in distribution occur in Lower Granite reservoir (Lepla, 1994). Relative numbers of white sturgeon in the upper section of the reservoir increased from May through November, implying upriver redistribution/movement as the summer to fall season progressed. However, multiple comparison tests indicated seasonal use of mid- and lower reservoir transects was not significant with exception to RM 116.8 (1.6 RM upriver of Knoxway Bay). The number of white sturgeon sampled at RM 116.8 was highest (0.31 fish/hr) only during April-July 1991 and declined sharply as summer progressed. Catch rates at RM 116.8 in 1990 were low and were also similar in 1992 (Bennett et al., 1994 and 1995). Catch rates at remaining mid- and lower reservoir locations were low regardless of season. Movements from 0 to 16 miles (0 to 25 river km) were observed from recaptured white sturgeon with the majority of fish traveling 0.62 to 3.1 miles (1 to 5 river km). Differences in fish size did not appear to affect distance traveled in the reservoir. Approximately 65 percent of the fish recovered were collected within the upper 6.21 miles (10 river km) of Lower Granite reservoir where densities of white sturgeon were highest.

3.1.1.2.5 Margined Sculpin

Margined sculpins, a federal species of concern and considered a sensitive species by the state of Washington, are a small fish species that live in river gravels/cobbles whose requirements are poorly known. The former range of these sculpins is unknown; however, they currently inhabit the Walla Walla and Tucannon Rivers in Washington. Without competition, they seem to prefer cool [55 to 66 °F (12.8 to 18.9 °C)] water, moderate to rapid current, and rubble or gravel substrate. Margined sculpins spawn in the spring.

3.1.2 Plankton and Benthic Organisms

3.1.2.1 Plankton

Two other very important parts of the food chain that may be affected by dredging and disposal activities include phytoplankton and zooplankton. Both phytoplankton and zooplankton are food sources for larger aquatic organisms, such as snails and small fish. In addition, zooplankton can compose an important component to the diet of rearing anadromous and resident fish species (Bennett et al., 1983). The use of backwater areas by numerous species may be at least partially related to the availability of prey. High concentrations of zooplankton in the backwater areas attract smaller prey species that feed upon these organisms. In turn, high concentrations of prey fish attract larger predator fish species. Therefore, higher concentrations of zooplankton in backwater areas may affect the habitat selection of several species (Corps, 1999).

3.1.2.2 Benthic Organisms

The benthic community consists of organisms that live on the river bottom and provide significant input into the food chain. Benthic plants such as algae and benthic animals such as insects, worms, snails, and crayfish are components of this community. Benthic organisms contribute significantly to the diets of many reservoir fish species (Bennett et al., 1983). In particular, crayfish are an important component to the diet of smallmouth bass, northern pike minnow, and channel catfish (Ictalurus punctatus) in Little Goose and Lower Granite reservoirs (one can assume these species would be equally important in Lower Monumental, Ice Harbor, and McNary reservoirs). Benthic production is usually minimal in shallow-water areas if the water levels fluctuate and expose the organisms.

As reservoirs age, the invertebrate species composition and abundance convert from lotic flowing riverine macroinvertebrate species found in the shallower and higher velocity environments of the pre-dam river to lentic or pelagic reservoir invertebrate species found drifting in the photic zone of the deeper and slower velocity environments of the post-dam reservoir. Species abundance and composition for benthic macroinvertebrates sampled in the early 1980's (5 to 7 years following refill) were related to habitat differences including substrate type and size, depth, flow, and season of year (Bennett and Shrier 1986, Dorband 1980). By the early to mid-1980's, the dominant benthic invertebrate taxa in Lower Granite reservoir had already converted to dipteran chironomid midges and annelid oligochaete (bloodworms) (Bennett and Shrier, 1986; Bennett et al., 1988). Within a few years after reservoir filling, Dorband (1980) already found a shift in dominant benthic taxa at RM 135, approximately four-fifths the distance upriver from Lower Granite near the Port of Wilma. The Port of Wilma is about 4 to 5 RM's above Silcott Island at RM 131 where the hydraulic influence of the unimpounded flow input becomes dominated by the backwater effect of the reservoir volume and lower water velocities. Upriver of RM 135, there were more lotic species (larvae of tricopteran caddisflies, ephemeropteran mayflies, and plecopteran black flies), while below RM 135, lentic taxa were common (dipteran chironomid midges and annelid oligochaete blood worms). The transition zone between the lentic and lotic habitats had the lowest density of benthic macroinvertebrates, possibly attributable to deposition from sediment input where the average water velocity across the channel slows. Species diversity of macroinvertebrate communities at shallow sites increases with downstream movement or colonization of drifting organisms scoured from upriver habitats, provided that like substrate and associated habitat components are available and suitable.

In the early 1980's, shoreline distributed littoral areas [less than 15.5 feet (4.7 m) deep] generally had the highest invertebrate abundance, species diversity, and species evenness. Sites of similar depth within the reservoir appeared different based upon location in the reservoir (as defined by river mile) with regard to benthic invertebrate numbers within and across species (Bennett and Shrier 1986, Bennett et al., 1988). Annual and seasonal population abundance variations occurred, with increased variation evident for species exhibiting seasonal emergence (e.g., chironomids as they pupated into adults) than species that are aquatic through all life stages (e.g., oligochaetes). Oligochaetes are ubiquitous throughout the lower Snake River reservoir sediments. Oligochaete biomass does not appear to vary with depth of water. While the numerical densities can fluctuate widely with a pattern similar to chironomids, the average biomass density appears to remain relatively constant around 0.15 ounce per square yard (oz/yd²) (5 g/m²). Oligochaetes prefer fine sediments with a high percent of organic content.

Chironomids can make up a substantial portion of the diets of certain fishes. If food is a limiting resource to fall chinook salmon rearing and migrating through Lower Granite reservoir, then it is necessary to estimate chironomid densities as a function of depth and substrate type. Sampling by Bennett et al. (1988) showed a statistically weak pattern of biomass and abundance when measured by season and depth. The shallow water biomass peaks in summer at about 0.59 oz/yd² (20 g/m²), and drops off to around 0.15 oz/yd² (5 g/m²) in the winter. Measured by depth, the biomass appears to be constant from 5 to 20 feet (1.5 to 6.1 m) deep, but begins to decrease as depth increases below 20 feet (6.1 m). Chironomids are most likely located in sand-silt sediments and decrease in both finer and coarser sediment-type environments. The chironomid communities within the lower Snake River reservoirs are composed of several different species, thus resulting in chironomids being readily susceptible to predation by rearing salmonid smolts across the duration of the smolt migration seasons during each of the overlapping pupation and emergence episodes of the various chironomid species.

The role of crayfish in resident and predatory fish diets is extensively reported for every year of sampling in both Lower Granite reservoir since 1988 (Bennett, 1988) and in the unimpounded Snake River upriver of Lower Granite reservoir (Nelle, 1999; Petersen et al., 1999), especially for sustaining northern pike minnow and smallmouth bass. Crayfish predominantly inhabit shallow water riprap areas from which they forage riverward for primarily oligochaetes and other soft substrate inhabitants. Crayfish have been found at all depths in the Oxbow reservoir above Hells Canyon (Bennett, 1995), in Lower Granite reservoir during the physical drawdown test in 1992 (Bennett et al., 1995; Curet, 1994), and in the unimpounded Snake River between Lower Granite reservoir and Hells Canyon Dam (Nelle, 1999). To demonstrate the importance of crayfish in sustaining predator productivity in both Lower Granite reservoir and the unimpounded Snake River between Lower Granite reservoir and Hells Canyon Dam, Bennett et al. (1995) observed a vertical migration of smallmouth with the 2 feet (0.6 m) per day receding water during the physical drawdown test of Lower Granite reservoir in March 1992. Crayfish were left desiccated as they searched wetted shelter in the sediment cracks of the 30-foot- (9.1-m-) deep zone that was dewatered for several weeks. When the reservoir refilled in late March and early April, the majority of the smallmouth bass survived and vertically migrated back up to the shallow water zones that had cover via riprap when spring chinook smolts began migrating. Smallmouth bass consumption rates on juvenile salmonids increased in 1992 compared to previous smolt migration years as a consequence of interception by predators that were occupying a littoral zone that was temporarily devoid of crayfish. Crayfish recruited back to the littoral zone within the year, and smallmouth bass consumption rates decreased in 1993 to similar rates estimated for previous and post years of sampling (Bennett et al., 1995; Bennett et al., 1997).

Studies on the Columbia River have shown the importance of benthic invertebrates, particularly Corophium salmonis, in diets of juvenile white sturgeon (McCabe et al., 1992a; McCabe et al., 1992b). More extensive research is needed to determine significant links between sturgeon distribution, sturgeon growth, and invertebrate abundance. Sprague et al. (1993) indicated that white sturgeon may be feeding on organisms in the water column rather than exclusively on organisms associated with the substrate. Corophium species (river drift organisms) were the predominant prey item eaten by YOY and juvenile white sturgeon in two Columbia River impoundments and the lower Columbia River (Sprague et al., 1993; McCabe et al., 1992a; Muir et al., 1988). Corophium species abundance in Lower Granite reservoir appear low (Bennett et al., 1991); however, crayfish were abundant near the upper end of Lower Granite reservoir.

Cochnauer (1981) reported crayfish and chironomid species were dominant food items identified from white sturgeon stomachs in the middle Snake River. This may explain the high density of juvenile white sturgeon in the upper section of Lower Granite reservoir relative to lower areas of the reservoir. Highest densities of crayfish in Lower Granite reservoir, a prey item of white sturgeon greater than 17.7 inches (45 cm) long (Scott and Crossman, 1973), occurred near the upper end of the reservoir, which coincided with the highest densities of juvenile white sturgeon. Bennett et al. (1990) reported high abundance of larval fishes above RM 127.2, which also may contribute to food resources available to white sturgeon. Lepla's (1994) sampling in 1990-1991 show that the upriver portion of Lower Granite reservoir is the most critical portion of the reservoir for juvenile white sturgeon rearing.

Benthic macroinvertebrates that are commonly consumed by salmonids in the lower Snake River and McNary reservoirs also seem to be largely taxa that are commonly associated with hard substrates. Nightingale (1999) reported differences in the macroinvertebrate fauna of hard versus soft substrates in the lower Snake River and McNary reservoirs. Several taxa of aquatic organisms commonly found in the stomachs of juvenile anadromous salmonids in Lower Granite reservoir were from organisms produced on firm substrates (Karchesky, 1996). Hard substrata in the lower Snake River and McNary reservoirs occur alo ng riprap (Nightingale, 1999) and the original river channel. Some of these organisms "drift" in the upstream portion the reservoirs primarily in the seasons of higher flow that increases their availability to rearing and downstream migrating juvenile salmonids and resident fishes.

Chipps et al. (1997) showed that construction of shallow-water habitat with dredged material has increased habitat complexity in Lower Granite reservoir and proper placement has potential as an enhancement technique. Chipps et al. (1997) concluded that islands constructed from dredged material altered the "natural" reservoir habitat by decreasing depth and, therefore, improving rearing habitat for several resident fishes.

3.1.3 Aquatic and Terrestrial Plants

Aquatic plants within the study area include phytoplankton, algae, and various macrophytes. Each of these plant types is an important component to overall flora production within the reservoirs.

Phytoplankton presence in the Snake and Columbia rivers has been typically measured by sampling for monochromatic chlorophyll a. Ledgerwood et al., 2000, reported peaks in concentrations of chlorophyll a primarily in April before peak flows occurred in Lower Granite reservoir and again in the periods of the declining hydrograph from July until approximately October (depending on location of sampling in the reservoir and year). Gilbreath et al. (2000) reported similar patterns of chlorophyll a prevalence for John Day reservoir during the same time periods of 1994 and 1995.

Filamentous green algae was described as part of the diet for several of the fish species in the Little Goose reservoir, but was not prominent in any diet (Bennett et al., 1983). Filamentous green algae can be found attached to rocks, woody debris, and other structures.

Macrophytes are large plants that typically grow in shallow water along the shorelines of lakes or in the slow-moving reaches of rivers. They can be entirely submerged or emergent. Bennett et al. (1995) reported the presence of two species of pondweed in Lower Granite reservoir including Potamogeton crispus and P. filiformis. Emergent macrophytes are an important element in the food chain because they provide habitat for insects, which, in turn, can be food for fish, and they function as direct food source for many aquatic organisms. They also supply surfaces for fish eggs to incubate as well as protection for fish species during various life stages. These plants are especially important for young fish that hide among plant stems and leaves to escape predators. Macrophytes help stabilize shorelines by reducing erosion and recycling nutrients.

Terrestrial plants growing adjacent to the reservoirs can contribute woody debris, leaf litter, and other organic debris that can be utilized as cover, substrate, and nutrients by invertebrate and vertebrate aquatic fauna if it falls into the water. Terrestrial plants generally do not contribute directly to fish diets. See section 3.2 for further discussion of the terrestrial ecology of the project area.

3.1.4 Fish Predation

The most important fish-eating fish species include smallmouth bass, northern pike minnow, channel catfish, crappies, and yellow perch. Of particular importance, the larger individuals may seasonally forage on juvenile salmonids residing in, or migrating through, the reservoirs. However, other than juvenile fall chinook salmon, fish predation appears to be relatively low in yearling chinook salmon and steelhead (Corps, 1999). The most important single predator on juvenile salmonids is smallmouth bass because of their abundance (Corps, 1999). Predation by northern pike minnow has been substantially reduced in the lower Columbia and Snake Rivers by the Sport Reward Program and scientific sampling funded by BPA (Corps, 1999), both of which remove significant numbers of northern pike minnows.

3.2 TERRESTRIAL RESOURCES

3.2.1 Vegetation

The study area along the Columbia and Snake Rivers passes through steppe and shrub-steppe plant communities (Franklin and Dyrness, 1973; Daubenmire and Daubenmire, 1984). Steppe communities are dominated by bunchgrasses, such as Idaho fescue, bluebunch wheatgrass, and Sandberg's bluegrass, while shrub-steppe communities are co-dominated by sagebrushes, such as big sagebrush. Both the Columbia and Snake Rivers are major migration and dispersal corridors for plants and wildlife and have a high degree of local variation (Franklin and Dyrness, 1973).

Prior to the construction of the dams and impoundments, rich alluvial soils associated with the floodplains allowed the development of quality riparian vegetation along the rivers. Over 50 vegetated islands were present in the Snake River alone with numerous sand and gravel bars common (Technical Appendix M, Corps, 1999).

The construction of the dams and impoundments reduced the native upland and riparian habitats within the study area. Emergent wetland habitat increased significantly after construction of the dams and impoundments due to sedimentation and flooding of backwater areas.

The project reservoirs have influenced the extent and distribution of numerous plant and wildlife communities that have existed within the river corridor for many years. Local plant communities have established under normal reservoir fluctuations and periodic drought. Specifically, riparian, wetland, and shallow-water habitats on the Columbia and Snake Rivers have established under normal, daily reservoir fluctuations of 3 to 5 feet (0.9 to 1.5 m). The following discussion is limited primarily to the major plant and wildlife associations within the project reservoirs, including riparian, wetland, upland, and HMUs.

3.2.1.1 Riparian Communities

The riparian zone includes areas with woody vegetation that are too dry to be considered wetlands, sand and gravel bars, wet meadows, flood-scoured areas, and other stream-related habitats and vegetation. Riparian areas serve as important wildlife habitat and are integral to the function of river aquatic ecosystems, wind shelters for residences, and locations for recreational activities (Corps, 1999).

Currently, approximately 1,804 acres (730.1 hectares) of similar habitat exists in varying proportions along the lower Snake River reservoirs (Corps, 1999). Approximately 2,908 acres (1 176.8 hectares) of riparian communities occur alo ng the McNary reservoir (Corps, 1992).

In general, riparian forests on the lower Snake River are dominated primarily by Russian olive (Elaeagnus angustifolia), but also include black cottonwood (Populus trichocarpa), black locust (Robinia pseudo-acacia), hackberry (Celtis reticulata), and white alder (Alnus rhombifolia). Scrub-shrub vegetation includes coyote willow (S. argophylla), other willows (Salix spp.), and false indigo (Amorpha sp.). Herbaceous plants in this area include dotted smartweed (Polygonum punctatum), cocklebur (Xanthium sp.), thistle (Carduus sp.), and mustard (Brassica sp.). A few large sandbars and islands occur along the river that also support plant communities typically dominated by licorice root (Glycyrrhiza lepidota), cocklebur, and willows.

Riparian vegetation is abundant along the McNary reservoir in the Columbia River. This is an extremely diverse area consisting of numerous islands, shallow-water and backwater areas, riparian forests, and wetlands. Deciduous riparian trees in this area are some of the largest in the region. In general, deciduous riparian trees associated with the projects are characterized by (in order of abundance) Russian olive, willows, and black cottonwood. Riparian shrubs include willows, dogwood (Cornus sp.), and rose (Rosa sp.). Riparian herbs include a mixture of various forbs and grasses that occupy sand, mud, and gravel bars in the reservoir areas (Asherin and Claar, 1976; Tabor, 1976).

A number of factors contribute to the lack of extensive riparian areas along the lower Snake River and Columbia River (Corps, 1992; Corps, 1999). The steep shorelines associated with project reservoirs are primarily responsible for limiting development of riparian communities in the study area. Furthermore, ext ensive grazing (Lewke and Buss, 1977), the expansion of railroads, and the gradual inundation of the river bottom by dams have also limited riparian vegetation to narrow vegetation corridors and backwater areas. The woody plant community that remains in the study area is drought resistant and composed of black locust, Russian olive, and various hybrid cherries (Prunus sp.) (Asherin and Claar, 1976).

Since 1976, much of the shoreline has been fenced to limit cattle grazing to selected cattle watering corridors along the lower Snake River. Much of the existing vegetation has rebounded with the removal of cattle grazing. However, cattle watering corridors do still exist.

3.2.1.2 Wetland Communities

Wetlands along the river and inside stream deltas serve a variety of physical and biological functions including wildlife habitat (waterfowl, big game, furbearers, etc.); fish breeding and foraging habitat; nutrient/sediment trapping; flood control; and recreation. The amount of wetlands has increased on the Snake River from less than 10 acres (4.0 hectares) in 1958 to over 350 acres (141.6 hectares) today (Corps, 1999). In the McNary reservoir, there are over 1,010 acres (408.7 hectares) of wetlands (Corps, 1992).

Wetlands along the lower Snake River reservoirs are characterized by emergent plant communities. Cattails (Typhus latifola) and bulrush (Scirpus sp.) are the predominant wetland plants along the reservoirs.

Wetlands associated with the McNary reservoir are also of the emergent variety. Extensive wetlands occur in the McNary reservoir near the mouths of the Walla Walla, Snake, and Yakima Rivers. Typical native vegetation includes cattails, bulrush, willows, and black cottonwood. Exotic species include purple loosestrife and false indigo.

On the Snake River, numerous small pockets of wetlands and ponds exist in small impoundments behind roads and railroads along the reservoirs and other embayments. Vegetation is dominated by cattails and softstem bulrush, with some rushes and sedges. Purple loosestrife and false indigo are found in these areas. The increase in these types of communities is due to several factors: (1) abundant slack water, which causes sediments carried into reservoirs to accumulate and create good conditions for wetland vegetation development; (2) several embayments and backwaters that allow for wetland development; (3) drawdowns that allowed wetland vegetation to establish; and (4) runoff and seeps from nearby irrigated HMUs (Corps, 1999).

3.2.1.3 The HMUs

The HMUs are lands designated primarily for management as wildlife habitat. These areas provide essential habitat for numerous plants and wildlife of the lower Columbia/Snake River system and have been developed or have established naturally under prolonged periods of normal reservoir conditions. Sixty-two HMUs have been designated along the lower Snake River (Corps, 1999). Approximately 760 acres (307.6 hectares) of irrigated lands are associated with the 11 intensively managed (i.e., irrigated) HMUs on the four lower Snake River projects (Sather-Blair et al., 1991). The largest HMU, Big Flat at 850 acres (344.0 hectares) (Sather-Blair et al., 1991), is located 3 miles (4.8 km) upstream of Ice Harbor Dam. Irrigated HMUs at each of the reservoirs have been planted extens ively with trees and shrubs along reservoir shorelines and with herbaceous plants to establish feeding areas for wildlife.

Numerous dryland (non- irrigated) HMUs are located along each of the lower Snake River reservoirs. Dryland HMUs have limited development that may include guzzlers (water-trapping structure for wildlife), quail roosts, and brush piles. The Joso site is a dryland HMU encompassing about 568 acres (229.9 hectares). The center of this HMU is a large gravel quarry that was excavated during the relocation of the railroads prior to the filling of Lower Monumental reservoir. The habitat surrounding the gravel quarry is shrub-steppe. Four guzzlers and two brush piles have been constructed on the HMU.

McNary reservoir has several wildlife management areas. Five HMUs, totaling 4,500 acres (1 821.1 hectares), are managed by the Corps and USFWS. The 500-acre (202.3-hectare) McNary Wildlife Nature Area is located just downstream of McNary Dam and is also managed by the Corps. The 3,600-acre (1 456.9-hectare) McNary National Wildlife Refuge (NWR) is managed by the USFWS near the confluence of the Snake and Columbia Rivers. This refuge has recently been expanded to include the Corps-owned lands (mentioned above) under lease to the USFWS.

3.2.2 Wildlife

The project reservoirs provide essential habitat for numerous birds, reptiles, amphibians, small mammals, bats, and big game animals (Asherin and Claar, 1976, Tabor, 1976). Asherin and Claar (1976) identified 87 species of mammals and 257 species of birds that occur in the vicinity of the lower Snake River and McNary reservoirs. They generally are dependent on tree-shrub riparian habitat associated with the project reservoirs (Lewke and Buss, 1977). In general, riparian and wetland areas support higher population densities and species numbers than dryland shrub-steppe, talus, cliff, and/or grassland habitat, which are also prevalent along the project reservoirs. Habitats associated with the river generally support trees or dense grass- forb cover that provide more structurally complex areas and more abundant forage resources than adjacent uplands.

Inundation of the lower Snake and Mid-Columbia Rivers following dam construction between the early 1950's and 1975 eliminated nearly all of the woody riparian habitat present. Since inundation, the shorelines with adequate hydrology have reestablished a portion of this riparian community. Due to the lack of suitable hydrology and land management practices of the time, the riparian habitat is now highly discontinuous and dominated by exotic species such as Russian olive. Additional riparian habitats have been developed through the establishment of intensive HMUs. Thus, wildlife generally associated with wildlife habitats tends to be concentrated in these HMUs and in the natural vegetation along the major tributaries, such as the Tucannon, Palouse, and Walla Walla Rivers.

The project reservoirs provide food, water, and cover for numerous wildlife species and are especially important in the Clearwater River, lower Snake River, and McNary reservoir where moisture is extremely limited. Wildlife that typically uses riparian and wetland habitat area associated with the project areas can be divided into nine main groups: waterfowl, upland game birds, raptors, small mammals, other non- game birds, big game animals, furbearers, amphibians and reptiles, and listed threatened and endangered species (Asherin and Claar, 1976; Tabor, 1976).

3.2.2.1 Waterfowl

Over 30 species of waterfowl have been documented to occur on the Columbia and Snake Rivers in the project area (Lewke and Buss, 1977: Asherin and Claar, 1976; Rocklage and Ratti, 1998). Resident, breeding waterfowl numbers are generally low except for Canada geese (Branta canadensis), mallard (Anas platyrhynchos), Barrow's goldeneye (Bucephala islandica), and American widgeon (Anas americana), which occur throughout the projects. Waterfowl nesting is limited within the lower Snake River reservoirs because of shortage of suitable nesting habitat. Nesting habitat is more readily available adjacent to the McNary reservoir.

Of the four lower Snake River reservoirs, Ice Harbor reservoir typically has the most waterfowl (mainly mallard and Canada geese) during migration and winter with a high count of almost 16,000 mallards in December, 1978 (unpublished aerial waterfowl counts by the USFWS and WDFW). This may be a result of the Ice Harbor reservoir being a waterfowl reserve where waterfowl hunting is prohibited. While waterfowl numbers drop off upstream, the diversity of waterfowl increases (USFWS, 1999a).

The McNary reservoir supports a large population of nesting Canada geese. The 25-plus islands, together with the McNary NWR and HMUs, annually produce up to 600 to 700 goslings and provide habitat for nesting ducks, primarily mallards. Most goose nesting occurs on seven islands, with the greatest numbers of successful goose nests on Badger Island.

Canada goose nesting on the lower Snake River and in McNary reservoirs occurs primarily on reservoir islands and along cliffs. Surveys conducted between 1974 and 1987 in the project vicinity have found that over 80 percent of Canada goose production was supported on Badger, Foundation, and New York Islands, producing 280 nests (Boe, 1988). Island nesting on the lower Snake River produced about 125 nests in 1996 (Corps, 1999).

3.2.2.2 Game Birds

The major game bird species occurring in the study area include ring- necked pheasant, California quail, chukar, and mourning dove of which only the mourning dove is native (Asherin and Claar, 1976; Rocklage and Ratti, 1998). These game birds are relatively common throughout the study area, extending from riverside to the upland areas.

Ring-necked pheasants depend on permanent shrub and tall herbaceous cover that is maintained on irrigated lands in the study area. They are often found on irrigated HMUs foraging on food plots (Corps, 1999).

Chukars use a wide variety of habitats. Oelklaus (1976) found that chukars use Douglas hackberry, smooth sumac, and poison ivy stands along the project area. Shrub and talus areas are important for nesting (USFWS, 1995). Cheatgrass and agricultural grains are important for foraging (Gilbreath and Moreland, 1953; Christensen, 1970).

Of all the game species inhabiting the project area, California quail were most adversely affected by inundation of the dams. Pre-project habitat conditions were ideal for California quail (Sather-Blair et al., 1991) with good interspersion of cropland (food) and riparian vegetation that provided important escape and winter cover. Since completion of the projects, the percentage of project area in food-producing cover types (e.g., agricultural crops) has decreased, and the distances between food and cover have increased.

3.2.2.3 Raptors

Riparian forests and wetlands along the Snake, Columbia, and Clearwater rivers provide perching and nesting opportunities, and concentrated prey (e.g., small mammals, songbirds) (Tabor, 1976; Asherin and Claar, 1976; Asherin and Orme, 1978). In general, cliffs and large trees along riverbanks typically support diverse raptor populations. The McNary and lower Snake River reservoirs provide cliff areas in proximity to the rivers that may provide potential nest and roost sites for bald eagles (Haliaeetus leucocephalus), golden eagles (Aquila chrysaetos), and prairie falcons (Falco mexicanus) (Payne et al., 1975; Asherin and Claar, 1976; Tabor, 1976).

Rocklage and Ratti (1998) documented 17 species of raptors in the study area. Asherin and Claar (1976) found only 13 species within the same area, with one species (burrowing owl) not seen in the previous study. During the summer of 1981, Fleming (1981) found a total of 172 raptor nests of 10 species along the Snake River from Lewiston, Idaho, to Ice Harbor. Although nesting information was not specifically recorded, Rocklage and Ratti (1998) recorded 209 raptors of 12 species present along the lower Snake River during the breeding season. Asherin and Claar (1976) found American kestrel (Falco sparverius) and red-tailed hawk (Buteo jamaicensis) to be the most common raptors in the lower Snake River area.

Peregrine falcons (Falco peregrinus) were recently removed from the endangered species list. There are no reported peregrine falcon nests in or near the dredging or dredged material disposal sites. An active aerie is located along Weissenfels Ridge near the confluence of the Snake River and Tenmile Creek, approximately 8 miles (12.9 km) south of Clarkston (USFWS, 1999a). Peregrine falcons could potentially travel through this area during migrations.

Bald eagles are found in the study area usually during the winter, between November and March. A few bald eagles winter along the McNary reservoir (BPA et al., 1994). Mid-winter bald eagle surveys reported 10 eagles on the lower Snake River (Corps, 1999). One nesting attempt was recorded on the Strawberry Islands, near the mouth of the Snake River in 2000. This nest was unsuccessful. Eagles feed primarily on waterfowl and fish, which are present in the reservoirs. Bald eagles are discussed further in section 3.3.2.1.

3.2.2.4 Non-Game Birds

The project reservoirs provide essential habitat for numerous colonial nesting birds, shorebirds and songbirds (Asherin and Claar, 1976, Tabor, 1976). They generally are dependent on tree-shrub riparian habitat associated with the project reservoirs (Lewke and Buss, 1977). In general, riparian and wetland areas support higher population densities and species numbers than dryland shrub-steppe, talus, cliff, and/or grassland habitat, which are also prevalent along the project reservoirs. Habitats associated with the river generally support trees or dense grass-forb cover that provides more structurally complex areas and more abundant forage resources than adjacent uplands.

There is some evidence that bird species richness along the project area has declined from pre-impoundment conditions. Of 61 total bird species found by Dumas (1950), 12 were not reported by a more recent study (Rocklage and Ratti, 1998). These species include the black-chinned hummingbird, veery, red-eyed vireo, solitary vireo, American redstart, Brewer's blackbird, and fox sparrow. Most of these species are associated with riparian forest habitat (Smith et al., 1997). These species are still seen in and around the lower Snake River by the local chapters of the Audubon Society. The redstart, vireos and brewers blackbird are seen very rarely and may have been migrants in previous studies. It has been documented that conversion of native riparian forest to exotic species such as Russian olive, have reduced species diversity in the region, especially for insectivorous birds (USFWS, 1997).

Rocklage and Ratti (1998) observed a total of 92 bird species during the breeding season within the study area. Within the various habitats along the rivers, the HMUs had higher bird species richness during both the breeding season and the fall than the woody drainages leading into the reservoirs. Their narrow width and their degradation may limit the suitability of the woody drainages for foraging and nesting. Therefore, despite the lack of mature riparian habitat on the HMUs, they still provide important habitat for riparian bird species.

California gulls (Larus atricilla), ring-billed gulls (L. delawarensis), Forster's terns (Sterna forsteri), Caspian terns (S. caspia), and double crested cormorants (Phalacrocorax auritus) nest in large concentrations on the lower Columbia River, particularly on Crescent and Foundation Islands along the McNary reservoir. Pied-billed grebes (Podilymbus podiceps) and rail species use many of the backwater areas throughout the project area. Killdeer (Charadrius vociferus) and spotted sandpiper (Actitis macularia) nest and forage just upslope from the high reservoir line and along the shoreline throughout the project area. In addition, over 1,000 white pelicans (Pelicanus erythrorhynchos) typically occur along the Columbia River between Boardman, Oregon, to Vernita Bridge, north of Richland, Washington (Corps, 1992).

3.2.2.5 Small Mammals

Eleven small mammal species have been observed in the study area, with two additional species likely present (Corps, 1999). These species include deer mouse, western harvest mouse, Great Basin pocket mouse, house mouse, long-tailed vole, montane vole, northern pocket gopher, vagrant shrew, Merriam's shrew, bushy-tailed woodrat, and Ord's kangaroo rat (Rocklage and Ratti, 1998; Johnson and Cassidy, 1997; Asherin and Claar, 1976). Deer mice make up the majority of individuals found in the project area. Rocklage and Ratti (1998) found six species, with deer mouse composing 74 percent of total captures. Notably, some evidence suggests that small mammals prefer native riparian habitat to other habitat. Asherin and Claar (1976) found the highest species diversity in their study in the native cattail and shrub willow habitat types. Six species of bats have been documented in the study area and five more are suspected to occur based on habitat suitability, their range, and their occurrence in the vicinity (Johnson and Cassidy, 1997; Mack et al., 1994; Asherin and Claar, 1976). Documented species include Yuma myotis, western pipistrelle, pallid bat, small- footed myotis, California myotis, and Townsend's big-eared bat (Asherin and Claar, 1976; Johnson and Cassidy, 1997). Other species of bats that may also be present include long- legged myotis; long-eared myotis; fringed myotis; hoary bat, and big brown bat (Johnson and Cassidy, 1997; Asherin and Claar, 1976).

3.2.2.6 Furbearers

Aquatic furbearers occur in each of the project reservoirs and include muskrat (Ondatra zibethicus), beaver (Castor canadensis), river otter (Lutra canadensis), and mink (Mustela vison). In general, this group is dependent on riverine areas, embayments, ponds, tributaries, and riparian forests for den sites and foraging areas. Beaver distribution within the project reservoirs is strongly associated with the presence of cottonwood and protected areas. (Asherin and Claar, 1976). Muskrats are particularly abundant in embayments and sloughs where aquatic plants are also abundant. Mink and river otter use the project reservoirs, ponds, sloughs, and backwater areas for foraging and denning. Both the mink and river otter use riprap areas along the banks as den sites (Sather-Blair et al., 1991).

Asherin and Claar (1976) observed four species of terrestrial furbearers: bobcat, coyote, raccoon, and striped skunk and the three species of aquatic furbearers discussed above. They concluded that aquatic furbearer abundance was low along the lower Snake River. Asherin and Claar (1976) also noted that that the aquatic furbearers were more abundant in those study segments with more extensive riparian habitat such as the McNary NWR.

Although it is likely that some of these species were never abundant (Asherin and Claar, 1976), inundation by the reservoirs probably eliminated much of the riparian habitat that was important for foraging and denning for many of the furbearers. In particular, muskrat and mink seem to have declined (WDG, 1984; Corps, 1999). When comparing habitat value for river otter both pre-project, lower Snake River, and conditions today, habitat values meet or exceed those values for pre-project conditions. This is mainly due to the shoreline structure developed by riprap and woody exotic vegetation. It is not clear whether this has translated into higher otter numbers since surveys for otters have not been conducted in recent years.

3.2.2.7 Big Game Mammals

Mule and whitetail deer are the most common big game inhabiting the study area (Tabor, 1976). Mule deer make up about 80 percent of the deer population with the whitetail deer making up the remaining 20 percent. Populations of deer have recovered to pre-impoundment carrying capacity (Corps, 1990). This increase is at least partly due to the development of habitat in HMUs and the exclusion of livestock from much of the study area (Corps, 1999).

Suitable habitat for deer in the study area mainly serves as wintering range, with the deer making seasonal and daily migrations out of the canyons to forage in the surrounding cultivated land. Deer use a wide variety of habitats including shrub and brush for cover and fawning and grassland for foraging.

Mule deer are found in increasing numbers from the Lower Monumental reservoir upstream to the upper half of the Little Goose reservoir (Tabor, 1976). There is some evidence that greater precipitation and higher habitat diversity along the upper two lower Snake River reservoirs provide more stability for deer populations than habitats downstream and extending into the McNary reservoir (Corps, 1990).

Other species that have been observed along the river but that are considered uncommon include elk, bighorn sheep, black bear, moose, and mountain lion (Corps, 1999).

3.2.2.8 Amphibians and Reptiles

Sixteen species of amphibians and reptiles have been documented in the study area (Asherin and Claar, 1976; Loper and Lohmann, 1998; McKern, 1976). The most commonly occurring species were the Pacific tree frog (Hyla regilla), bullfrog (Rana catesbeiana), western yellow-bellied racer (Coluber constrictor mormon), Great Basin gopher snake (Pituophis melanoleucus deserticola), long-toed salamander (Ambystoma macrodactylum), western toad (Bufo boreas), night snake (Hypsiglena torquata), western rattlesnake (Crotalus viridis), and painted turtles (Chrysemys picta). Other species that may occur within the study area, but were not observed by Asherin and Claar (1976) or Loper and Lohmann (1998) include: the tiger salamander (Ambystoma tigrinum), northern leopard frog (Rana pipiens), short-horned lizard (Phrynosoma douglassi), sagebrush lizard (Sceloporus occidentalis), rubber boa (Charina bottae), and the ringneck snake (Diadophis punctatus).

Of the vegetation types sampled by Asherin and Claar (1976), the ones most closely associated with water had the greatest relative abundance of amphibians. In particular, native willow and emergent wetland habitats have the greatest species diversity. In general Loper and Lohmann (1998) found that species richness and abundance were low at both riparian and upland locations. Some of the reasons may include the relatively young age of the recovering riparian fringe beside the existing reservoirs; the isolation of suitable riparian habitat into discrete patches along the river (i.e., HMUs); and fluctuating water levels in the reservoirs that prevent the consistent occurrence of litter, debris, pools, and vegetation that these species could use for breeding, resting, and forage (Loper and Lohmann, 1998).

3.3 ENDANGERED SPECIES

The ESA establishes a national program for the conservation of threatened and endangered species of fish, wildlife, and plants and the preservation of the ecosystems on which they rely. Section 7 of the ESA requires Federal agencies to consult with the USFWS and/or NMFS as necessary to ensure that their actions are not likely to jeopardize the continued existence of endangered or threatened species or adversely modify or destroy critical habitat. It also requires that Federal agencies prepare BA's of the potential effects of major construction actions on listed species.

Several species listed as threatened or endangered under the ESA are potentially found in the lower Snake River reservoirs and McNary reservoir. The following sections describe these species and their use of the study area. Additional information regarding the presence of these species in the study area and the impacts of the proposed dredging and dredged material disposal are found in the BA's (appendix F and appendix G) prepared by the Corps. Full documentation of these consultations is presented in Appendix F (for NMFS) and Appendix G (for USFWS).

3.3.1 Fish

3.3.1.1 Anadromous Fish

The existing anadromous fish species and environmental conditions in the study area that could be affected by the alternatives in this DMMP/EIS are discussed in detail in section 3.1.1.1. However, the NMFS has determined that the effects of the proposed actions will not jeopardize the continued existence of endangered SR sockeye, threatened SRF chinook, threatened SRSS chinook, threatened SRB steelhead, endangered UCRS chinook, endangered UCR steelhead, or threatened MCR steelhead or result in the adverse modification or destruction of their Critical Habitat. The determination of no jeopardy is based upon the current status of the species, the environmental baseline for the action area, and the effects of the proposed actions. Other potentially impacted species such as Pacific lamprey are also discussed in section 3.1.1.1.5.

3.3.1.2 Resident Fish

The only subpopulations of bull trout associated with the four lower Snake River reservoirs spawn and rear in the Tucannon River Basin. Both resident and migratory forms occur there. A detailed discussion on bull trout is presented in section 3.1.1.2.3. Margined Sculpin is a species of concern and is discussed in section 3.1.1.2.5.

3.3.2 Wildlife

There is one listed wildlife species that may occur in the project area (USFWS, 2000), the bald eagle. Washington ground squirrel is currently a candidate species for listing. In addition to the listed species, a discussion of species of concern is presented in section 3.3.4.

3.3.2.1 Bald Eagle - Threatened

Bald eagles are usually associated with a source of permanent water, such as reservoirs, lakes and free-flowing rivers, with abundant fish and nearby sites for perching, roosting, and, in season, nesting. Their primary prey is fish, especially salmon, but they also eat small mammals, various water birds, such as waterfowl, and carrion. In the winter, provided the roosting sites and food are abundant, eagles roost in groups, particularly in conifer stands or along rivers with migrating salmon.

In the western United States, eagles reside along the western coast from southern Alaska through the Pacific Northwest to northern California. In the winter, bald eagles can be found throughout most of the United States west of the Mississippi River. In Washington, bald eagles nest along the Pacific Ocean, Puget Sound, large lakes, and rivers. They winter along rivers that support large runs of anadromous fish, the Puget Sound, and the Pacific Ocean.

During the nesting season (February 1 through August 15), bald eagles use breeding habitat close to rivers, lakes, marshes, or other food sources. Important habitat components include nest trees, perch trees, and available prey. Live, mature trees with deformed tops are often selected for nesting, and nests are often reused year after year. Snags, trees with exposed lateral branches, or trees with dead tops are important for perch-sites while hunting or defending territories. Perches used for foraging are normally close to water where fish, waterfowl, seabirds, and other prey can be captured.

Wintering bald eagles (November 1 through March 15) congregate along rivers, lakes, and streams, where winter runs of salmon provide an abundant prey base. Waterfowl concentrations may also be important winter food sources. In eastern Washington, mixed stands of black locust and black cottonwood provide important roosting and perching habitat.

There are no documented successful bald eagle nests in or around the project area. An unsuccessful nesting attempt occurred on Strawberry Island near the mouth of the Snake River during the 2000 nesting season. This site is adjacent to proposed dredging activity for the approach to Ice Harbor. Bald eagles have also attempted nesting in the Clearwater and Grande Ronde drainages and at the Hanford Reservation north of Richland, Washington. These sites are well over a mile (1.6 km) from the project area. The limited amount of suitable habitat makes additional nesting in the project area unlikely.

Based on data from Corps mid-winter surveys, bald eagles may be present in the project area during the winter, roosting in black locust or black cottonwood trees where available. Mid-winter censuses have been conducted on the lower Snake and Columbia Rivers from McNary (on the Columbia below the confluence with the Snake) to Asotin, Washington, [2 miles (3.2 km) upriver from Clarkston, Washington] annually since 1989. These surveys generally take place in January and are divided into two survey areas. The Western Project survey area extends from McNary to Lower Monumental. The Eastern Project area extends from Lower Monumental to the upper influence of the Lower Granite reservoir, near Asotin, Washington. Surveys were typically conducted in January and were confined to Corps- managed lands along the rivers.

The last 5 years of survey results were examined to determine average annual bald eagle occurrence. In the Western Project area, bald eagle counts ranged from 11 to 19 individual birds annually. Many of the locations are less than 1 mile (1.6 km) from proposed dredging and dredge disposal activities. These include Strawberry Island below Ice Harbor, Sacajawea Park at the Snake and Columbia Rivers confluence, and Big Flat HMU above Ice Harbor. In the Eastern Project area, between three and five individual bald eagles per year have been counted. One or two of these are usually found in the Snake/Clearwater Rivers confluence area, near the proposed Lower Granite dredging and levee-raising activities.

3.3.2.2 Washington Ground Squirrel - Candidate

These squirrels are found in steppe and open shrub-steppe, where they prefer deep, loose soil for digging burrows. One existing colony in Walla Walla County is within the study area, while five additional colonies are located nearby. Use of the Joso site for upland disposal of dredged material has the potential to negatively impact Washington ground squirrels during disposal operations through disturbance of habitat. Most of the ground to be disturbed is within the gravel pit, where soils are less suitable for ground squirrels. Most suitable habitat will remain undisturbed. Re storation of grassland habitat after disposal may benefit ground squirrels.

3.3.3 Plants

One plant species with Federal status may potentially occur in the project area: Ute ladies' tresses. Also, Spalding's silene is proposed to be listed and White Bluffs bladder-pod is a candidate for listing.

3.3.3.1 Ute Ladies' Tresses (Spiranthes diluvialis) - Threatened

This orchid is a lowland species, typically occurring beside or near moderate gradient, medium to large streams and rivers in the transition zone between mountains and plains. It is not found in steep mountainous parts of the watershed nor along slow meandering streams out in the flats. The communities where it is often found tend to be typical of riparian habitat in the area. The species tend to occupy graminoid (grasses, rushes, and sedges) dominated openings in shrubby areas. It occasionally occurs in spring- fed wetlands in broad valleys isolated from watercourses. Soil moisture must be at or near the surface throughout the growing season. The species tolerates periodic flooding, but does not occupy constantly inundated areas (USFWS, 1998).

Ute ladies' tresses occur in a variety of settings, including floodplains, moist to wet meadows on floodplains, abandoned meander channels, moist to wet meadows irrigated by freshwater springs, riparian streambanks, borrow pits, upper edges of riverbanks, islands, point bars, and various topographic positions up to 200 feet (61.0 m) horizontally and 0.5 to 4 feet (0.2 to 1.2 m) vertically from the water's edge, but not on steep slopes (USFWS, 1998).

Ute ladies' tresses were discovered in northern Washington (the Okanogan River valley) for the first time in 1997. They were also found in the Snake River Basin in southeastern Idaho in 1996. It is now known to be present in northern Washington, southern Idaho, and nearby parts of Montana. The USFWS has determined that, in the absence of adequate surveys, this species may be expected to occur in suitable habitat throughout Idaho and Washington (USFWS, 1998).

3.3.3.2 Water howellia (Howellia aquatilis) - Threatened

howellia grows in firm consolidated clay and organic sediments that occur in wetlands associated with ephemeral glacial pothole ponds and former river oxbows (Shelly and Moseley, 1988; Lesica, 1992). These wetland habitats are filled by spring rains and snowmelt run-off; and depending on temperature and prescription, exhibit some drying during the growing season. This plant's microhabitats include shallow water, and the edges of deep ponds tha t are partially surrounded by deciduous trees (Shelly and Moseley, 1988; Gamon, 1992).

Only 79 small populations of this aquatic plant were known to exist when the proposed rule to list the species was published (58 FR 19795). Subsequent inventories cond ucted for howellia in the State of Washington located 28 new sites in Spokane County alone, thus expanding the number of known populations to 107 (Roe and Shelly, 1992; N. Curry, in Litt., 1993; J. Gamon, Washington Natural Heritage Program in litt., 1993; R. Moseley, Idaho Conservation Data Center, in Litt., 1993). howellia appears to be extirpated from California and Oregon, from Mason and Thurston Counties in Washington, and Kootenai County in Idaho (Jokerst, 1980; Shelly and Moseley, 1988; Oregon Natural Heritage Program, 1991; Gamon, 1992).

Nearly all of the remaining populations of howellia are clustered in two main population centers or metapopulations. Within these areas, individual populations occur primarily in clusters of closely adjacent ponds, although some ponds within the range of these metapopulations are unoccupied. One metapopulation near Spokane, Washington, consists of 46 individual populations in Spokane County, Washington, and one in Latah County, Idaho. A second metapopulation is found in the drainage of the swam river in northwestern Montana (Lake and Missoula Counties, where 59 individual populations are found. In addition to metapopulations, a third site near Vancouver in southwestern Washington (Clark County) contains two populations that are in close proximity of each other (Gamon, 1992).

Water howellia is not documented in Idaho near the study area (Idaho Conservation Data Center, 2000). The study area itself does not exhibit any habitat which could be used by this species.

3.3.3.3 Spalding's Silene - Proposed

Spalding's silene is a plant that has white flowers and is found in virgin Idaho fescue (Festuca idahoensis) habitat types in the Palouse region (Washington Natural Heritage Program, 1981). Although not documented within the study area, this species has been found in Whitman and Asotin counties.

3.3.3.4 White Bluffs Bladder-pod - Candidate

A perennial, grayish-pubescent herb of the mustard family that has a well-developed taproot, a dense, many- leaved rosette of gradually reduced leaves, and dense inflorescences of yellow flowers.

This narrow endemic species is restricted to a very small area in Franklin County adjacent to the Columbia River in south-central Washington. It is currently known from an area of a few yards (meters) wide by approximately 10 miles (17 km) long.

The species is restricted to a very small area along the Columbia River in shrub steppe vegetation. The species is restricted to dry, barren, nearly vertical exposures of calcium carbonate paleosol (a "caliche" soil). The substrate is extremely alkaline and highly calcareous. Elevation ranges between 780 and 890 feet. Associated species include big sagebrush, buckwheat milkvetch, slender buckwheat, Snake River cryptantha, and Sandberg's bluegrass. The range of this species is within the driest region in the state of Washington; the general area receives an average of about 6 inches (15.2 cm) of precipitation per year. As a result, the overall cover of vegetation is extremely low. As noted above, the species is restricted to a highly alkaline substrate that most plants find inhospitable. The species is presumably reliant on periodic exposure of these substrates.

3.3.4 Species of Concern

The following discussion is cited from appendix G, Biological Assessment for Non-Anadromous Fish and Terrestrial Species.

3.3.4.1 Wildlife

3.3.4.1.1 Black Tern

Black terns are small terns that eat primarily insects and can occur statewide, in or near wetlands and sloughs. They usually nest in marshy wetlands in June. Black terns are periodically reported by birders in the project area, primarily at the mouth of the Walla Walla River, and are believed to use the area only during migration (Ackerman, 2001). The project is unlikely to impact black terns.

3.3.4.1.2 California Floater

California floaters are mussels found in unpolluted fresh water, except in small creeks. They prefer lakes and slow streams with areas less than 6.6 feet (2 m) deep and sandy bottoms. Adults will also live on mud bottoms. Juveniles are parasitic on gills, fins, and barbels of host fish. The California floater have been located upstream of Hells Canyon Dam (Idaho Dept. of Fish and Game, Conservation Database Center GIS Database). Dorband (1980) indicated that this genus was not found in Lower Granite Reservoir in 1977. It is unlikely this species would occur in the study area.

3.3.4.1.3 Columbia Pebblesnail

Columbia pebblesnails are found in the main channels and free- flowing parts of rivers including the Columbia, Grande Ronde, Salmon, and Snake Rivers. More recent documentation indicates they are present just above the study area on the lower Snake River. They are often common at the edges of rapids or immediately downstream of whitewater areas, and they feed on diatoms and algae. The Columbia pebblesnail have been located upstream of the study area in the Lower Salmon River by Idaho Conservation Database personnel. Dorband (1980) did not list the genus of this species as present in the Lower Granite Reservoir in 1977. Since this species has been found in a direct tributary of the Snake River above Lower Granite Reservoir, it is possible a few individuals could migrate downstream of that point. Water quality would still be a limiting factor, so it would be unlikely to find this species in the impounded areas of the lower Snake River, so should not be found in the study area.

3.3.4.1.4 Columbia Spotted Frog

Columbia spotted frogs are found in warmwater marshes, overflow wetlands, and bogs with non-woody wetland vegetation. They are found scattered across most of eastern Washington although they have not been observed in the study area (Ackerman, 2001; Loper and Lohman, 1998).

3.3.4.1.5 Ferruginous Hawk

These large hawks prefer open plains and brushy open country and avoid forested areas. They nest in trees along streams, bluffs, rock piles, and artificial structures. Ferruginous hawks feed primarily on ground squirrels, rabbits, and other small mammals. They are uncommon along the lower Snake River corridor although some suitable nesting habitat may be present.

3.3.4.1.6 Fringed Myotis, Long-Eared Myotis, Long-Legged Myotis, Pale Towns end's Big-Eared Bat,

They commonly forage near or over water and roost in trees and shrubs (riparian areas along the lower Snake River), rock crevices, and buildings. However, the small- footed myotis forages along cliffs, rock outcrops, and dry canyons.

Depending on the size of interstitial spaces, bats may use riprap areas for roosting or hibernating (Anderson, 2001).

3.3.4.1.7 Harlequin Duck

Harlequin ducks generally rely on fast, turbulent mountain streams as breeding habitat. They may be present in the study area in August and September (following the nesting season) although sightings are rare. They winter in coastal areas and, thus, would not likely be present during the project work window of December 1 through March 31.

3.3.4.1.8 Little Willow Flycatcher

The little willow flycatcher uses open brushy areas, especially scrub-shrub wetlands comprised of willows. Willow flycatchers are seen along riparian drainages in or near the study area during spring and early summer.

3.3.4.1.9 Loggerhead Shrike

Loggerhead shrikes are robin-sized birds that feed mainly on insects, small birds, and mammals. They would be seen in the area during the summer breeding season. Preferred habitat includes shrub-steppe and any semi-open area with shrubs, fences, powerlines, or small trees for perches.

Loggerhead shrikes are currently seen on the Hanford Reservation and adjacent areas during the summer. Most of the study area is outside of this native shrub-steppe habitat.

3.3.4.1.10 Mountain Quail

Mountain quail are uncommon birds that prefer shrubby/forested areas and are found at lower elevations in the Blue Mountains. Mountain Quail have been recorded in the mountainous areas of northwestern Idaho by the Idaho Consevation Database personnel. The study area is primarily degraded shrub-steppe which starts at the foothills of the Idaho mountains and goes into the heart of the Pasco Basin. There is no suitable habitat for this species within the study area.

3.3.4.1.11 Northern Goshawk

Northern goshawks are large hawks that prefer mature and old-growth forests for nesting and would not nest in the study area. Observations of goshawks would likely be during migration and winter. They are aerial hunters, flying between trees and under canopy in search of grouse, smaller birds, and other prey. The northern goshawk is primarily a migrant in the area which has been seen regularly in and around the study area by local chapters of the Audubon Society.

3.3.4.1.12 Northern Sagebrush Lizard

Northern sagebrush lizards are primarily shrub-steppe dwellers, but also use bouldered regions and forested slopes. They are typically ground lizards and rarely climb into shrubs. They prefer fine gravel soils, but are also found on sand y or rocky soil. They need rock crevices, mammal holes, and similar cover for refuge. Northern sagebrush lizards are currently seen on the Hanford Reservation and adjacent areas during the summer. Most of the study area is outside of this native shrub-steppe habitat.

3.3.4.1.13 Olive-Sided Flycatcher

Olive-sided flycatchers are birds that seem to prefer mixed and broken forests with wooded streams and some wetland. Their diet consists entirely of flying insects that they search for from high snags and perches. They nest high in conifer trees. Olive-sided flycatchers are seen along riparian drainages in or near the study area during spring and early summer.

3.3.4.1.14 Western Burrowing Owl

These owls are generally found in open, broken, or flat areas, including shrub-steppe and agricultural areas. They are seen regularly in the Tri-Cities, Hanford, and Yakima Range areas (Ackerman, 2001). Opportunistic feeders, they prey primarily on insects and small mammals, but also on birds, fish, and amphibians when available. They use ground squirrel or other mammal burrows for shelter and nesting.

Artificial burrows were created at the Joso HMU in the early 1980's. No use by burrowing owls has been documented although no formal monitoring plan has been implemented.

3.3.4.2 Plants

3.3.4.2.1 Northwest Raspberry

This is a Snake River endemic that is found in the Snake River canyon and adjacent tributaries. It occurs along drainage bottoms and somewhat moist areas on the adjacent slopes along small tributaries to the Snake River, such as Nisqually John Canyon. It is known from less than two dozen sites, with some of the historic sites inundated with the construction of Lower Granite (Clegg, 1973). Whether it has become established along the current reservoir shorelines is unknown; however, it has become established on at least four of the intensive HMUs (Phillips, 1993).

3.3.4.2.2 Jessica's Aster

This tall perennial species has blue flowers and can be found in association with the northwest raspberry. It is found along streambanks and open places in the Palouse region and is currently known from only nine populations in Whitman County (Washington Natural Heritage Program, 1981). None of these populations are found within the study area.

3.3.4.2.3 Broad-Fruit Mariposa

This very showy species has purple flowers and is found along the borders of seasonally wet meadows (Washington Natural Heritage Program, 1981). Although there is no documented presence within the study area, it has been found in Garfield and Whitman counties.

3.3.4.2.4 McFarlane's Four O'Clock

McFarlane's four o'clock is known to occur in three geographically isolated units occupying approximately 163 acres (65.0 hectares) in Idaho and Oregon. The Snake River unit occupies approximately 25 acres (10.1 hectares) along 6 miles (9.7 km) of Hells Canyon on the banks and canyonland slopes above the river. This plant is found on steep (50 percent) sandy slopes underlain by talus in canyonland corridors where the climate is regionally warm and dry with precipitation occurring mostly in a winter-to-spring period (Robinson, 1996).

There are no reported occurrences of McFarlane's four o'clock in the project vicinity (Robinson, 1996). This project is not expected to impact this species.

3.3.4.2.5 Washington Polemonium

A member of the phlox family, this species has white or creamy flowers and has a characteristic skunk smell. Its habitat includes moist bottomlands and has been found in Whitman County. This species has not been documented in the study area. The species is tied to wet meadow conditions which could be found in the area, so the species may be found if habitat conditions are suitable.

3.4 RECREATION

The lower Snake and Columbia Rivers provide an important recreational resource for the region. There are numerous recreational facilities lining the shores of the lower Snake River reservoirs and McNary reservoir on the Columbia River. Recreational facilities and facility visitation are described in the following sections.

3.4.1 Recreation Facilities and Activities

There are 68 designated recreation sites located on the shores and adjacent areas of the Columbia and Snake Rivers between McNary on the Columbia River and the upstream end of the Lower Granite reservoir on the Snake River. These facilities include wildlife refuges, local and state parks, and marinas, and are managed and operated by the Corps, the USFWS, and local and state recreation agencies. Table 3-1 summarizes the recreation facilities and primary uses. All the facilities are on Corps property.

 

Table 3-1 Recreation Facilities in the Lower Snake River and McNary Reservoirs
Reservoir	Day-Use	Boating	Marina	Camping	State
Lower Granite
Blyton Landing					WA
Chief Looking Glass					WA
Chief Timothy State Park					WA
Chief Timothy Habitat Management Unit					WA
Clearwater Park					ID
Greenbelt Ramp					WA
Gateway Golf Center					WA
Gateway Park					WA
Granite Lake RV Park					WA
Hells Canyon Resort					WA
Hells Gate State Park					ID
Lewiston Levee Parkway					ID
Lower Granite Dam					WA
Nisqually John Landing					WA
North Lewiston Ramp					ID
Offield Landing					WA
Southway Ramp					ID
Swallows Park					WA
Wawawai County Park					WA
Wawawai Landing					WA
Little Goose
Boyer Park and Marina					WA
Central Ferry State Park					WA
Illia Dunes					WA
Illia Landing					WA
Little Goose Dam					WA
Little Goose Landing					WA
Willow Landing					WA
Lower Monumental
Ayer Boat Basin					WA
Devils Bench					WA
Lower Monumental Dam					WA
Lyons Ferry Marina					WA
Lyons Ferry State Park					WA
Riparia Recreation Area					WA
Texas Rapids Recreation Area					WA
Ice Harbor
Big Flat Recreation Area					WA
Charbonneau Recreation Area					WA
Fishhook Park					WA
Hollebeke Park					WA
Ice Harbor Dam Recreation Area					WA
Levey Park					WA
Lost Island					WA
Matthews Recreational Area					WA
Windust Park					WA
McNary
Chiawana Park and Road 54 Park					WA
Columbia Park					WA
Hat Rock State Park					OR
Hood Park					WA
Howard Amon Park					WA
Hover Park					WA
Leslie R. Groves Park					WA
Locust Grove/Martindale					WA
Madame Dorion Memorial Park					WA
McNary Beach Park					OR
McNary Dam Visitor Center					OR/WA
McNary National Wildlife Refuge					WA
McNary Yacht Club					OR
Oregon Boat Launch					OR
Pacific Salmon Visitor Information Center					OR
Pasco Boat Basin					WA
Peninsula Habitat Management Unit					WA
Sacajawea State Park					WA
Sand Station					OR
Spillway Park					OR
Two Rivers Habitat Management					WA
Two Rivers Park					WA
Walla Walla Yacht Club					WA
Wallula Habitat Management Unit					WA
Warehouse Beach					OR
Washington Boat Launch					WA
West Park					OR
Wye Park					WA
Source: Walla Walla District Recreation Pages

Recreational activities take place throughout year, with the highest activity levels during the fair-weather periods of late spring, summer, and early autumn. Due to the setting of recreational facilities, most recreation is related to the water resources presented by the Snake and Columbia Rivers. Boating, swimming, and fishing are common activities, as are camping and day-use activities such as picnicking, hiking, and wildlife observation. Water-dependent activities, such as fishing and boating, take place during the same months that dredging is planned (December through February), however at generally lower activity levels than in spring and summer months, although steelhead fishing activities are highest in the autumn months. Similarly, the riverfront parks in Lewiston are used year-round and could be potentially affected by the alternatives that include raising levees.

3.4.2 Facility Use/Visitation Patterns

As noted in section 3.4.1, recreational facilities in the study area are used for a variety of activities throughout the year. Table 3-2 summarizes annual visitation to all facilities within each reservoir. Visitation reflects both the number of facilities, recreational opportunities, and proximity to large groups of potential users. For instance, because of their proximity to the Tri-Cities (Richland, Pasco, and Kennewick, Washington) area and the number of facilities they offer, the McNary and Ice Harbor reservoirs' recreation facilities have significantly higher levels of visitation than those in the more remote Lower Monumental reservoir.

Regarding the riverfront parks in Clarkston and Lewiston that could be potentially affected by the alternatives including raising the levees, in Fiscal Year 1998 (FY 98) (October 1997 through September 1998) visitation patterns were as follows:

• Swallows Park in Clarkston: 682,200 visitor hours

• Lewiston Levee Park: 329,100 visitor hours

• Chief Looking Glass in Asotin: 69,800 visitor hours

These parks see heavy day use throughout the summer except on very hot days, when the usage is generally in the morning and late evening. Peak usage for all these areas is summer. Spring, fall, and winter receive light to moderate use that is generally weather-dependent (Wiedmeier, 1999). Lewiston Levee Park, for example, features a multi- use trail that runs along the levee, as well as picnic tables and other day use facilities. A levee raise could directly modify the west Lewiston levee.

3.5 CULTURAL RESOURCES

Cultural resources in the DMMP study area (lower Snake River and McNary reservoirs) are a rich source of information about prehistoric and historic human use and occupation of this area dating back over 10,000 years. Cultural resources can generally be placed into one of the following three categories: prehistoric, historic, and traditional cultural properties (TCP). The information provided in this section is primarily derived from the System Operational Review Final Environmental Impact Statement (SOR FEIS) (BPA et al., 1995) and the current information collected in the development of the Lower Snake River Juvenile Salmon Migration FR/EIS. For further information see the Feasibility Study main report and Appendix N, Cultural Resources, as these documents are incorporated by reference.

3.5.1 Cultural Resource Definition

Cultural resources are the material remains of past human life or activities. They can consist of objects, buildings, structures, sites, or districts (a group of closely associated sites). For the DMMP study, the project area or Area of Potential Effect (APE) consists of the four Lower Snake River (Ice Harbor, Lower Monumental, Little Goose, and Lower Granite) and McNary Dams/reservoirs and associated project lands along with those areas affected by proposed dredging and disposal activities. Most of the cultural resources within the APE are prehistoric archaeological sites. Archaeological sites are typically open campsites, housepit villages, rockshelters, rock art (petroglyphs/pictographs), lithic (stone) quarries and workshops, burial grounds and cemeteries, and isolated rock cairns, pits, and alignments. Historic sites are also located in the APE and represent Euro-Am