DATE ISSUED: June 24, 2021
END DATE: July 24, 2021
Interested parties are hereby notified that the Walla Walla District has received an application for a Department of the Army permit for certain work in Waters of the United States, including wetlands, and a request to alter a civil works project, as described below in the attached documents:
APPLICANT: Salmon Whitewater Park Association (SWPA), 195 Highway 93 N, Salmon, Idaho 83467, (208) 756-7002, Breann Green (beejw@hotmail.com).
U.S. ARMY CORPS OF ENGINEERS PROJECT MANAGER: James Joyner, (208) 522-1645 (james.m.joyner@usace.army.mil).
PURPOSE: Provide whitewater park recreational opportunity in the City of Salmon.
WATERWAY: Salmon River
LOCATION: The proposed project would be located on the Salmon River within Section 6, Township 21 North, Range 22 East, near latitude 45.176722º N and longitude –113.899256º W, in Salmon, Lemhi County, Idaho.
DRIVING DIRECTIONS: The proposed project would be located in downtown Salmon near the U.S. Highway 93 Bridge. The project area is in the east channel and a side channel of the Salmon River bounded by Veterans Park to the east and Island Park to the west. Two bridges cross the site: U.S. Highway 93 bridge (highway bridge) and a pedestrian bridge between Veterans Park and Island Park. There is a vehicle bridge from the highway to the park
AUTHORITY: This permit will be issued or denied under the authority of Section 404 of the Clean Water Act (33 U.S.C. 1344). A Department of the Army permit is required for the discharge of dredged or fill material into waters of the United States, including wetlands.
The Corps is also conducting a Section 408 review concurrent with its review under the Clean Water Act. This requirement was established in Section 14 of the Rivers and Harbors Act of 1899, which has since been amended several times and is codified at 33 USC 408 (Section 408). The purpose of a Section 408 review is to ensure that the Congressionally-authorized benefits of a U.S. Army Corps of Engineers project are not undermined by an alteration made by others, and to ensure the alteration is not injurious to the public interest (e.g., flood risk management, coastal storm damage reduction, navigation). In this case, the flood control levee would potentially be impacted by project activities.
WORK: Discharge of approximately 3,786 cubic yards of rock, cement, and sand and excavation of approximately 2,975 cubic yards of native gravel and cobble to facilitate construction of a whitewater park. Specific whitewater park activities include a 1) boulder wave structure, 2) kids play area and fish by-pass channel, 3) levee boulder terracing, 4) boulder deflector above wave structure, 5) inlet channel grading and grade control, 6) pilot channel, 7) random boulder clusters, and 8) bank armoring at island park below the highway bridge. Additionally, a sheet pile cofferdam would be installed to temporarily de-water 5.2 acres (2,520 feet) of river channel to allow construction to occur in the dry. Fill types and volumes below the ordinary high water mark (OHWM) of the Salmon River are shown in the Table below (see Additional Information).
- Boulder Wave Structure - The grouted boulder wave structure and the play area will be constructed first to facilitate the concrete curing. The east channel streambed will be excavated for the wave structure and a downstream grouted pool (Excavation Area 2) (Design Sheets WW-0.2, 2.0). The wave structure will span the channel with a lower notch near the center of the channel. This would focus flows near the center of the channel creating a stronger current near the center and in general more turbulent water across the channel.
The wave structure grading and the crest and exit cross sectional profiles are in Design Sheets 4.1-4.3.
Details of the grouted boulder cut-off wall and the sub-grade for the wave structure are in Design Sheets WW-6.0 and 6.1.
The wave structure low flow profile and the wing structure profile are shown in Design Sheets WW-6.1
The wave structure will consist of 3-foot-plus diameter, rounded boulders bedded with clean gravel and cobble and grouted in with 3500 psi concrete mix. The bedding material will either be well graded 3 to 4-inch clean cobble, or approved native alluvium will be placed to a depth no greater than 12-inches on top of the filter fabric, prior to the placement of boulders to prevent tearing or ripping of the fabric.
The concrete will be cured in the dewatered channel; no uncured concrete will contact flowing water. The concrete will be non-caustic when the surface is “dry” and stiff, usually within a couple hours depending on air temperature (N. Werner, S2O project engineer). However, it will be kept dry for at least 24 hours to protect water quality. Concrete takes a long time to cure; it is assumed to be full strength at 28 days. Ideal conditions occur when the concrete is hydrated or submerged.
Concrete pours will not be conducted during or before anticipated storm events.
All excess concrete and concrete washout slurries from the concrete mixer trucks and chutes will be discharged off-site, or temporarily stored in a washout area designated in an upland area without vegetation and completely isolated from stormwater and drainage. A concrete washout basin lined with ≥10 mm plastic sheeting or geomembrane is required to store excess concrete. The concrete washout basin specifications are shown in Design Sheet WW-8.0. All concrete residues will be hauled off-site and disposed of where it will not contact flowing or standing water.
The upper 1.5 feet of riverbed material excavated during construction will be stored separately from other excavated materials to be tracked into voids and interstitial spaces in the bed armoring during the clean-up and removal from river phase. Sediment barriers will be used to contain this stockpiled material.
- Kids Play Area and Fish By-Pass Channel - The excavator will cut a 10-foot-wide swath through the woody riparian vegetation to excavate the side-channel for a play area and fish by-pass channel (Design Sheets WW-0.2, 0.4, 2.0). The fish by-pass channel dimensions will be approximately 1-foot deep by 10-feet wide at the top, down to 4-feet deep at the outlet (Design Sheets WW-6.3).
Two 3 to 4-foot-deep pools will be excavated in the play area: one above and one below the wave structure (Design Sheets WW-2.0, 6.3). Clean, coarse sand ¼-inch-minus (37 CY) will be added to the pool areas to provide soft footing for the children.
The play area’s 5:1 side slopes will be terraced with 2 to 3-foot diameter, rounded or angular boulders to provide easy access to the play area pools (Design Sheets WW-6.3). A total of 145 CY of boulders will be placed below OHWM.
Another 1,500 ft2 area in the depositional bar between the play area and east channel will be over-excavated to create an eddy. The eddy will provide lower velocity access to the river. It will also encourage sediment deposition to create a natural beach area downstream of the wave structure. The deposition will be a dynamic process. Some years sand will be deposited, other times it will wash out and the beach will be more cobbly.
- Levee Boulder Terracing - A terraced public viewing area measuring 310-feet long and 14 to 15-feet high will be built on the levee between the pedestrian bridge and the highway bridge with 3-foot diameter angular or square boulders (Design Sheets WW-0.2, 0.4, 2.0). This viewing area will be accessible to the public through Veterans’ Memorial Park. The current east channel width will be maintained.
The 5:1 terraced slope profile is shown in Design Sheet WW-6.3). The total volume of rock fill below OHWM will be 1,450 CY.
- Boulder Deflector Above Wave Structure - A deflector of 3-foot-plus diameter, rounded boulders will be built into the levee, upstream of the pedestrian bridge (Design Sheets WW-0.2 and 2.0). The deflector will direct flow to maintain the pilot channel depth to the crest of the wave structure. The deflector will have 150 CY of boulders below OHWM.
- Inlet Channel Grading and Grade Control Structure - An excavator will be used to remove a portion of the depositional bar at the top of the east channel that has continued to aggrade since the 2017 flood. Approximately 165 CY of cobble and gravel substrate will be removed. Native large cobble and small boulders will be placed on the riverward side of the remaining bar.
A buried grade control structure of 3-foot diameter, rounded or angular boulders or 2-foot diameter riprap will be built downstream of the excavated inlet to prevent channel headcutting (Design Sheets WW-1.0-1.1). This grade control structure will have 200 CY of boulders below OHW bedded with native alluvium and 3 to 4-inch cobble (Design Sheet WW-6.2).
- Pilot Channel - An excavator will dredge a 1,500-foot-long pilot channel beginning at the top of the island downstream to below the highway bridge (Design Sheets WW-0.2, 0.3, 1.0-3.2). Work will be done with a track excavator from the dewatered channel.
The bottom of the pilot channel will be 30-feet-wide; the top will be 42-feet-wide. The depth will be 1-2 feet as it grades into the existing channel. This pilot channel will direct flow to increase depth and velocity over the wave structure.
The pilot channel is designed to flush sediment through the east channel and minimize aggradation during normal flows. Some deposition will still occur, and routine excavation will be needed to maintain the inlet to the east channel, the inlet to the play area side channel, the channel depth above the wave, and the pool below the wave (see Routine Maintenance, below).
The pilot channel excavation downstream of the highway bridge will remove some of the depositional bar material as per the City’s requested requirement. The pilot channel will redirect flow away from the island to protect the east bank from erosion. Additional excavation of the pilot channel below the bridge will not be done as routine maintenance and is not covered by this consultation.
- Random Boulder Clusters - Large, partially buried boulder clusters will be used to provide play opportunities for boaters and kids (Design Sheet WW-6.2). Approximately thirty 6-foot-plus diameter, rounded boulders will be placed in the east channel above the wave (50 CY) (Table below). The play area will have ten 5 to 6-foot diameter, rounded boulders (32 CY). Ten more 3-foot diameter rounded or angular feature boulders will be installed as directed by the project engineer and project manager (32 CY). Native alluvium and 3 to 4-inch diameter cobbles will be used to key in the boulders.
- Bank Armoring at Island Park Below the Highway Bridge - A 180-foot long by 6-foot-high section of the island’s east bank will be armored with 4-tiers of 3-foot diameter, angular or square boulders (200 CY below OHWM) and 18-inch diameter riprap (115 CY below OHWM) as requested by the City to protect the bank from erosion. The rock terraced 2:1 slope profile is shown in Design Sheet WW-6.3
The proposed excavation and rock armoring will remove most of the woody vegetation, including most of the cottonwood trees. The project engineer and project manager will work with the contractor to avoid damaging or removing cottonwood trees whenever possible. The remaining trees are expected to provide a source for recolonization. New trees will not be planted since their survival in this location is unlikely.
The cottonwood trees that need to be removed will be used to create complexity in the play area or hauled to a location for storage until they can be used in other area river restoration projects. The SWPA will notify the Upper Salmon Basin Watershed Project about these trees and their availability.
SWPA volunteers will plant 200 coyote willow cuttings collected on-site within the rock terrace. The cuttings will be planted in clumps near the base of the armored bank, in the water table to increase their chance of survival.
Some clumps of coyote willow that are permanently removed to build the wave structure and access points to the wave and play areas will be planted above the armored bank to replace lost vegetation. The roots will be planted in the water table, a depth 6 feet or more, to increase the chance of survival.
De-watering - The east channel and side channel will be dewatered prior to construction (Design sheet WW-7.0). Sheet pile cofferdams installed with vibratory hammers will be used to dewater the channels. The cofferdam at the top of the island will direct flow to the main, west channel. The exact placement of the dams will be determined during low water levels. Example details of sheet pile cofferdam design are shown in design sheet: WW-7.1.
The excavator and materials for the water diversion will be stationed at the south end of the island and on the road below the highway bridge. The emergent wetland at the end of the island will be flagged to prevent equipment entry. The excavator will walk down the rocky bar at the south end of the island to avoid disturbance to the emergent wetland.
Dewatering of the east channel will be conducted slowly and in stages. In the first 24-hours the flow will be reduced by 1/3 to encourage fish to emigrate. Over the next 24-hours the remaining flow will be diverted to the west channel. The following protocol will be used to dewater the project area:
- Create settling basins and set up pumps with National Marine Fisheries Service (NMFS) criteria screens to pump excess groundwater and turbid water from the dewatered channel to settling basins. Example settling basin details are shown in Design Sheet WW-7.2.
- Settling basin outflow will be filtered through established vegetation where available and practical. When vegetation is not available, strawbales, wattles, or similar will be used to filter outflow water before it enters the river to ensure compliance with IDEQ water quality standards.
- The SWPA pump screens have been inspected by IDFG to ensure compliance with NMFS screen criteria.
- Install a cofferdam half-way across the top of the east channel for 24 hours.
- Install additional cofferdam across the top of the east channel to reduce flow to 1/4 of original flow for 10-12 hours.
- Install additional cofferdam across the top of the east channel so only 10% of original flow remains for 12 hours.
- Finish cofferdam to cut off all flow at the top of the east channel.
- Install cofferdam at the bottom of the east channel below the highway bridge.
The dewatered area will be 5.2 acres (2,550 feet long by variable width). Idaho Department of Fish and Game (IDFG) personnel will salvage fish during the dewatering process as the water recedes, following NMFS guidelines for electrofishing in waters occupied by ESA listed species (USDC NMFS 2000). IDFG will be notified and given a minimum 48-hour notice to be on-site for fish salvage prior to and during dewatering and cofferdam construction.
IDFG will complete a minimum of 2 upstream passes and 2 downstream passes with 2-4 electro-shocking units and at least 6-8 netters and bucket handlers. Work will cease if IDFG is not available to perform fish salvage operations.
Following dewatering and fish salvage, a track excavator will walk down the designated river access ramps into the dewatered channel.
The excavator will walk the length of the dewatered channel from the diversion dam at the top of the island to the end of the construction-site and the side channel play area from the inlet to the outlet to complete construction.
Sump pumps will be used as needed to maintain dry work environment when working below groundwater (e.g., wave and bottom row of the levee terracing). Submerged sump pump containment and discharge settling basin details are in Design Sheet WW-7.2.
ADDITIONAL INFORMATION: Two City of Salmon water pipelines run perpendicular to the east channel (Keller Associates design sheets). One pipeline is upstream of the highway bridge, the other is about 20 feet below the bridge (Design Sheets WW-2.0 and 5.0). New 24-inch diameter, high-density polyethylene (HDPE) casings will be buried 5-feet below the east channel’s bed elevation (to ensure they remain below the scour level) while the channel is dewatered. One casing will be 150-feet long, the other will be 175-feet long. The total casing fill below OHWM will be 38 CY.
The City will feed a new pipe through the casings in about 2 years when they do the waterline replacement project with no additional impacts (E. Penner, City Administrator and B. Green, Project Manager, pers. comm.). The old pipelines will not be removed. The City of Salmon has applied for a separate 404 permit for this part of the project (NWW-2021-304-I02), but it is being mentioned, as the City of Salmon will utilize the dry riverbed for their project.
Table - Fill types and volumes.
|
Structure
|
Material
|
Excavation
(CY)
|
Fill Below OHWM
(CY)
|
|
Excavation
|
existing alluvial material
|
2975
|
|
|
Grout/Concrete
|
3500 psi concrete mix
|
|
125
|
|
Wave Feature Boulders
|
6' plus in-channel, rounded
|
|
50
|
|
Play Area Feature Boulders
|
5'-6' boulders, rounded
|
|
32
|
|
Additional Feature Boulders
|
36" rounded or angular
|
|
32
|
|
Wave Structure
|
36" plus in-channel, rounded
|
|
700
|
|
Boulder Deflector
|
36" plus in-channel, rounded
|
|
150
|
|
Buried Grade Control
|
3' boulders - any kind OR 24"plus riprap
|
|
45
|
|
Levee Terracing
|
3' boulders, on bank, can be angular/square
|
|
1450
|
|
Play Area Terracing
|
2-3' boulders, rounded or angular
|
|
145
|
|
Island East Bank Armoring
|
3' boulders, on bank, can be angular/square
|
|
200
|
|
Type H Riprap
|
18" Riprap
|
|
115
|
|
Bedding Material
|
Clean 3-4” cobble and native alluvium
|
|
705
|
|
Surface Substrate Material (Play area)
|
Clean coarse sand ¼” minus
|
|
37
|
|
Two 2-foot Diameter Waterline Casings
|
High density polyethylene
|
|
38
|
|
Totals
|
|
2,975
|
3,824
|
CONSTRUCTION PERIOD: Applicant proposes to start construction on September 1, 2021 and end on December 20, 2021. However, the permit would authorize construction for a period of three (3) years.
PROPOSED MITIGATION:
The applicant has not proposed a compensatory mitigation plan. The application states that “we believe a mitigation plan is not needed as the project design criteria, best management practices (BMPs), and conservation measures described,” in the application and as shown on the attached drawings will prevent any long-term impacts to the site.
OTHER ENVIRONMENTAL DOCUMENTS AND DA PERMITS ISSUED TO APPLICANT: None
WATER QUALITY CERTIFICATION: The Idaho Department of Environmental Quality (IDEQ) is evaluating whether to certify that the discharge of dredge and/or fill material proposed for this project will not violate existing water quality standards. A Department of the Army permit will not be issued until water quality certification has been issued or waived by the IDEQ, as required by Section 401 of the Clean Water Act. Comments or questions concerning Water Quality Certification for this project should be mailed to: Idaho Department of Environmental Quality, Idaho Falls Regional Office, 900 N Skyline Drive, Suite B, Idaho Falls, Idaho 83402 or sent to Troy Saffle at troy.saffle@deq.idaho.gov.
AQUATIC RESOURCE DESCRIPTION: The Salmon River is confined by the flood control levee on the east bank of the east channel, topography, and development on the west bank of the west channel in the project area. This section of the river is prone to frazil ice that begins downstream below North Fork in the Deadwater reach and progresses upstream. The dominant substrate is embedded large gravel and cobble. There are no pools, limited undercut banks, low levels of large woody debris, and no spawning habitat.
The project actions will occur in the east channel and the adjacent side channel. The side channel holds groundwater and backwater but does not have a surface connection with the east channel during periods of low flow. Groundwater contributes a large volume of surface water to the east channel below the highway bridge where the channel turns sharply to the west and the east bank of Island Park. The project is bounded to the east by an existing flood control levee and to the west by Island Park. The extent of river work proposed would impact approximately 5.2 acres of channel (2520 feet). Given the level of development and usage indicated above this section of channel is heavily constrained physically (i.e. lateral movement is precluded and riparian vegetation is limited).
ANTICIPATED IMPACTS ON AQUATIC ENVIRONMENT:
A 5.2-acre area of east channel and side channel will be dewatered for 8-12 weeks (N. Werner, S2O engineer). The total dewatered channel length will be 2,550-feet; the width is variable.
About a ¼ acre of riparian vegetation will be temporarily impacted during construction. Another ¼ acre of riparian vegetation will be permanently removed for wave and play area access and terracing of the east bank of the island. Clumps of coyote willow that are removed from other project areas will be planted above the terrace rock. The rhizomes from these clumps will provide some limited recolonization within the rock.
The project would likely lead to short-term turbidity during dewatering, construction and rewatering. However, this is expected to be minimal given proposed BMPs. Mobile aquatic organisms such as fish would likely move from the area or be relocated as part of fish salvage. Non or less mobile aquatic organisms would likely be killed or crushed during dewatering and construction, however it is anticipated that they would quickly re-colonize the area once construction is complete. Longer term, the project would further fix the channel location as additional infrastructure would likely lead to increased efforts to maintain channel dimensions and flows.
OTHER AUTHORIZATIONS: Currently, we are coordinating with the Tribal Historic Preservation Offices for the Shoshone-Bannock Tribes to determine if there are any tribal historic or cultural interests within the project area.
The project area is in a floodway with outdated mapping. The Federal Emergency Management Agency (FEMA) required a Conditional Letter of Mapping Revision (CLOMR) as per the code of federal regulations 51 FR 30315: Floodway Revisions to update this information and address any potential project impacts. FEMA will give an approval based on the CLOMR. Then the County, as the local floodplain administrator, will issue a floodplain development permit based on the CLOMR. At the completion of the project, S2O Engineering will submit the as-builts and the related hydraulics to show the project was constructed as approved in the CLOMR. Then FEMA will issue a Letter of Mapping Revision (LOMR).
CULTURAL RESOURCES: The applicant has submitted a cultural resource survey for the proposed Salmon Whitewater Wavepark, dated January 2021, prepared by Sundance Consulting. Coordination is currently being conducted with the Idaho State Historic Preservation Office (ISHPO) to determine if this activity will affect a site that is listed on the National Register of Historic Places, or a site that may be eligible for listing on the Register. We are also coordinating with the appropriate Tribal entity or the Tribal Historic Preservation Offices for the Shoshone-Bannock Tribes, to determine if there are any tribal historic or cultural interests within the project area.
TRIBAL TREATY RIGHTS and INTERESTS: Federal agencies acknowledge the federal trust responsibility arising from treaties, statues, executive orders and the historical relations between the United States and American Indian Tribes. The federal government has a unique trust relationship with federally recognized American Indian Tribes, including the Shoshone-Bannock Tribes. The Corps has a responsibility and obligation to consider and consult on potential effects to Tribal rights, uses and interests. The Corps further recognizes there may be a need for additional and on-going consultation.
ENDANGERED SPECIES: The project is within the known or historic range of Columbia River bull trout, Snake River Basin steelhead, Snake River spring/summer Chinook salmon, and Snake River sockeye salmon. Coordination is currently being conducted with the U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service (NMFS/NOAA Fisheries) to determine if the activity will have any effect on species designated as endangered or threatened under the Endangered Species Act, or their critical habitat, under the Endangered Species Act of 1973 (87 Stat. 844).
ESSENTIAL FISH HABITAT: The Magnuson-Stevens Fishery Conservation and Management Act, as amended by the Sustainable Fisheries Act of 1996, requires all Federal agencies to consult with the National Marine Fisheries Service on all actions or proposed actions, permitted, funded or undertaken by the agency that may adversely affect Essential Fish Habitat (EFH). EFH species are known to use the project area. Preliminarily, we have determined the described activity would not adversely affect EFH.
ENVIRONMENTAL IMPACT STATEMENT: Preliminary review indicates the proposed activities will not require preparation of an Environmental Impact Statement. Comments provided will be considered in preparation of an Environmental Assessment.
EVALUATION: The decision whether to issue a Section 404 Clean Water Act permit will be based on an evaluation of the probable impact, including cumulative impacts, of the proposed activity on the public interest. This decision will reflect the national concern for both protection and utilization of important resources. The benefit which reasonably may be expected to accrue from the proposal must be balanced against its reasonably foreseeable detriments. All factors which may be relevant to the proposal will be considered, including the cumulative effects thereof; among those are conservation, economics, aesthetics, general environmental concerns, wetlands, historic properties, fish and wildlife values, flood hazards, floodplain values, land use, navigation, shoreline erosion and accretion, recreation, water supply and conservation, water quality, energy needs, safety, food and fiber production, mineral needs, consideration of property ownership and in general, the needs and welfare of the people. In addition, our evaluation will include application of the EPA Guidelines (40 CFR 230) as required by Section 404(b)(1) of the Clean Water Act.
408 EVALUATION: To ensure that Corps of Engineers, Civil Works project will continue to provide their intended benefits to the public, the proposed projects are evaluated by the appropriate engineering, real estate, and environmental team(s) to assess the alteration(s) and impacts that will occur during construction or occupation of the footprint. The 408 team will work in tandem with the Regulatory team to facilitate an expedient response to the applicant with an identified approval, adjustment/mitigation, or denial of the project under the 408 application.
CONSIDERATION OF PUBLIC COMMENTS: The Corps of Engineers is soliciting comments from the general public; Federal, State and local agencies and officials, Tribal entities and other interested parties in order to consider and evaluate the impacts of this proposed activity. Any comments received will be considered by the Corps of Engineers to determine whether to issue, modify, condition or deny a permit for this proposal and/or grant permission to alter a civil works project. To make this decision, comments are used to assess impacts on endangered species, historic properties, water quality, general environmental effects and the other public interest factors listed above. Comments are used in the preparation of an Environmental Assessment and/or an Environmental Impact Statement pursuant to the National Environmental Policy Act. Comments are also used to determine the need for a public hearing and to determine the overall public interest of the proposed activity.
PUBLIC HEARING: Any person may request in writing, within the comment period specified in this notice, that a public hearing be held to consider this proposed activity. Requests for a public hearing shall state specific reasons for holding a public hearing. A request may be denied if substantive reasons for holding a hearing are not provided or if there is otherwise no valid interest to be served.
COMMENT & REVIEW PERIOD: Interested parties are invited to provide comments on the proposed activity, which will become a part of the record and will be considered in the final decision.
Please mail all comments to:
U.S. Army Corps of Engineers
Walla Walla District
James Joyner
Idaho Falls Regulatory Office
900 N Skyline Drive, Suite A
Idaho Falls, Idaho 83402-1700
or
james.m.joyner@usace.army.mil
Comments should be received no later than the comment due date of July 24, 2021, as indicated on this notice, to receive consideration.