US Army Corps of Engineers
Walla Walla District Website

Programmatic Sediment Management Plan

Note as of Nov. 18, 2014, 11:02 a.m.: The "PSMP RODs package" was updated with minor corrections. The link name on the right-hand side of this page is now "PSMP RODs Package Corrected4" to indicate that this version 4 replaced the previous "version 3" loaded last night.

Corps finalizes Lower Snake River Programmatic Sediment Management Plan

Following intensive U.S. Army Corps of Engineers review and consideration of extensive public comments, the Corps’ Northwestern Division Commander, Brig. Gen. John S. Kem, signed two Records of Decision (RODs) on Nov. 14, 2014, for 1) the Lower Snake River Final Programmatic Sediment Management Plan (PSMP) and 2) a current “immediate need” action (dredging) to reestablish the congressionally authorized dimensions of the Lower Snake River federal navigation channel. The RODs are based on consideration of reasonable alternatives and evaluation of potential environmental effects contained in the PSMP Final Environmental Impact Statement (PSMP FEIS). Signing of the RODs marks completion of the Walla Walla District National Environmental Policy Act (NEPA) review process.

 The first ROD signed by Brig. Gen. Kem was for the long-term, comprehensive Programmatic Sediment Management Plan for managing sediment accumulation that interferes with existing authorized purposes of the Corps’ four lower Snake River dam and reservoir projects (Ice Harbor, Lower Monumental, Little Goose, and Lower Granite) in southeastern Washington and north central Idaho. The affected authorized project purposes are navigation, recreation, fish and wildlife conservation, and flow conveyance. The Corps evaluated potential environmental effects of a range of sediment management alternatives, consulted with the public and other agencies, and developed a “toolbox” of measures for addressing future problem sediment.

 The second signed ROD was for a current “immediate need” action (dredging) to re-establish two areas of the federal navigation channel—1) the navigation lock approach at Ice Harbor Dam and 2) at the confluence of the Snake and Clearwater rivers--to congressionally authorized dimensions of 14 feet deep by 250 feet wide at minimum operating pool (MOP). Maintenance dredging last occurred in the lower Snake River navigation channel in the winter of 2005-2006.

 Dredging is the only effective short-term tool available for maintaining the federal navigation channel to congressionally authorized dimensions. The Corps plans to dredge during the first available winter “in-water work window,” Dec. 15 to Feb. 28, when salmonid fish are less likely to be present in the river. The Corps plans to use the dredged material to create shallow-water habitat for juvenile salmon at Snake River mile 116, just upstream of Knoxway Canyon and 23 miles downstream of Clarkston. 

 The Corps plans to perform federal navigation channel maintenance dredging activities at two locations: 1) the downstream navigation lock approach at Ice Harbor Dam, and 2) the confluence of the Snake and Clearwater rivers in Lower Granite reservoir. The Corps plans to use the dredged material to create shallow-water habitat for juvenile salmon at Snake River mile 116, just upstream of Knoxway Canyon and 23 miles downstream of Clarkston.

 Ports of Lewiston and Clarkston Berthing Areas Maintenance (Dredging)

In addition, the Corps issued on Nov. 14, 2014, Clean Water Act Section 404 and Rivers and Harbors Act Section 10 permits to the Port of Lewiston, Idaho, and the Port of Clarkston, Wash., for ancillary/related berthing area maintenance dredging. Those berthing areas are adjacent to the federal navigation channel. The PSMP Final EIS considered potential environmental effects for the berthing area maintenance dredging, which is planned to occur in conjunction with the Corps federal navigation channel maintenance. The Ports are funding the berthing area maintenance dredging and all associated administrative and environmental review costs. 

 The Corps’ Walla Walla District is responsible for the Regulatory permit action in the state of Idaho including the Port of Lewiston. The Corps’ Seattle District is responsible for the Regulatory permit action in the state of Washington including the Port of Clarkston.

 Public Involvement is Part of the Corps Review Process

The U.S. Army Corps of Engineers, Walla Walla District (Corps), invited public review and comment on the Lower Snake River Final Programmatic Sediment Management Plan and Environmental Impact Statement (PSMP FEIS) from Aug. 22, 2014, through Sept. 22, 2014.

 Previously, a public meeting was held in Lewiston, Idaho, on Jan. 24, 2013, and public comments on a draft EIS were accepted Dec. 21, 2012 through March 26, 2013.

 A separate public comment period regarding Clean Water Act (CWA) compliance for a proposed dredging and in-water disposal action was held March 11, 2013, through April 30, 2013.

 In addition, public comments were invited from Nov. 19, 2013, to Dec. 18, 2013 on Port of Lewiston and Port of Clarkston applications for Corps Regulatory permits to maintain (dredge) port berthing areas and dispose of dredged material.

 PSMP Final EIS documents and related documents are available in electronic form via the links on the right side of this page. Note Draft EIS Appendix H is now incorporated with Final EIS Appendix L (CWA Section 404(b)(1) Evaluation).

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The study area extends from the mouth of the Snake River upstream to the communities of Lewiston, Idaho, and Clarkston, Washington. It also includes the lower 2 miles of the Clearwater River, from its confluence with the Snake River in Lewiston upstream to the U.S. Highway 12 Bridge. All tributaries that significantly contribute sediment to the lower Snake River have been included in the study. See link to the study area map in upper right-hand corner.

Although the Corps does not have the authority to manage lands outside of the reservoir project boundaries, management strategies for non-Corps property have been identified and evaluated.

While site-specific locations are not addressed in the EIS, the coordination and environmental review steps required to accomplish subsequent site-specific actions are presented.


The Local Sediment Management Group (LSMG), originally formed in 2000, provides agency and stakeholder input to the U.S. Army Corps of Engineers, Walla Walla District, on sediment management within the lower Snake River drainage area.

The LSMG plays an important role in the implementation of Corps sediment management activities, and is a forum to address regional sediment issues. LSMG members include tribes plus state and federal agency representatives. Public ports within the study area also participate, as do other entities with an interest in sediment management such as  land management agencies, environmental groups, and transportation interests.


While the LSMG originally focused primarily on dredged material management, its purpose has been expanded. The LSMG now assists with the identification of sediment sources in all tributary watersheds to the lower Snake River reservoirs and with informing the group of recent studies, projects, and techniques related to sediment management in the region. This group's formation and direction is consistent with the guidance on formation of local planning groups provided by the National Dredging Team (NDT). The LSMG will continue to develop in accordance with policies and procedures for the EPA’s Regional Dredging Team (RDT) , as referred in the April 26, 2002, policy letter jointly signed by Brigadier General David A. Fastabend (Corps of Engineers, Northwestern Division Commander) and L. John Iani (EPA, Region 10, Administrator).  The LSMG charter defines the roles and responsibilities of the LSMG members and set up the group structure.