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Intent To Prepare a Draft Environmental Impact Statement, Programmatic Sediment Management Plan, Lower Snake River Reservoirs, in the States of Washington and Idaho

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Department of the Army, U.S. Army Corps of Engineers, DoD.


Notice of intent.


The U.S. Army Corps of Engineers (Corps) intends to prepare an Environmental Impact Statement (EIS) for a Programmatic Sediment Management Plan that will address sediment management within the four lower Snake River reservoirs and that portion of McNary reservoir contained within the lower Snake River The plan will identify and evaluate ways the Corps can manage sediment within these reservoirs and examine the sediment input (sources) on a programmatic basis in the near-term, mid-term, and long-term. The reservoirs extend from the mouth of the Snake River upstream to the communities of Lewiston, Idaho, and Clarkston, Washington; and include the lower 2 miles of the Clearwater River from its confluence with the Snake River at Lewiston upstream to the U.S. Highway 12 Bridge. In the plan the Corps will also include all tributaries that could significantly contribute sediment to the lower Snake River. The Corps is preparing this plan because sediment management has been an ongoing maintenance issue since the completion of Ice Harbor Dam, the first dam and reservoir on the lower Snake River, in 1961. Rather than addressing sediment-related problems on a case-by-case basis, the Corps has determined that it would be more effective to evaluate sediment management as a whole and on a watershed basis. The intent of the plan is to identify ways to reduce the amount of sediment entering the reservoirs, identify how to manage the sediment once it enters the reservoirs, and identify possible changes to structures or operations to reduce maintenance and associated impacts while still providing for authorized project purposes, including navigation.

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Mr. Carl Christianson, Project Manager, Walla Walla District, Corps of Engineers, CENWW-PM-PD, 201 North Third Avenue, Walla Walla, WA 99362, phone (509) 527-7260, or Ms. Sandra Simmons, NEPA Coordinator, Walla Walla District, Corps of Engineers, CENWW-PD-EC, 201 North Third Avenue, Walla Walla, WA 99362, phone (509) 527-7265.

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Since construction of its first dam on the lower Snake River, the Corps has recognized that sediment management would be an ongoing maintenance issue within the reservoirs. Historically the Corps has used dredging as the primary means of managing sediment that deposited in areas that interfere with man's use of the river. Most of these maintenance dredging actions have been conducted on a case-by-case basis without a long-term look at more effective ways of managing sediment. The Corps has now determined it would be more effective to evaluate sediment management within the lower Snake River on a watershed scale, and evaluate the potential for reducing sediment input, rather than focusing only on the reservoirs themselves. Although the Corps does not have the authority to manage land outside of the reservoir project boundaries, the Corps can identify and evaluate management strategies that could be implemented on non-Corps property.

The Corps is considering a variety of sediment management measures that could be used individually or in combination. Measures identified to date for evaluation include:

Sediment Reduction Measures

Structural Sediment Reduction Measures

  • Aquatic ecosystem restoration projects under current authorities (Section 206 Water Resources Development Act of 1996 and Section 1135 of the Water Resources Development Act of 1986)
  • Shoreline vegetated filter strips
  • Streambank erosion control
  • Improved logging road placement and design

Non-Structural Sediment Reduction Measures

  • Natural Resource Conservation Service conservation programs
  • Land use planning
  • Public education
  • Watershed planning
  • Forest management practices
  • Timber harvest planning

Sediment Management Measures

In-water systems to control sediment deposition.

  • Agitation to prevent settling
  • Bendway weirs
  • Dikes and dike fields
  • Air curtains to prevent settling of material at specific locations

Sediment Removal and Management

  • Agitation to re-suspend sediment
  • Dredging to remove sediment
  • Beneficial use of dredged material
  • In-water disposal of dredged material
  • Upland disposal of dredged material

System Management Measures

Modify Navigation System Infrastructure

  • Relocate affected commercial navigation, recreational boating and water intake facilities
  • Build sediment retention dams upstream of Lower Granite reservoir and/or in tributaries

Modify Reservoir Operations

  • Raise pool levels to increase water depth
  • Modify flows to flush sediment
  • Draw down Lower Granite reservoir to add flow conveyance capacity

Provide Flow Conveyance at Snake/Clearwater Rivers Confluence

The Corps has also initially identified several key resource areas that may be affected by the sediment management Start Printed Page 57570measures and will be analyzed in the EIS. These include water quality, anadromous fish, cultural resources, and socio-economics. The Corps expects other resource concerns to be identified during the scoping process.

The EIS will address measures, alternatives, and impacts on a programmatic level, but will not address site-specific actions. However, the EIS will present the coordination and environmental review steps the Corps will take with regard to subsequent site-specific actions.

The Corps currently anticipates conducting public scoping for this EIS in early 2006. The exact dates, times, and locations of these meetings have not yet been set. The Corps will publicize this information once the meeting arrangements have been made. The Corps invites affected Federal, state, and local agencies, affected Native American tribes, and other interested organizations and persons to participate in the development of the EIS. The Corps will also invite input from the local, interagency sediment management group formed under the Northwest Regional Dredging Team.

The draft EIS is currently scheduled to be available for public review in fall 2008. The final EIS is currently scheduled to be available for public review in fall 2009.

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Randy L. Glaeser,

LTC, EN, Commanding.

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[FR Doc. 05-19694 Filed 9-30-05; 8:45 am]