CENWP-PM-E-14-10

                                                                                                       Issue Date: August 15, 2014                                           Expiration Date: Sept 29, 2014

The U.S. Army Corps of Engineers, Portland District (Corps) is seeking public comment on the Mount St. Helens Sediment Management Plan Supplemental Environmental Impact Statement.  The Corps is evaluating several alternatives in the draft SEIS, outlining strategies to manage flood risk to established levels for the cities of Castle Rock, Lexington, Kelso and Longview, Washington through the year 2035.   The draft SEIS is available on the Corps webpage at: http://www.nwp.usace.army.mil/Missions/Currentprojects/MountStHelensEIS.aspx

The public comment period begins Aug. 22, 2014 and continues for 45 calendar days. Comments must be received via email, or via traditional mail, must be postmarked by Oct. 6, 2014.

The original Mount St. Helens Sediment Management plan, authorized in 1985, included construction of a sediment retention structure, levee improvements and dredging.  In addition, the original plan indicated that additional sediment management actions would be needed sometime after year 2000 and acknowledged other actions besides dredging might be more appropriate in the future. Current efforts focus on identifying remaining actions needed to complete the original MSH project and the associated impacts. 

Current data indicates additional sediment management actions are needed to prevent increased flood risks associated with sediment deposition in the lower 20 miles of the Cowlitz River.  Recent assessments show that unless further actions are implemented, sediment buildup in the lower Cowlitz River will continue and increase the flood risk for more than 50,000 people, their homes and businesses.  Flood risk levels for the communities of Lexington, Kelso, Castle Rock and Longview would continue to deteriorate as the river channel fills with sediment.  Without sediment management actions, the floodwaters could eventually overtop the levees and significantly impact the communities. 

Three alternatives were identified that would address the flood risks associated with sediment build up in the lower Cowlitz River through 2035.  They are:

1.       Cowlitz River dredging only

2.      SRS spillway and embankment raise

3.      A phased construction plan consisting of:

a.       SRS spillway crest raises

b.      Grade-building structures

c.       As needed dredging

Environmental impacts for the three alternatives have been evaluated and are reported in the draft SEIS.  The SEIS was prepared by the Portland District.  Formal consultation with the U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Administration (NMFS) is also being conducted for the preferred plan. 

The Corps has selected the phased construction alternative as its preferred alternative.  Based on research and analysis, the Corps determined that this alternative provides specific actions and necessary flexibility to manage the flood risk to cities near the Cowlitz River. For more information about the preferred alternative and all other alternatives, please see the draft SEIS document on the Corps’ website.