The U.S. Army Corps of Engineers has extended the public comment period to Oct. 21 for a draft Supplemental Environmental Impact Statement and Mount St. Helens Long Term Sediment Management Plan. The comment period was scheduled to end Oct. 6
The Corps is evaluating several alternatives in the draft SEIS to manage flood risk for the cities of Castle Rock, Lexington, Kelso and Longview, Washington through the year 2035.
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.
The draft SEIS identifies remaining actions needed to be completed from the original MSH project and focuses on the actions’ associated impacts.
In addition to a No Action alternative, 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, with formal consultation with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service.
The Corps 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.