June 23, 2024
Washington State's Department of Ecology has completed its EIS process and chosen a replacement dam that would raise Eightmile Lake, according to Ecology's figures, by four feet.
The concrete dam, according to Ecology, would have a 180 foot wide spillway and flood an additional 4.8 acres. During maximum drawdown an additional 2.5 acres of lakebed would be exposed. The dam would have no gates. Water would be withdrawn through a submerged outlet pipe, controlled by an automated plug valve that would allow the irrigation district to remotely adjust the amount of water released.
Engineering design comes next, but Ecology acknowledges that several permits will be needed before construction can start. The most critical is probably one from the U.S. Forest Service. The irrigation district has grandfathered rights to a dam at Eightmile Lake, but at least one major question will be whether that existing private right includes the right to expand the lake's size and drawdown within the Alpine Lakes Wilderness. This question involves the Wilderness Act, which was not the focus of Ecology's EIS process.
Access to the Final EIS and a separate Appendix of Ecology's response to comments on its draft EIS is available at https://apps.ecology.wa.gov/publications/SummaryPages/2412004.html