The Allen Lake Outlet Feasibility Study evaluated solutions to chronic flooding at the outlet of Allen Lake on the Sammamish Plateau. The goal is to maintain safe access to households that use Northeast 8th Street.

The objectives of the Allen Lake Outlet Feasibility Study were to:

• Evaluate the feasibility of alternative solutions intended to improve road access;
• Perform hydrologic and hydraulic modeling analysis for each alternative; and
• Determine a recommended alternative.

Four alternatives were evaluated during the course of this study:

1. construction of an emergency access road;
2. construction of Northeast 8th Street to a higher elevation;
3. construction of an outlet channel to the west, and
4. improvement of the flow capacity of the existing channel.

The recommended alternative is improvement of the flow capacity of the existing channel. This would be done by replacing three culverts north of Northeast 8th Street and planting native plants along the channel.

The Allen Lake Outlet Feasibility Study is provided in Adobe Acrobat format for compatibility with a wide variety of browsers and computer systems. For help with Acrobat, please see our Adobe Acrobat help page.

Download here:

• Allen Lake Outlet Feasibility Study  (5.6 Mb)

For questions about the Allen Lake Outlet Feasibility Study, please contact Claire Jonson, Senior Engineer, King County Surface Water Engineering Services.

Related information

• Lake Allen Outlet Project
• Allen Lake
• Stormwater services and information

Related agencies

• Dept. of Natural Resources and Parks
• Water and Land Resources Division