Lake Allen Outlet Project

Flooding over roadway at Northeast 8th Street near 250th Avenue Northeast during the December 2010 storm event

Project description
In 2010, residents around Lake Allen in the Sammamish area reported that the lake outlet flooded Northeast 8th Street, near 250th Avenue Northeast, restricting access to homes. In response, King County initiated an effort to document the flooding, and begin planning for the most effective way to reduce the flooding.

King County Water and Land Resources Division (WLRD) is proceeding with a feasibility study that incorporates hydrologic/hydraulic modeling of the Lake Allen outlet channel to evaluate the effectiveness of alternative capital projects to solve the problem.

Project goals
To reduce flooding over roadway in the vicinity of Northeast 8th Street from 245th Place Northeast to 250th Avenue Northeast by developing alternative solutions and implementing cost effective measures.

Summary milestone schedules

 
N.E. 8th St. Beaver Exclusion Fence and replaced trash rack near 250th Ave. N.E.

• Complete Draft Feasibility Study by: September 17, 2012
• Complete Planning Phase by: December 31, 2012
• Complete Pre-design Phase by: June 30, 2013
• Complete Final Design Phase by: December 31, 2013
• Complete Implementation Phase by: December 31, 2014
• Complete Closeout Phase by: December 31, 2015

Current events

• October 27, 2012 public meeting to update Lake Allen community residents on the Sammamish Plateau about plans to reduce persistent flooding in the area.  The meeting will take place from 10:30 a.m. to noon at Good Samaritan Episcopal Church 1757 244^th Ave. N.E., Sammamish.
• King County hand removed non-native vegetation and obstructions in the Allen Lake Outlet Channel from NE 8th Street to approximately 1,050 feet downstream in August 2012.
• King County replaced a failed driveway culvert, located approximately 1,450 feet downstream of Northeast 8th Street in March.
• King County cleared 4 driveway culverts from Northeast 8th Street  to approximately 1,800 feet downstream.
• WLRD has installed a beaver exclusion fence (Acrobat pdf) at the inlet of pipe system at Northeast 8th Street near 250th Avenue Northeast during June 2011.
• WLRD may provide maintenance assistance to private home owners to clear invasive vegetation and visible obstructions to the Lake Allen downstream channel.
• King County Department of Transportation has replaced the damaged trash rack on Northeast 8th Street in July 2011.
• King County Department of Transportation cleaned out the pipe system on Northeast 8th Street in June 2011.

Deliverables

King County hosted a public meeting on October 29, 2011 and notes from the meeting are available:

• Oct. 29, 2011 public meeting notes (Acrobat pdf)
• Oct. 29, 2011 public comments (Acrobat pdf)

Notes from King County's Feb. 12, 2011 public meeting:

• Feb. 12, 2011 Public meeting notes (Acrobat pdf)
• Feb. 12, 2011 Public meeting facilitator's comments (Acrobat pdf)

King County has prepared the Allen Lake Outlet Rapid Assesment.

• View the Allen Lake Outlet Rapid Assessment

King County has prepared the Allen Lake Outlet Feasibility Study.

• View the Feasibility Study

King County has prepared the Allen Lake Outlet Stream Reconnaissance Report.

• View the Stream Reconnaissance Report

Allen Lake Outlet Project vicinity map

To report drainage complaints, please visit our drainage and water quality report investigation page.

For more information about Lake Allen Outlet Project, please contact Claire Jonson, Project Manager, WLR Capital Services Unit. or Jon Cassidy, Maintenance Engineering Manager, KCDOT Engineering and Inspection Services.