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Water and Land Resources Division

King County, Washington

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Water and Land Resources Division, King County, Washington

Lake Allen outlet project

Allen Lake outlet roadway flooding
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 across Northeast 8th Street, near 250th Avenue Northeast, restricting access to homes. In response, King County initiated an effort to document the flooding, and to begin planning for the most effective way to reduce the flooding.

In 2015, King County Water and Land Resources Division (WLRD) will remove non-native vegetation and plant native plants along the channel from Northeast 8th Street to approximately 1500 feet downstream. The division is looking for grant funding opportunities to replace six culverts along the channel with new, larger culverts that will improve flows along the channel.

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. 
N.E. 8th St. Beaver Exclusion Fence and replaced trash rack near 250th Ave. N.E.
  • Completed Feasibility Study January 2013;
  • Completed Planning Phase February 2013

King County actions

  • 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 2012;
  • King County cleared 4 driveway culverts from Northeast 8th Street to approximately 1,800 feet downstream in December 2011;
  • 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;
  • 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 and June 2014.

Deliverables

King County hosted a public meeting on October 29, 2014 and materials from the meeting are available:

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

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

King County has prepared the Allen Lake Outlet Rapid Assesment.

King County has prepared the Allen Lake Outlet Feasibility Study.

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

Allen Lake Outlet Project location map
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.