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Allen Lake Outlet Project

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

Water over a roadway by Allen Lake.

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

  • Completed Feasibility Study January 2013
  • Completed Planning Phase February 2013

Beaver exclusion fence trash rack.

King County actions

  • We 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.
  • We replaced a failed driveway culvert, located approximately 1,450 feet downstream of Northeast 8th Street in March 2012.
  • We cleared 4 driveway culverts from Northeast 8th Street to approximately 1,800 feet downstream in December 2011.
  • We installed a beaver exclusion fence (317 KB) 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.
  • In 2015, we removed non-native vegetation and planted native plants along the channel from Northeast 8th Street to approximately 1500 feet downstream.

Deliverables

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

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

Notes from the Feb. 12, 2011 public meeting:

We prepared the Allen Lake Outlet Rapid Assessment:

We prepared the Allen Lake Outlet Feasibility Study:

We prepared the Allen Lake Outlet Stream Reconnaissance Report.

To report flooding, drainage, or water quality problems, visit our report a problem page or call us at 206-477-4811.

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