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Horseshoe Lake is a closed depression located in unincorporated King County just west of the City of Black Diamond. There are fifteen single family residences along the waterfront. Horseshoe Lake does not have a surface water outlet however it is hydraulically connected to groundwater and is subject to rapid changes in elevation. The rising water level of Horseshoe Lake threatens both homes and infrastructure. Emergency pumping of Horseshoe Lake is required to maintain roadway access, protect property and protect the environment by preventing flooding of septic systems. King County has performed emergency pumping seven times (1991, 1996, 1997, 2007, 2009, 2011, and 2014).

May Creek sediment removal location plus wetland enhancement on west side of 148th

Horseshoe Lake Project Location

Project Overview

Re-establishing equipment access and clearing of an area to place a pump each time that there is a threat of flooding is costly, time consuming and creates the potential for an unintended expansion of impacts adjacent to the edge of Horseshoe Lake. King County DNRP is designing a project to permanently establish an access driveway from SE Auburn-Black Diamond Road to Horseshoe Lake and to install a buried 12” diameter, 140 foot long permanent pipeline alongside the driveway. A temporary pump and suction line from Horseshoe Lake will be installed during pumping operations. The 140 foot long pipe will either continue to a proposed regional storm water facility, approximately 1 mile to the south or the pipe will continue to other alternate, yet to be determined locations.

Project Goals

  • Reduce threat of flooding to Horseshoe Lake residences and infrastructure.
  • Establish Permanent Access road and location for future pumping operations.

Project Timeline

Milestone Date
Completion of SEPA Process Late 2015
Completion of Environmental Review and Permitting Early 2016
Construction Early 2016

Project Documents

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Project Manager

For questions about this project, please contact Wes Kameda, project manager, WLR, Capital Services Unit