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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 multiple times since the early 1990’s.

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 stabilize an existing 12” diameter, 350 foot long section of pipeline. A temporary pump will be installed during pumping operations. This project will connect to a pipeline that runs approximately 1 mile to the south and discharges at an infiltration facility. See the attached documents for details on the proposed project.

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 2019
Completion of Environmental Review and Permitting Mid 2020
Construction 2021

Project Documents

SEPA Documents

Environmental Information related to proposal (Documents e and l will not be publicly distributed):

Project Manager

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

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