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King County worked on the Cottage Lake Phosphorus Reduction Project to control phosphorus pollution in the 63-acre lake Cottage Lake in north King County near Woodinville, Washington.  The project was largely funded by a grant by the Washington State Department of Ecology.

The project scope called for identifying, reducing, and controlling phosphorus pollution in Cottage Lake through education, restoration and implementing Best Management Practices by lake residents, while carrying out water quality monitoring to look for effects.

The project consisted of:

  • an extensive education and outreach program, including signage, workshops, a community newsletter and a survey of residents in the watershed both before and after the work was carried out;
  • A program of shoreline restoration that consisted of adding native plants, maintenance of the planted areas, and controlling noxious weeds,;
  • A program of water quality monitoring for the lake and associated stream inlets including total nitrogen, nitrate, fecal coliform bacteria, dissolved oxygen, orthophosphate, temperature, pH, turbidity, total suspended solids, color, alkalinity, conductivity, chlorophyll a, phytoplankton and water transparency.
  • A lake shore and in-stream habitat assessment was conducted; 
  • Restoration projects were identified for both private and public lands and implemented as far as possible and,
  • Water quality data was entered into the state’s EIM database to share information with interested parties.

Project documents are provided in Adobe Acrobat for viewing.  For help using Acrobat, please see our Acrobat help page.

Download project report here:

Project grant

The Cottage Lake Phosphorus Reduction Project was funded by the Washington State Department of Ecology using Centennial Clean Water Funds.

The project began in June 2005 and the project performance period was through June 2011. Total funding was estimated at:

    $218,796 State Department of Ecology (EPA)
    $  72,932 King County
    $291,728 TOTAL project fund

For questions about lakes in King County, please contact or call the Water and Land Resources Division front desk at 206-477-4800.