Water Quality Improvement Project
Lake Ketchum Area:
Total Phosphorus


Lake Ketchum is a 26-acre lake located in unincorporated Snohomish County, near the city of Stanwood. Historically, Lake Ketchum served as the drinking water supply for Stanwood. However, in recent decades the lake has experienced ever-increasing toxic algal blooms and excessive aquatic plants growing throughout the lake. (See Study Area map)

Water quality issues

Toxic algae blooms in Lake Ketchum are primarily due to uncontrolled sources of pollution entering the lake from a nearby farm and from buildup of phosphorus in lake sediments. Lake Ketchum has been noted as the most polluted lake in Snohomish County since 1997 and is on Ecology’s 303(d) list of polluted waterbodies for phosphorus.

Excessive amounts of phosphorus has led to chronic blue-green (cyanobacteria) algae blooms. Results of Lake Ketchum’s testing of algae show toxicity has been as high as 551 ug/L. The recreational guideline for toxicity in water is 6 ug/L. While the farm is no longer active, the nutrient-rich soils contribute 23% of the annual phosphorus pollution, and the farm’s phosphorus-rich sediments account for 73% of the annual pollution in Lake Ketchum.

Lake Ketchum, Washington State.  Photo courtesy of Tricia Shoblom, WA Department of Ecology.

Status of the project

Ecology is developing a straight to implementation (STI) project to determine the source(s) of phosphorus pollution and develop a strategy to bring Lake Ketchum back in to water quality standards.


Why this matters

A high level of blue-green algal blooms has led to a decline of beneficial uses like swimming, fishing and aesthetic enjoyment.  Snohomish Surface Water Management (SWM) has determined Lake Ketchum to be their highest priority lake.


Technical information

Snohomish County: Lake Ketchum Restoration


Related information

Lake Ketchum Algae Control Plan (Snohomish County publication)

WRIA 3: Lower Skagit-Samish Watershed Information (Water web site)


Last updated March 2016
  Water Resource Inventory Area (WRIA) 3 map, Washington State.


WRIA: #3 (Lower Skagit-Samish)
County: Snohomish

Water-body Name:
Lake Ketchum

Total Phosphorus

# of TMDLs:

Under development as a straight to implementation project

Contact Info:
Tricia Shoblom
Phone: 425-649-7288
Email: Tricia.Shoblom@ecy.wa.gov

Northwest Region
Department of Ecology
3190 160th Ave. SE
Bellevue, WA 98008-5452