Water Quality Improvement Project
Lake Ketchum Area:
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
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While the farm is no longer active, the nutrient-rich soils contribute 23% of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.
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.
Snohomish County: Lake Ketchum Restoration
Lake Ketchum Algae Control Plan (Snohomish County publication)
WRIA 3: Lower Skagit-Samish
Watershed Information (Water web site)
Last updated March
WRIA: #3 (Lower Skagit-Samish)
# of TMDLs:
Under development as a straight to implementation project
Department of Ecology
3190 160th Ave. SE
Bellevue, WA 98008-5452