Lake Ketchum is a 26-acre public lake located in northwest Snohomish County two miles north of the City of Stanwood. The lake supports swimming, fishing, boating, aesthetic enjoyment, and wildlife habitat. 

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For many years, Lake Ketchum suffered from thick growths of blue-green algae. These algae blooms formed unsightly scums on the lake surface that severely impaired use and enjoyment of the lake. The algae blooms, caused by too much phosphorus in the lake, were also frequently toxic, threatening the health of people and pets that used the lake.

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Through an ongoing collaboration between Snohomish County and the Lake Ketchum community, the lake water quality has been successfully restored. Specifically, phosphorus levels have dramatically decreased, algae growth has been substantially reduced, and the water is significantly clearer. The Lake is once again healthy allowing people to swim, play, and boat in the lake and are evident for all to see. However, additional action is needed each year to ensure that Lake Ketchum remains healthy.

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The most critical item of the restoration plan was an initial large-scale alum treatment followed by smaller annual maintenance alum treatments. Alum treatments are the most successful method used around the world for controlling phosphorus in lakes because: 

• Alum permanently binds phosphorus in the water and sediments so that it is no longer available to grow algae.

• Alum is a non-toxic material commonly used in drinking water treatment plants to clarify water.

• Alum has no lasting negative impacts to the lake or aquatic wildlife.

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Link to Lake Ketchum History Document

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Lake Ketchum Snohomish County Site