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Water Lily treatment along Lake Washington Beaches

This summer, Seattle Parks and Recreation (SPR) will continue the integrated weed management program to fragrant water lily infestations at selected lakefront properties on Lake Washington.

Controlling these weeds will improve water quality and recreational access at freshwater beaches, swim areas, moorages and other high- use recreation locations along the lake.

Mowing, hand cutting, and removal of the weeds will continue as in past years. SPR will complement this work by using selected aquatic herbicides. This use is permitted by Washington Department of Ecology (Ecology). These herbicides have been screened and endorsed by Ecology as an effective solution to control these noxious and invasive weeds. US EPA does not have a swimming restriction on the herbicide that will be used.  This is based on data provided to EPA for consideration.  The WA Dept of Ecology permit however does suggest a 24 hour swimming precaution and it should be posted out of an abundance of caution .

SPR has contracted with AquaTechnex, LLC to apply the selected herbicides. AquaTechnex, LLC will manage an online webpage with information and updates on the program.

To learn more about the permit and products:

To follow the project online:

The following beaches will be closed during the treatment:

Tuesday 7/17

Seward Park Beach

Stan Sayres

Wednesday 7/18

Madrona Beach

Mt. Baker Beach

Lakewood Moorage

Thursday 7/19

Magnuson Park Beach


For further questions, contact Project Coordinator Barb DeCaro,