March 19, 2025
In 2014 the City of Lakewood received a grant from the state Department of Ecology to develop a lake management plan for Waughop Lake.
Located in Fort Steilacoom Park, the shallow body of water sees many visitors who walk, run or bike the 1-mile paved trail around its perimeter. Visitors watch birds, fish and race model boats on the lake.
Waughop Lake has a long history of toxic cyanobacteria blooms, also referred to as harmful algae blooms. It has deteriorated water quality due to decades of poor waste management practices. Manure and other agricultural waste were dumped into the lake between 1900 and 1965 from a farm operated by Western State Hospital.
These discharges led to the buildup of loose, nutrient rich sediments. These sediments have fueled nuisance algae growth and toxic cyanobacteria blooms. Between 2008 and 2018, it was common for the Tacoma-Pierce County Health Department to issue health advisories restricting contact with the water.
Waughop Lake is 33 acres (approximately 0.25 miles in diameter at its longest point). It is only 7 feet deep with water levels at their highest point. Rainwater, ground water and storm runoff are its primary water sources. The lake does not feed into creeks or streams. Instead, the water is retained on site. The water levels rise and fall with ground water.
During the summer, overall water depth reduces to 3 to 4 feet at the deepest point. This shallow depth during the hotter months, coupled with the nutrient rich sediments, caused the toxic blooms in this small body of water.
The city developed a lake management plan with the water body’s many constraints in mind. This included the shallow depth, the nutrient rich sediment and the lack of new water regularly cycling through to flush the lake.
The plan identified treating the lake with aluminum sulfate (alum) to remove phosphorus from the water column and inactivate phosphorus in the sediments. This practice is common and does not result in long-term impacts to pH or alkalinity in water.
Using alum as a treatment is a longstanding practice in lake management nationwide. It has been used to treat water bodies for 50 years. It is used in 250 lakes across the country, including other well-known lakes in Washington. They include Seattle’s Green Lake, Lake Fenwick in King County, Black Lake in Thurston County, Stanwood’s Lake Ketchum and Lake Stevens in Snohomish County.
The city looked at dredging the lake to remove the phosphorus-rich bottom sediments. This option was not finically feasible and would negatively impact Fort Steilacoom Park. It would require a 20-acre treatment pond, and the city would have to close off 30 acres of the park to dry the sediments for at least a year.
In 2020 and again in 2023 Waughop Lake was treated with drinking water treatment-grade alum to reduce phosphorus concentrations and mitigate toxic algal blooms. The city received a permit from the state Department of Ecology to conduct the treatment. The permit required monitoring and testing of the lake.
The treatments dramatically reduced phosphorus availability in Waughop Lake. They prevented toxic algae blooms in 2020, 2021, 2023 and 2024, even with elevated chlorophyll concentrations (the amount of algae in the lake) in late 2023 and throughout 2024.
Because of the alum treatments, Waughop Lake has not experienced a toxic algae bloom for the first time in over a decade. Detections of cyanotoxins are below state recreation guidelines.
The alum treatments have been effective in reducing phosphorus concentrations and subsequent cyanobacteria blooms, providing a safer lake environment for the community.