The Impacts of Alum Treatment on Waughop Lake, Pierce County
BY COLIN GLAZE
Some 12 thousand years ago, receding glaciers gouged and carved the Puget Sound landscape as Earth left its latest ice age. Ice blocks left behind during the retreat eventually melted and left depressions in the ground, called kettle lakes for their resemblance to filled pots of water. Waughop Lake, a small body of water located in Fort Steilacoom Park, Lakewood, is one of many of these in kettles in Washington, but it has a very scummy problem. Waughop is a very peaceful lake, where many people come to walk with friends or to set up fishing stations on the beach to try for trout. Unfortunately, the lake has been struggling with hazardous algal blooms (HABs) for many years, and is therefore unsafe for swimming or drinking (a real worry for pet owners). HABs are caused by elevated levels of nutrients in the lake. The lake has no substantial inflows or outflows other than storm water runoff and percolation of groundwater around the lake. Therefore, problems like elevated nutrients that arise stay in the lake for much longer than other lakes with outflows.While they can form naturally, HABs are often initiated or exaggerated by anthropogenic sources, which is the case at Waughop.
BELOW: “Waughop Lake” by B.D.’s World, licensed under CC BY-SA 2.0 (1)
ABOVE: Example of an algal bloom. The history of Waughop Lake has been bumpy and, until recently, it was treated less like a lake and more like a waste lagoon. From 1870 until 1965 there was a hog farm located near the lake, and many of the buildings still remain. During this period of time, all animal and human waste from the farm was dumped directly into the lake, and there was even a slaughterhouse over one corner of the lake with a grated floor to allow blood and other animal products to fall easily into the water. While this practice has since been discontinued, the negative impact of humans on the lake has not stopped there. In more recent years, it was discovered that a sewage pipe from the nearby Pierce College had broken and the waste from the campus was running directly into the lake. Together, these events have thrown the nutrient levels in the lake out of balance and have fueled the HABs, which seem to get larger and larger each year. In the summer of 2020, the City of Lakewood hired a company to apply a treatment of aluminum sulfate (alum) to the lake in the hopes of stopping the algal blooms. Alum works by binding the aluminum to free phosphorus in the lake. With the phosphorus bound to the aluminum, it is no longer free to fuel the algal blooms and thus the alum cuts off the HAB cycle. In order to do this effectively, 21,477 gallons of aluminum sulfate were
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