By Tom McClellan, Part 1 of 2
There is a big risk that the Lakewood City Council is going to make a bad decision on March 6, one that will end up harming the environment. The City’s consulting firm, Brown and Caldwell, has finally wrapped up a study first commissioned in 2014, and is recommending a chemical treatment of Waughop Lake to help with the persistent toxic algae problems. This is a really bad idea, and it will not solve the problem. Now it is up to the City Council to decide whether to proceed with that option.
The persistent toxic algae blooms are the result of excessive nutrients available in the lake sediments which feed the thriving population of cyanobacteria, also known as “blue-green algae”. The main nutrient responsible for the blooms is phosphorous, which is a naturally occurring element, but which exists in Waughop Lake in excessive amounts.
Fort Steilacoom Park was formerly used as a farm, operated by patients and staff of the nearby Western State Hospital from the late 1800s to 1965. Many of the barns are still standing, and are now historical landmarks. The farm was started as a means of growing food for the patients and staff, but also took on the mission of serving as occupational therapy for the patients who worked on the farm.
By 1946, the farm was raising 800 hogs, producing 8 tons of pork a month; over 2,200 turkeys and domestic ducks; and 60,000 chickens, chicks in incubators, and flock of laying hens, ranging from 7,000 to 8,000 birds producing 4,000 to 6,500 eggs a day.
Part of the abundance of the farm was due to a discovery made in the 1920s, as detailed in the April 1930 issue of Scientific American magazine. One of the patients who was tending a garden plot was noticed to have much better production than other plots. The supervisors inquired with the patient about how he had achieved those results, and he revealed that he had gathered up some of the lake-bottom muck as a soil amendment after the water level had been lowered by the irrigation pumps.
The practice of using the lake sediments as a soil amendment was soon expanded to the whole farm after the staff realized the material was diffuse enough to pump through their watering system. But after a while, the staff realized that they were depleting this resource, and so they decided to replenish it. Hospital records show that waste products from farming, including manure from livestock barns, were dumped into the lake. The Hill Ward, built on a knoll just to the north of Waughop Lake, had a sewer pipe running straight down to the lake. At one point, a slaughter house was built on brick pilings over the lake with a metal grate floor, the better for the offal to just fall through into the lake.
This addition of farm waste to the lake explains the high phosphorous loads that still exist today. Since Waughop Lake is a “kettle lake”, with no streams for inflow or outflow, everything that is in the lake for the most part stays there. The phosphorous ions that get taken up by the algae get recycled by subsequent generations after the algae die.
The farm ceased operations in 1965, and a few years later the State leased the land to Pierce County to operate as a park (later leased to the City of Lakewood). The toxic algae conditions have persisted thanks to all of the farm waste products still left in the lake. In 2011, the Tacoma Pierce County Health Department (TPCHD) determined that the toxic conditions were bad enough to merit posting signs, closing the lake to recreational uses.
As a late bit of background, Waughop Lake was further harmed in more recent years because of a plumbing problem at nearby Pierce College. Because most of the college sits below the level of the Pierce County Sewer System’s lines on Farwest Drive, the college’s plumbing system was designed to drain to a collection point with a “lift station” located very close to Waughop Lake. From there, the sewage gets pumped back uphill to connect to the sewer main lines.
But that lift station was built with a cross connection such that if the lifting pump ever failed, the raw sewage would be diverted into the storm drain which feeds rainwater from the college’s roofs and parking lots into Waughop Lake. There have been documented episodes of raw sewage discharge into Waughop Lake in 2007, 2010, and most recently in December 2016, resulting in another “lake closed” sign posting.
Pierce College asserts that the cross-connection problem has now been resolved, and a redesign of the lift station is underway. But the raw sewage which flowed into Waughop Lake is still there.
The blue-green algae which are causing the toxic problems in Waughop Lake are one of about 20 different species of microscopic life that are natural in our area’s lakes. Other area lakes like American, Gravelly, and Louise have these algae to some extent, but do not have the same nutrient loading that Waughop Lake has, so their levels are much more muted.
Phosphorous is a “limiting nutrient”. Other nutrients are also needed for the algae to live, but they are naturally abundant and thus not the limitation to algae population growth. Adding more phosphorous makes it easier for the blue-green algae to thrive and reproduce. A sudden addition of nutrients can bring a “bloom”, as algae feed and reproduce like crazy. Then as the bloom exhausts the available nutrients, the algae start to die, causing a secondary bloom in the bacteria which eat the dead algae. Those bacteria consume oxygen in the water, which can create an anoxic condition, killing fish in the process.
Blue-green algae have a unique adaptation, in that they can control their buoyancy. So when the sun is shining, they can float up to near the surface of a water body and absorb more sunlight for photosynthesis. They can also descend down to the lower part of the water column if they need to gather more nutrients. So in a shallow lake like Waughop, they find ideal conditions for growth.
Cyanobacteria can produce a toxin known as microcystin. It is taken up by the liver in fish and mammals, where it interferes with normal liver functions and can cause liver damage. In October 2004, a dog died after drinking algae-infested water from Lake Steilacoom. Exposure to bare skin can reportedly cause a rash and other irritation, although there have not been any confirmed reports of humans dying merely from skin exposure.
The way to keep toxic algae from being a problem is to limit the availability of phosphorous and other nutrients to the algae, thereby limiting their populations. Lakeside property owners are routinely advised to refrain from adding fertilizer to their gardens near the shoreline.
But it is a lot harder when the phosphorous is already in the lake, and has no way to get out. To keep the algae from having access to the phosphorous, it must either be removed from the water body or made otherwise unavailable. Removal can take the form of dredging, either hydraulically (pumping) or mechanically (scooping), or some combination of the two. Wet dredging is the method that the hospital farm staff used from 1927 until the farm’s closing in 1965.
One way to make phosphorous unavailable to the algae is by binding it up with some other chemical. The two most common chemicals for this purpose are alum (short for aluminum sulfate), and calcium hydroxide.
Alum is the more common approach favored by lake maintenance companies (who get paid to apply it, and then reapply it, so it is little wonder that they favor it). The chemicals are typically applied from a specially outfitted boat or barge as a wet spray. As the aluminum sulfate sinks slowly to the bottom, phosphorous binds preferentially to it, thereby taking the phosphorous out of the water and sinking the new compounds to the lake bottom. In a deep lake with a lot of soluble phosphorous in the water, this can be an effective treatment, at least for a while. But in a shallow lake, with a high phosphorous loading within the lake-bottom sediments, it is rather ineffective because it cannot bind with all of the phosphorous that is available to the algae. And eventually the alum-bound phosphorous can shake those bonds, and become available again.
Alum was used in 2008 in Wapato Lake in Tacoma, with disastrous results because the application was mishandled, resulting in a big fish kill. Because the effect of alum on binding up phosphorous is only temporary, it has to be repeated in subsequent years, and so Wapato Lake will have another treatment in 2017.
Green Lake in Seattle has also seen alum use, which is supposed to last 10 years. The 2004 application was determined to have failed prematurely, with toxic scums returning by 2011 which exceeded “safe” levels for microcystin. Another treatment was just done in 2016.
An experimental treatment of Waughop Lake with calcium hydroxide was done in 2008. It showed no lasting effect on reducing toxic algae levels.
In part 2 tomorrow, I discuss the regulatory issues involved with these treatment options.Print This Post