By Don Russell, Lakewood
This paper describes the likely biological response of Waughop Lake as a result of the discontinuance of untreated sewage discharges from Pierce College into the Lake.
Since the original plumbing of Pierce College’s sewage system and up until the winter of 2016-2017 there have been periodic discharges of raw sewage into Lake Waughop as a result of overflow of the sewage transfer station located at the toe of a slope midway between the college and Lake Waughop. This discharge was first noticed and photographed by Don Russell in December 2007 and resulted in the posting of the Lake by the Tacoma Pierce County Health Department. The cause was ascribed to a construction mishap occurring on campus at that time.
No further investigation of this recurring phenomenon was done until the winter of 2016-2017 when it was confirmed that the sewage lift station was discharging raw sewerage into the Lake.
Don Russell began monitoring water quality in Waughop Lake as a volunteer in 2009 under the supervision of the Tacoma Pierce County Health Department who had received a grant from the Center for Disease Control and Prevention. The purpose of this grant was to determine the severity of harmful algal blooms occurring in 30 lakes located in the Puget Sound Basin.
The CDC sponsored water quality/cyanobacteria toxin monitoring of Waughop Lake began during the summer of 2009 and continued through the summer of 2013.
During the summer of 2011Waughop Lake’s cyanobacteria toxin (microcystin) concentration was determined to be 25,200 parts per billion. The threshold above which a health hazard exists is 6 parts per billion. This resulted in the unprecedented closure of the Lake by the Tacoma Pierce County Health Department. As it turned out Waughop Lake was the most cyanotoxin polluted lake of all of the 30 lakes monitored during the five year CDC study.
At the end of the CDC/TPCHD sponsored monitoring of Waughop Lake the City of Lakewood contracted with the Pierce Conservation District to include on-going water quality monitoring of Waughop Lake. Don Russell was the Waughop Lake volunteer water quality monitor from 2014 through 2016. All during this time toxic cyanobacteria blooms were the summer time norm for this Lake.
Waughop Lake Management Plan
The Brown & Caldwell Waughop Lake study and Lake Management Plan was done during the 2015-2016 period when toxic algal blooms in Waughop Lake were still the predominate biological response of the Lake to nutrient pollution. The Plan recommended and the City Council approved an alum (aluminum sulfate) treatment to inactivate phosphorus believed to be emanating from Waughop Lake’s bottom sediments.
Unbeknownst to the Brown & Caldwell monitoring team was that raw sewage was being periodically discharged into Waughop Lake as a nutrient source thus its biological effect on Waughop Lake was not accounted for in either their study, findings or alum treatment recommendation.
The biological effect of the 2017 discontinuance of sewage discharge
The discontinuance of sewage discharge into Waughop Lake has resulted in its water becoming clear and largely devoid of toxic cyanobacteria blooms. However what has appeared is prolific growth of aquatic plants that foul the surface of the lake as noted in the above right hand photo.
The consequence of this change in the external nutrient loading of Waughop Lake
Alum treatments are administered to prevent nutrient (phosphorus) release from lake bottom sediments that foster cyanobacteria population growth to bloom proportions. Their applications result in significantly improved water clarity. In a shallow lake the usual biological response to an alum treatment and its water clarifying effect is prolific aquatic plant growth, such is now occurring in Waughop Lake. Apparently the cessation of sewage discharge into Waughop Lake has created the very condition that one expects after an alum treatment.
The consequence of excessive aquatic plant growth
The beneficial recreational (e.g., fishing, boating, swimming) use of Waughop Lake will be seriously impaired. When the fall die-off of the plant biomass occurs its bacteria decomposition in the lake may cause dissolved oxygen depletion and a fish kill. That which washes ashore will undergo bacterial decomposition that will create a foul odor that will affect all park attendees.
The cessation of raw sewage discharge into Waughop Lake has apparently changed its biological response from experiencing recurring toxic cyanobacteria blooms to now facilitating excessive aquatic plant growth. An alum treatment is effective in preventing toxic cyanobacteria blooms, but ineffective in preventing excessive aquatic plant growth. There are only three effective treatments for preventing excessive aquatic plant growth, i.e., annual harvesting, remove the sediment that fosters their growth or annual application of herbicides.