By Richard L. Gaw
For the 25 residents of Somerset Lake who attended Monday night's New Garden Board of Supervisors meeting to hear a presentation by environmental consultant Frank Browne, the news they received was shocking. Somerset Lake, the man-made body of water in the middle of their high-end residential alcove of Landenberg, is knee deep in the big algae.
Sharing the results of his three-year study of the lake and its nearby watershed, Browne, a professor at Villanova University, said that Somerset Lake is exceedingly high in phosphorous and chlorophyll A, and its high level of blue-green algae is giving off dangerous toxins that can be harmful to both humans and pets at its current levels, with the potential to be fatal.
Browne's 45-minute presentation, sponsored by the Somerset Lake Service Corporation and entitled, "Lake and Watershed Management Plan for Somerset Lake," shared the findings of when the lake was sampled during the summer of 2011. In samples collected in June, July and September of that year, it was discovered that the lake is "hyper-eutrophic," meaning that it is exceedingly high in sediments and nutrients caused by erosion and runoff from nearby mushroom farms, developed areas, roadways and poorly vegetated areas. Browne said the lake was "worse than 90 percent" of the lakes in the United States, and "potentially greener than all the lakes in the country. It's supersaturated with algae, and its content of algae gets worse as the lake gets deeper, thus cutting off oxygen for fish, who end up needing to live on the top of the lake," he added.
"Nature has a natural tendency to fill in its lakes, in order to become greener," Browne said. "Eventually, what a lake wants to go to is a swamp, and given time and erosion, a lake will become a forest. It is a natural process that could take hundreds of years. Then man comes along and he accelerates that process."
Browne said that 54 percent of the watershed surrounding Somerset Lake is "in bad shape, and that number is unusually high" for a body of water that size. With the help of overhead visuals, Browne spelled out not only the difficulties with Somerset Lake and its surrounding watershed, but also recommendations for both in-lake and watershed restoration.
Among his ideas for improving the lake, Browne said that the excessively high amount of blue-green algae could be controlled by the use of algaecide treatments during warm-weather periods, or by the use of a diffused air bubbler aeration system that could supply oxygen to the lake. The Somerset Lake Corporation, he recommended, could install floating wetland islands to reduce phosphorus concentrations in the lake. Dredging the lake of its sediments and nutrients could also be an option, Browne said, but one that would cost up to $1 million.
Browne also recommended that the township create a stormwater utility in the township that can provide long-term control of stormwater throughout the watershed near the lake. Severely eroded stream banks in the watershed, the largest source of sediments and nutrients in the lake, should be stabilized and restored using bioengineering stream bank restoration methods, Browne suggested, or retrofitted with stormwater controls that would protect water quality.
Browne also recommended that the township work with mushroom farmers in the watershed to explore possible operational improvements to reduce stormwater runoff into the lake. The township, he said, could also supervise the demolition of abandoned mushroom houses on Reynolds Road and Sunny Dell Road and turn these areas into green space.
In terms of the role that nearby homeowners can play, Browne recommended that they install rain gardens, plant shoreline vegetation and low bushes, and that those living on the lake's edge should leave a five-foot no-mow buffer between the grass and the lake.