A state-sponsored alum treatment at Grand Lake St. Marys in June successfully reduced the intensity of harmful algal blooms in the lake this summer, according to a recent report by a U.S. EPA environmental consultant, Tetra Tech, Inc.
“I think we may have prevented a recurrence of the severe and damaging bloom of 2010 by reducing the phosphorus readily available to the cyanobacteria,” said Tetra Tech’s Dr. Harry Gibbons, author of the report. “This was like a multilayer cake and the alum prevented the frosting from being put on this year.”
The report revealed that the alum treatment exceeded expectations by reducing phosphorous levels in the center of the lake by 56 percent. A 50 percent reduction was the target for the partial treatment of the middle 4,000 acres of Grand Lake St. Marys.
The report also provides encouraging data for areas of the 13,000 acre lake not directly treated by alum this summer. Phosphorus levels decreased between 20 and 30 percent throughout the lake once the alum treatment was complete.
“These are positive results that exceeded our expectations,” Gibbons said.
The alum treatment also had a direct effect on water quality which improved recreational opportunities at Grand Lake St. Marys this year. Last year, events at the lake had to be cancelled due to poor lake water quality and toxic conditions.
The State of Ohio made Grand Lake St. Marys a priority in January when directors from the Ohio Environmental Protection Agency, the Ohio Department of Natural Resources (ODNR) and the Ohio Department of Agriculture all visited the lake the first week of Ohio Governor John Kasich’s administration.
“The previous summer’s bloom at the lake negatively impacted the regional economy of Grand Lake St. Marys,” said Ohio EPA Director Scott Nally. “Governor Kasich committed from the outset to having his cabinet work closely with the local community in developing an action plan to tackle this issue. The alum treatment was one of the tools we used and it clearly improved the water quality at the lake.”