Lake Phosphorus Reduced 55 Percent
ST. MARYS — A federal report released Friday indicates that last year’s alum application reduced the internal phosphorus load of Grand Lake St. Marys by 55 percent — a revelation one local lake official calls a success for the lake.
The U.S. EPA report showed the application, the second for the lake since 2011, was effective at reducing phosphorus in the lake. Reducing the internal load of phosphorus has been key in the battle to heal the lake in recent years because it fuels the growth of algae — which can bloom and then result in the release toxins into the lake.
“To no one’s surprise, the report revealed that a significant amount of phosphorus was inactivated as a result of the alum treatment, and we are satisfied with the results, but this was always one part of a multi-faceted, multi-year plan for the lake and for the watershed,” Ohio EPA Director Scott Nally said in a news release. “The alum treatment was a significant investment that had to be made to provide the time necessary to make sure we could implement the other comprehensive, long-term practices and plans we needed to have in place to be successful.”
Since the bloom of 2010 — which effectively caused the lake’s closure — the state has allocated more than $8 million for alum applications. There will not be a third application for Grand Lake St. Marys — news local lake officials have acknowledged since late last year.
“We have accomplished a lot of work in the lake and in the watershed in the last two years, and we remain dedicated to the health and success of Grand Lake St. Marys,” ODNR Director James Zehringer said in a news release. “This problem wasn’t created overnight, and it won’t be fixed overnight either. The alum treatment was a single element in our overall plan to combat algae in (Grand Lake St. Marys), and we will continue to work within the watershed to improve the lake’s water quality.”
The alum has long been viewed as a short-term solution to keep the lake open as local officials worked on a long-term, multi-pronged strategy. Grand Lake St. Marys Restoration Commission Manager Milt Miller said the alum did exactly what it was supposed to the past two years.
“Clearly we consider it a success because we had an open lake,” Miller told The Evening Leader. “We feel it played a large role in that, and here’s a thing that is immeasurable that we have asked ourselves — what would the lake have done if alum was not introduced?”
This year, lake officials plan to focus on three areas — aeration, circulation and dredging. Given the shallow depth of Grand Lake St. Marys, proper aeration and circulation can be difficult to achieve and sustain.
“There is no one silver bullet that is going to cure the lake in one swoop,” Miller said. “We have to have a multi-pronged attack.”
Another tool in the box to help heal with lake is the recreation of wetlands. Construction will soon start on a 90-acre wetlands that will have several benefits for Grand Lake St. Marys.
“The wetlands will provide us with a 90-acre site to pump to, which is more capacity than the state has ever had in terms of a spoil site,” Miller said. “The value-added is that once the pumping is done, we will come in and plant wetlands plants and re-establish the wetlands.”
Back in the 1930s, the lake was surrounded by what is believed to be 4,000 acres of wetlands, predominately on the south side of the lake.
“That’s what Mother Nature wanted to keep itself healthy,” Miller said, noting they have aerial photographs that depict the wetlands. “That’s now our challenge to bring those back.”
Dredging also will help remove internal phosphorus loads from the lake. During the dry summer months, dredging is most effective because many of the lake’s tributaries have dried up.
“In the summer, the science has told us that most of our phosphorus loads are produced by the bottom of the lake,” Miller said.