ST. MARYS — Results of an alum test project in April on three locations within Grand Lake St. Marys yielded results that could bode well for the lake.
Ohio EPA spokesperson Dina Pierce said results of the test project, which were used to help calculate the dosing for June’s 4,500-acre application, showed liquid alum was successful at reducing phosphorus levels at the state park bay and Windy Point Marina the first two days. However, heavy rains in the spring before the test proved too much for the granular alum to overcome at Kozy Marina and also impacted the liquid alum.
“Spring is always a wet time of year and it was heavier than normal and there was high water, which pushed more phosphorus down stream,” Pierce told The Evening Leader. “So between a lot of sediment at Kozy Marina and the wet spring, they couldn’t get an accurate evaluation of the granular alum.”
The liquid alum caused an 81 percent reduction in phosphorus near the state park bay and a 90 percent reduction at Windy Point Marina. Pierce said these statistics showed liquid alum, if applied under the correct circumstances, can be effective.
“Then we got a couple of big rains and that really pushed a lot of phosphorus and sediment into the lake,” Pierce said. “That overwhelmed those experiment areas.”
Pierce said officials took lessons learned from the pilot project and applied those to the June dosing.
Initially, state officials wanted to dose the entire lake with a low dose of alum but they opted to concentrated on the middle of the lake. That portion contained the highest concentration of phosphorus.
“What we learned was that the info led us to rethink what we were going to do with that treatment in June,” Pierce said. “We are happy with what we have seen so far out there and we are still in the middle of peak algae season.”
While officials lack data to back up the successfulness of the June alum dosing, Pierce said the improved water quality of the lake cannot be called into question. Microcystin levels have hit a high in the 40 parts per billion range — down from a high of 2,000 ppb last year.
“I think if you go out there, I think it’s had some benefits because if you look at the similarities in weather — heavy rains followed by a hot, dry summer, that’s what algae needs to grow,” Pierce said.
“It (alum) is not going to stop it but I think we are seeing that it’s not as bad as this year as it was in 2009 or 2010.”
In a memo issued by Tetra Tech regarding the project, the firm noted a whole lake alum treatment at the right time of year, early spring, would net a massive reduction of approximately 14,500 pounds of phosphorus and 15.9 million pounds of wet algae from the water column of the lake. Pierce said officials are still working on compiling the data from June’s application.