Saturday, July 10th, 2010
Alum alone won't cure Grand Lake
By William Kincaid
GRAND LAKE - Alum treatment alone will not be enough to ensure the long-term sustainability of Grand Lake, the report says.
Aerators in the lake and best management practices throughout the entire watershed also are needed. Dredging is not the answer, according to the report.
The report was created by consultant Tetra Tech for Ohio and U.S. EPA officials. The Ohio EPA had no comment on Friday as the report has not been fully analyzed, according to a spokeswoman.
"To address this environmental decline and poor water quality, a variety of methods of providing both in-lake treatment and external load reductions are needed," the report states. "Ultimately, phosphorus availability must be substantially reduced to limit the primary conditions in Grand Lake St. Marys."
Tetra Tech recommends a five-year action plan that begins with educating landowners, farmers and homeowners about best management practices. Some of these practices include nutrient management plans, conservation tillage, grazing land protection, filter strips, cover crop, conservation easements and restoration of riparian buffers.
The consultants also recommend conducting two alum demonstration projects during the first year - one using alum treatment and the other using a pretreatment of peroxide followed by alum.
Alum has been shown to cause phosphorous to coalesce and drop to the bottom, holding pollution in place. Phosphorous feeds the blue-green algae that has bloomed excessively on the lake this year.
"Each of these two approaches should be used in separate (areas) that are between 40 and 80 acres," the report states of the alum treatments. "The (areas) should be closed off with curtains (barriers) to prevent, or at least minimize, water exchange with the open lake."
Analysis should follow.
Also, the report says aerators should be placed strategically in channels and bays to improve dissolved oxygen levels, to help reduce the amount of organic materials in the sediment and to keep the water circulating to reduce odor.
"The estimated cost to aerate the 2 percent of the lake surface that would benefit from aeration is approximately $12.7 million plus annual operation and maintenance of $200,000," the report says.
The second and third years of the plan should include a focus on wide scale lake treatments and reduction of external phosphorus loads, according to the report.
If an alum demonstration proves that the chemical is effective in reducing internal phosphorus loading and improved water quality, a full scale application of alum to the lake should occur.
At a past Lake Improvement Association meeting, Ohio EPA Director Chris Korleski said alum treatment of the whole lake could cost millions of dollars.
Also, depending on the success of the previous year, aerators should continue to be placed around the lake.
During the fourth and fifth year, Terra Tech recommends comprehensive lake monitoring, continued reduction in external loading and stabilization of the lake's shoreline.
As for dredging the lake, the report advises against it. Dredging is the most expensive lake restoration technique and too high (in cost) for serious consideration, the report says.
"Therefore, although dredging should be employed in strategic locations, such as at the mouths of large tributaries where there is significant sediment/nutrient building, it is not recommended for full-scale application," the report says.
The report's overall action plan is intended to improve water quality and meet the following restoration goals identified by Ohio EPA:
• Improve the lake from its present hypereutrophic and unhealthy state.
• Greatly reduce harmful algae blooms be inactivating internal nutrients.
• Restore and maintain water quality to ensure safe human recreation.
• Greatly reduce fish kills caused by insufficient dissolved oxygen levels.
• Reduce external nutrient and sediment loads into the lake.
• Improve local land use management to protect the lake.