Wednesday, March 20th, 2013
By Nancy Allen
Alum impact over by summer's end
Expert: 2012 treatment staved off blooms
GRAND LAKE - Last year's alum treatment on Grand Lake reduced phosphorous levels by about the same amount as in 2011, but those levels rebounded much more quickly.
A report released this week on last year's treatment showed phosphorous levels at the end of the summer were as high as they'd been prior to treatment in April, report co-author Harry Gibbons of Tetra Tech Inc. said. The main reasons: heavy spring rain brought in phosphorous and then a summer drought concentrated it.
Had the lake not received alum in the spring, the lake's toxic blue-green algae blooms would have been much worse, Gibbons said. Alum deactivates phosphorous, the main food of the lake's toxic, blue-green algae.
"Phosphorous levels would have been much higher, 50 to 100 percent higher," he said Tuesday. "The algae was less than what you would have had, and we haven't had the really, really bad (algae) like we did in 2010, so it has controlled the quantity and type of algae to a certain degree."
Gibbons said the alum did what it was supposed to - it reduced phosphorous levels and lessened algae blooms.
The results are not enough to convince the state to continue the expensive treatment.
The state on Tuesday officially announced it will not fund a third alum treatment this summer. The focus now will be on keeping phosphorous from entering the lake by working with local farmers to implement nutrient management plans, which will help reduce runoff, Bethany McCorkle, a spokeswoman for the Ohio Department of Natural Resources, said.
"We will also continue our multi-faceted approach to improving the water quality through our dredging operations, rough fish removal, lake leveling and the inland creation of a wetlands as other effective ways to reduce the source of phosphorus entering the lake," she said, adding alum was a single element of an overall plan to combat algae.
The state spent $8.4 million for alum treatments the last two years. Some have called that a waste of money.
Milt Miller, manager of the local Lake Restoration Commission, disagrees.
"So many people have taken issue with the alum treatment, but we feel confident, based on the science and what happened in 2010, it served its purpose as a temporary short-term tool while we explored other things in the watershed and other technologies," Miller said. "We knew going in alum was not in fact a long-term solution."
The LRC in recent years has raised thousands of dollars to test new technology and devices aimed at improving the lake's water quality.
The report says in-lake treatments such as alum must be combined with efforts to reduce sediment and nutrient sources flowing into the lake. All of these efforts must be coordinated and tracked to ensure proper sequencing, location and design, it continues.
Even with significant reductions in external phosphorous, lake phosphorous and associated algae blooms may remain high for the next three to four decades, the report says. This is because the phosphorous in the sediment of shallow lakes keeps recycling and feeding the algae.
Most of the phosphorous that enters Grand Lake runs off farmland, the largest land use in the 58,000-acre watershed. Watershed farmers are now required to have nutrient management plans - a formal document that tells where, when and in what amount to apply nutrients without causing pollution - and must follow new rules on when they are allowed to apply manure.
Toxic algae, also called cyanobacteria, is common in many water bodies and can grow thick in waters with lots of phosphorous from manure, commercial fertilizers and sewage, often washed into streams by rain and melting snow.
The state has issued varying water advisories for unsafe algae toxin levels the last four summers. The worst was in 2010 when a different, freakish algae coated the lake and the public was warned to have no contact with the water. Last year's advisory warned the elderly, very young and people with compromised immune systems not to swim or wade in the water.
Gibbons said the reason phosphorous levels rebounded so quickly last year was because more of it flowed into the lake with heavy precipitation in late 2011 and early 2012 and then last summer's drought increased the phosphorous concentration. The already shallow lake had 23 percent less volume, which, combined with windier conditions, re-suspended more phosphorous and algae in the water column, the report says.
Miller said he can't help but speculate what the lake's condition would be had it received what was considered a full dosage of alum in the entire 13,500-acre lake. The report says the lake received 25 percent of an optimal treatment.
The state opted for lower-dosed, smaller treatments the last two years due to the price tag for the full treatment - $20-$30 million.
"We know as evidenced by the science the positive effects of alum in the two treatment years as a partial dosage," Miller said. "We will always wonder what could have been had, we been able to have a full lake application."
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Colder, snow showers
Colder, snow showers