June Rainfall Overwhelmed Experiment In MIll Pond

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Heavy rains and a river of muddy, polluted runoff water that flushed into Mill Pond in Water Mill in June have cast a shadow of doubt over whether or not a much ballyoood “treatment” of the pond to battle algae blooms is working as well as it was supposed to.

For many years now, by mid summer, algae blooms would normally transform the water of Mill Pond into something more closely resembling split pea soup than a once healthy lake. When 100,000 pounds of a mineral compound, known by its commercial brand name, Phoslock, was spread across the lake in mid-April, proponents of the plan said they expected the lake’s waters to quickly clear and to remain at least relatively clear as the summer season went on.

Phoslock was supposed to chemically bind to the phosphorous in the lake bottom, preventing it from mixing in the water column where it feeds algae blooms, especially those of a species of blue-green algae that produces toxins that can kill fish and other aquatic life.

But today, Mill Pond’s waters are once again green, clouded and thick with algae.

Scientists working for the Town Board and the Southampton Town Trustees said it appears the amount of the toxic blue green algae had been reduced thus far, a sign that the Phoslock may have been having at least some of its desired effect.

But water samples taken in mid June, before and after a period of five days when more than 8 inches of rain fell, showed a spike immediately afterward in algae blooms, including the blue-green species that have plagued the pond for year. The blue-green algae bloom dissipated about one week after the last of the heavy rains, on June 13. But blooms of green algae, which are not toxic but can also be harmful to aquatic life, have persisted.

Nonetheless, the biggest proponents of the Phoslock treatment, which have already cost the town some $250,000 and is on tap to cost another $200,000 next spring, are optimistic.

“The Phoslock is working great,” insisted Trustee Fred Havemeyer. “Blue-green algae has virtually disappeared from the lake. There has been virtually no cynobacteria, only at negligible levels.”

Mr. Havemeyer said that the scientists monitoring the pond for the town since the Phoslock application are optimistic that the compound will continue to draw phosphorous out of the water, even that flushed into the pond by the June rains, as it settles to the bottom, where the granules of the compound are.

“That rainfall put a tremendous amount of nutrients over the top of the Phoslock,” Mr. Havemeyer said. “The Phoslock was put in in granules so that it would settle at the bottom of the pond and capture the phosphorous and keep it there. Now you have this new infusion. As that settles to the bottom over the next month to two months and bonds to the Phoslock, I think we’ll see the lake clear.”

Some are not so optimistic.

Dr. Chris Gobler, a professor at SUNY Stony Brook’s School of Marine and Atmospheric Sciences, who has been conducting water testing in Mill Pond for several years and has taken samples since the Phoslock was introduced, said that the pond’s makeup compared to past years is not all that different.

“We still need to sit down and look precisely at the data but the levels of algae are not that different from last year at all,” he said. “There are cynobacteria blooms in there. There are cynotoxins again. And you don’t need a lab to tell you the water is turbid and green.”

Dr. Gobler said that if the Phoslock had worked as expected there would have been a marked clearing of the water shortly after the compound was deposited in the lake, which didn’t happen.

But Dr. Gobler said it is far too early in the first-of-its-kind experiment, followed by unusual circumstances, to call the effort a failure.

Town Councilwoman Christine Scalera said she got the impression from the analysis of water sample data by Lee Lyman, a lake specialist hired by the town to track the pond conditions based on bi-weekly water sampling throughout the summer and fall, that the experiment has been working out largely as expected.

She noted that what the “bump in the road” in June showed everyone, was that a town effort to reduce stormwater runoff flowing down Deerfield Road needs to moved forward as quickly as possible. Town engineers have been working on plans for a large scale series of vegetated swales and wells along the sides of Deerfield Road to slow and capture polluted rainwater running off farm fields, lawns and roadways before it gets to the pond.

Water Mill resident Steve Abramson, who was one of the first and most vocal proponents of the Phoslock experiment, said that the stormwater abatement effort needs to be made a top priority, for both the town and the dozens of private homeowners who live uphill of Mill Pond.

“Fred [Havemeyer] is going to be talking to homeowners about containing stormwater on their properties, as required by law,” Mr. Abramson said. “Joe Gergela, from the Farm Bureau, told me it’s been two years since state laws required that all farm fields contain their stormwater, which hasn’t happened here.”

Supervisor Anna Throne-Holst said that Tom Halsey, a farmer whose field looms over Mill Pond, has recently installed an intricate capture and natural filtration system along the borders of his land, which the town’s engineers are using as a possible model for how the town will proceed along the roadway.

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