Mill Pond Experiment Shows Some Success, But Future In Doubt

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The Southampton Town Trustees released results of water sampling in Mill Pond last week that seem to show an experimental chemical treatment of the pond has greatly lowered levels of phosphorous, a pollutant that feeds the algae blooms that have choked the pond’s waters for years.

The Trustees and their consultants said that the results from the water sampling show that the experimental compound added to the pond last spring, known by its brand name, Phoslock, is working as expected, despite two extraordinarily heavy rainstorms last summer that flushed additional pollutants into the pond.

But despite the extraordinary circumstances, some Town Board members say that a second application of Phoslock to the pond, slated for April, should perhaps be put on hold—or dropped altogether—to make sure the town is not wasting money.

Supervisor Anna Throne-Holst said that results from the Phoslock application have been unsatisfactory, even in light of the two heavy rainfalls, and that it may not be in the town’s best interests to fund the $200,000 cost of a second application.

Ms. Throne-Holst said this week that town attorneys are reviewing the contracts signed with SePro Corp., the company that sells Phoslock and conducted the experimental application last spring. She said the contracts contained guarantees of success that the experiment has not produced, and that should either free the town from proceeding with the second application or should substantially reduce the town’s financial contribution for that application.

“Would we love to find a silver bullet for all of this? Of course—but the question then becomes: Is this stuff a silver bullet, and how much does it cost?” Ms. Throne-Holst said. “It’s an experiment. At what point do you consider it a reasonable cost for an experiment?”

Town Councilwoman Christine Scalera, who helped bring the Town Board and Town Trustees together on the deal for the first application last spring, said that she thinks the second application should be put off for a year to allow more water testing to be done to ensure that the scientific evidence for the use of Phoslock is still there, in the wake of the rainfall events that brought more than 8 inches of rain in five days in June and another 4-plus inches in just two days in September.

“I would prefer to put off the second application of Phoslock at this point,” Ms. Scalera said. “Because of the heavy rainfalls, they need to reevaluate the nutrient budget. I think we have agreed we want to test the water for another year before we do a second sampling, which also gives us a chance to have some of the Deerfield Road stormwater abatement in place.”

This spring the town will conduct the first of two projects over the next year planned for the Deerfield Road area to reduce the amount of harmful stormwater runoff that reaches the pond.

Heavy rains flood farm fields to the north of Mill Pond and carry large amounts of silt and soil laden with chemical fertilizers applied to crops into the pond. Fertilizers are largely made up of phosphorous and nitrogen, both compounds that can feed algae blooms.

Town Trustee Fred Havemeyer, who spearheaded the Phoslock experiment with a coalition of Water Mill residents, said this week that he hopes the results from the most recent testing show the Town Board members that the Phoslock clearly worked as expected, even if the results weren’t as immediate as hoped.

“That the phosphorous has been cut in half from last spring is really remarkable given the load [of polluted stormwater] that went in there this summer,” said Mr. Havemeyer, who is retiring from the Trustees at the end of the year. “It’s clear that the Phoslock has worked. A second treatment and some small dress-up applications, and it should be good for 10 years.”

The first treatment of Phoslock cost $250,000, of which the Town Board paid $200,000, using money donated to the town by a Water Mill homeowner in exchange for being allowed to alter the shoreline of a property on Mecox Bay. The Trustees paid the other $50,000.

Phoslock is a clay-like mineral compound developed by scientists working for the Australian government to address algae blooms in reservoirs there. The granules of clay bind to phosphorous in the water as they sink to the bottom, removing the phosphorous from the water column where it can feed algae blooms in warm months.

Engineers from SePRO have said it would likely require two large scale applications of Phoslock to capture the pond’s phosphorous, followed by annual small applications to accommodate for additional amounts of the nutrients that would enter the pond through rainfall runoff and groundwater tainted with the leftovers of decades of farm cultivation in the area and residential septics.

Consultant Jim Walker, who coordinated the Phoslock application for the Trustees, said that the latest water sampling does appear to indicate that, after the pond settled from the two heavy rainfalls, the Phoslock was successful in removing phosphorous from the water.

Mr. Walker said that water sampling in Mill Pond between 2005 and 2009 showed an average phosphorous level of 145 parts per billion. The most recent samplings show just 56 parts per billion.

“The end result is, at the end of the year, we have a good reading, half of what it was in April,” said Mr. Walker, who works for Inter-Science Research Associates in Southampton Village. “Now that the pond has settled down and we’ve gotten away from those rainfall events, the Phoslock is doing its job. Without the storm event in June, I think we would have had spectacular results in August.”

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