The Water Quality Improvement Projects Advisory Board has received a report that the average level of nitrates in test wells around Shelter Island is 2.8 milligrams (mgs) per liter, while in the Center, the average is 5.78 mgs per liter.
Town Engineer John Cronin — who presented the report with Andrei Oraseanu, his department’s intern — lives in the Center and said his drinking water averages about 8 mgs of nitrogen per liter of water. The level considered potable for nitrates is 10 mgs per liter of water.
Water Quality Board Chairman Mark Mobius calculated that if the board recommended concentrating its funding for nitrogen-reducing septic systems in the Center, it would take at least five years just to reach a point where the problem wasn’t increasing at the rate of one percent per year. To begin to lower the nitrate level in the Center would take at least 10 years, Mr. Mobius estimated.
The Center’s water is much worse than other parts of the Island because of the concentration of public buildings, Mr. Cronin said, pointing to Shelter Island School, the American Legion Post/Recreation Center, the Library, Center Firehouse and several town buildings.
The school has been using filters and another well to keep its drinking water potable, Mr. Cronin noted, but having more nitrogen-reducing septic systems throughout the Center would be the start of a solution.
A new septic system for the Legion Post and part of the school will help the situation somewhat, Mr. Cronin said, but the other public buildings are not slated for new systems.
It would take 163 nitrogen-reducing septic systems in the Center to reduce nitrates by 10 percent and 615 systems to reduce nitrates to the 2.8 mg. per liter level, according to the data compiled by Mr. Oraseanu and Mr. Cronin.
Mr. Cronin and Mr. Oraseanu took their research to the Suffolk County Department of Health Services and also met with United States Geological Survey (USGS) representatives to discuss this study. County officials agreed to provide more than 5,000 water tests they have conducted here, redacting names and specific addresses, to give the town engineer more data.
The USGS officials agreed that the model Mr. Cronin and Mr. Oraseanu created provides a “pretty good estimate of what’s going on,” Mr. Cronin said.
Drinking water is not an issue for 90 percent of the county since the Suffolk County Water Authority (SCWA) provides drinking water. If the SCWA has a problem with one of its wells, it can blend the water from other wells to decrease the problem, which is not something Shelter Island can do. Most of the Island isn’t connected to SCWA, although the water authority has made inroads in Dering Harbor.
In many areas of the nation, precipitation would decrease nitrates. But in the northeast, acid rain falls. This means more nitrates in the water, not less, Mr. Cronin said.