Town Engineer John Cronin didn’t mince words: “The bottom line is that this is not a situation that’s going to get better, it’s going to get worse without some radical changes.”
He was speaking about the Island’s septic systems and cesspools, reporting to the Town Board work session Tuesday on a conference he attended last week on the subject.
The problem is dangerous pollutants, especially nitrogen compounds.
Mr. Cronin began by making a distinction between septic systems and cesspools. A cesspool is basically “just a hole in the ground,” he said, and a septic system has a tank and “leaching pools.”
But cesspools and septic systems are not capable of de-nitrification, Mr. Cronin reported, so neither one does much of anything to stop the flow of nitrogen compounds that poisons drinking water and surrounding surface waters such as ponds and bays.
Local and county officials, university researchers and representatives from nonprofits attended the conference held March 25 in Nassau County. The University of Rhode Island, which has taken a lead, Mr. Cronin said, in regional studies of the situation, has done research showing that these home sanitary systems do little more than provide a partially clarified effluent. This effluent not only contains nitrogen, but also phosphorus compounds, pathogens, personal care products and drugs.
The typical septic system removes only about 15 percent of nitrogen, while the federal Environmental Protection Agency requires that drinking water standards have nitrate levels of 10 milligrams or less per liter.
“Many people on Shelter Island are drawing water from the aquifer, and many people are getting OK water,” Mr. Cronin said. But many parts of the Island, he added, have nitrogen in drinking water higher than that value of 10 milligrams per liter.
“Percolation rates” were discussed, or how quickly water will move though soil. In sandy soil, Mr. Cronin said, water moves about four inches per hour, while soil with more silt and clay takes about two inches per hour.
“If you take an average of three inches per hour, where we are relative to groundwater is the effluent from septic systems can find its way into the ground water in a relatively short period of time,” Mr. Cronin said.
In Southold, some studies have found it takes only 90 minutes.
“Property owners’ management of existing systems has been pretty much non-existent,” Mr. Cronin said, with many people taking a “set it and forget it” attitude. “Research has proven that this is no longer valid thinking.”
The first step is to develop some current data, Mr. Cronin advised, which can begin by looking into Building Department files on the age and maintenance records of septic systems. Then meaningful discussions have to take place.
Supervisor Jim Dougherty agreed with Mr. Cronin that the report was “an eye opener” and suggested the topic be included in future work session agendas.