About 5 percent of what’s going directly into the aquifer every day is sewage.
That’s the word from Town Engineer John Cronin, who went before Tuesday’s Town Board work session to stress greater efforts to replace aged septic and cesspool systems with newly develop technology.
Because of the many old systems on the Island, Mr. Cronin said there are 50 to 60 milligrams (mg) of nitrogen in every liter of waste water. According to U.S. Environmental Protection Agency standards, a limit of 10 mg of nitrogen per liter is the goal of new technologies.
Suffolk County’s new septic systems, Mr. Cronin said, can reduce nitrogen content to 19 mg per liter. The goal is to reduce it to the 10 mg per liter.
On a typical summer day on Shelter Island, 10,000 residents produce 700,000 gallons of septic system wastewater that goes into the aquifer, Mr. Cronin said. He compared that to 17 residential swimming pools of wastewater flooding into the aquifer daily.
Worst among the affected areas in town is the Center, where there are a lot people at the Shelter Island School, the American Legion Hall, the library and Town Hall.
There are efforts under way to improve water quality, Mr. Cronin said. A project started with grant money at the American Legion Hall is now being shared with the school so both buildings will have an upgraded septic system, Mr. Cronin said.
“We’ve made some remarkable progress in getting grants,” he added.
He also pointed to the Sylvester Manor project where ground was broken last week for a state-of-the-art “clean water system.”
Major contributors to high nitrogen levels include not only insufficiently treated wastewater from aged septic and cesspool systems, but from lawn and agricultural fertilizers. Nitrogen compounds in levels that are too high in coastal and inland waters negatively affect some organisms upsetting the aquatic habitat balance, Mr. Cronin said.
Using new effective systems would be a $40 million undertaking just on Shelter Island and $9 billion throughout Suffolk County, the engineer estimated.
But the cost doesn’t stop with just the installation of a new system, Mr. Cronin said. There’s an approximate $1 million annual cost to maintain them, he said.
If Shelter Island voters in November approve use of up to 20 percent of the Community Preservation Fund — money collected by a 2 percent tax on real estate purchases now used solely for land preservation — for water quality projects, that could offset some of the cost, he said.
By way of lowering expenses, he noted the New York State Center for Clean Water Technology at SUNY Stony Brook is researching less costly technologies that would achieve 10 milligrams of nitrogen per liter, have a 30-year life and be priced at as little as $10,000, instead of the estimated $20,000 to $30,000 for other systems on the market.