DEC: Residential septic systems not discharging waste into stream

Eight home septic systems investigated as possible sources of contamination of a Glen Cove beach are not discharging waste directly into a stream that feeds into Long Island Sound, the state has concluded after a monthslong investigation.

But the New York State Department of Environmental Conservation has not ruled out that seepage from septic systems at those properties or elsewhere is responsible for the contamination at Crescent Beach.

The DEC’s examination of the discharges is the latest of a number of investigations and studies by the state, Nassau County and the city of Glen Cove over several years that have reached dead ends in trying to determine the cause of high bacteria levels that have kept Crescent closed for swimming and bathing since 2009.

In December, the DEC identified the eight properties as potential contamination sources after a county-commissioned study found that 11 unpermitted pipes within a half mile of the beach were discharging water with elevated levels of coliform and enterococci — bacteria found in human and animal waste — into the stream.

The agency put nontoxic dyes in the properties’ septic systems to determine whether waste from the systems was ending up in the stream. The DEC also inserted specialized cameras in the unpermitted pipes to find out whether those pipes lead to septic systems.

The DEC investigation “has confirmed that there is no direct discharge from area septic systems to the stream,” the agency said in a statement.

But the DEC is still looking into whether faulty septic systems there or at other locations may be leaking waste that travels through groundwater into the stream. In May, the U.S. Environmental Protection Agency collected water samples from stormwater and groundwater discharge pipes that empty into the stream area for a DNA analysis to determine whether the coliform contamination is from human or animal waste, the DEC said. The DNA test results will help determine the next step in the DEC’s investigation, the state agency said in a statement.

With the source of the contamination still unknown, the county legislature last month approved spending $200,000 to study the feasibility of installing a treatment system that would kill or filter out the bacteria before it reaches the Sound.

“We’re going to evaluate all kinds of remedies because obviously the [DEC] study didn’t really provide the smoking gun that we were looking for as far as the source of the contamination,” said Brian Schneider, deputy county executive for parks and public works. “We’re shifting focus more toward the treatment at the endpoint of the drainage system, before it hits the beach.”

Schneider said one option to be examined is a filter that “shreds the bacteria” as water passes through it. A similar filter has reduced bacteria counts at the county’s water-pollution control plant in Wantagh, but it’s unclear how effective it would be at Crescent Beach, he said.

Other possible treatment methods the county will look at include using ultraviolet light to kill bacteria and creating a retention pond in which bacteria can die off before water is released into the Sound.