Fifteen years after the former Grumman defense plant in Calverton shut down, investigators have traced an underground plume of chemicals that threatens the nearby Peconic River back to a spot on the property where jet aircraft systems were once tested.
The Navy, which once owned the Grumman property and still controls the smaller parcel where the plume is thought to have originated, released the results last month at a meeting with a local citizens advisory board. Contaminated soil was removed from the area early this year. Now the Navy is evaluating the best way to clean up the groundwater and expects to release a draft plan in March.
"The source is cleaned up, so it's not polluting it any more," Navy spokesman Thomas Kreidel said Monday. "Now it's a matter of: We've got this plume, now what do we do about it?"
The Navy had earlier said the contamination - a mixture of chlorinated solvents and jet fuel - was diffuse and would most likely dissipate on its own. The Navy reversed course this spring after tests initiated by the Suffolk County Health Department revealed the chemical plume was more concentrated and widespread than originally estimated.
"I think they've seen the light," said William Gunther of the citizens board.
Cleanup options include pumping up the polluted groundwater. The Navy is also looking at injecting groundwater with a corn-based compound to speed breakdown of contaminants.
Groundwater tests conducted this fall offer the most precise picture yet of the plume's size. It stretches more than a mile between the Grumman parcel on River Road and the Peconic River. From 100 to 200 feet wide near the source, it broadens to 2,000 feet as it moves southeast.
Hydrogeologists believe the plume comes from chemicals spilled when jet engine and fuel systems were tested between the 1950s and 1980s. In some spots, concentrations of Dichloroethane - an industrial degreaser - are up to 200 times higher than the state drinking water standard.
"It was surprising to see levels this high that many years from the discharge," said Andrew Rapiejko, an associate hydrogeologist with the health department's division of environmental quality.
The plume does not threaten public drinking water supplies beyond a well at the Peconic Sportman's Club, which has been fitted with a filter to remove contaminants.
But residents, local officials and environmental advocates worry that the pollution will harm water quality and aquatic life in the Peconic River.
Suffolk Legis. Edward Romaine (R-Center Moriches) said the Navy must act. "We've let too much time go by," he said. "The Navy has an obligation to come back and clean up the mess they made."