The towns of Oyster Bay and Hempstead will require advance notice to property owners when monitoring wells or other excavations are dug as the Navy and Northrop Grumman work to find the boundaries of a groundwater plume that has spread more than 4 miles from Bethpage.

The move comes as drilling rigs have been popping up in the area to investigate a hot spot of contamination revealed last year, and as Hempstead has closed two wells in Levittown because of toxins from the plume.

"Information is power," Hempstead Supervisor Kate Murray said. "Everybody is going to be interested in any work going on in this regional area because this all flows from the same problem, the same pollution."

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The Town of Oyster Bay highway department, which issues permits for work on rights of way, has begun requiring drill applicants to meet with property owners in advance of when work will take place and then follow up with a letter detailing the scope.

And later this month, the Hempstead Town Board will hold a public hearing over new legislation ordering agencies doing environmental testing, such as drilling, to give two weeks notice to property owners. The notice will have to include the scope and hours of work, the company performing the work and the duration.

Violations will carry a $250 fine, though the intent is to provide better information to residents. "We think that is the absolute minimum that should be accorded in the category of courtesy," Murray said.

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The Navy and what is now Northrop Grumman manufactured aviation equipment and other aeronautical advances on more than 600 acres in Bethpage beginning in 1936. Production ended in the late 1990s.

Contamination was first discovered in 1947 and the sites were added to the state Superfund program in 1983 by the Department of Environmental Conservation.

Two plumes are being treated and a third "hot spot" is now being investigated after the Navy last year detected levels of the degreaser trichloroethylene at up to 4,600 parts per billion. The drinking water standard is 5 parts per billion.

As part of the "hot spot" probe, the Navy is installing 31 monitoring wells north of Hempstead Turnpike and north and south of the Southern State Parkway.

Northrop Grumman would not provide the number of wells it intends to drill and a spokeswoman referred questions to the Navy.

"Together with other responsible parties, we are collectively performing all state-required work . . . ," Grumman spokeswoman Christine M. Restani said in a statement. "We continue to work closely with the state, including discussing a mutually acceptable order to address ongoing remediation."

John Ellsworth, an environmental consultant for Oyster Bay, said Northrop Grumman has about a half-dozen drills in place and is seeking permission for more. The town has asked for, but has not yet received, a schedule and list of drill sites related to the hot-spot probe.

"They're filing applications one after another," Ellsworth said. "They may have to drill new wells to catch where this hot spot is."

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Under state environmental law, property owners must be notified "in advance of drilling or sampling that will occur on their property," the DEC said in a statement. "This does not include rights of way."

The Navy and Northrop Grumman have said they will send notification by certified mail to nearby addresses, the DEC said.

The Bethpage Water District has also asked the DEC to require three weeks notice to the district before drills appear and to provide information about who is doing the work.

"I think we have a right to know who is working in our community," Bethpage Water Superintendent Mike Boufis said. The DEC said the request is under review.