Still, Kimmel said, “we reserve the right to recommend commencement of the Superfund listing process if the issues are not resolved by that time.’’
The sprawling property located off King and Winter streets also borders Hanson and Pembroke. One of its early inhabitants was an 18th-century forge that made cannonballs for Old Ironsides.
Over the years, the property also hosted the National Fireworks Co., which made pyrotechnics from firecrackers to cherry bombs, and the Defense Department, which used the site to manufacture munitions and explosives for the military from World War I to the 1970s.
As a result of those uses, pockets of mercury, lead, and other heavy metals and solvents from the manufacturing processes are buried in the sediment of the adjoining Factory Pond and tributaries of the North River.
The state has already completed three phases of cleanups at the site, including removal of human health risks like drums of chemicals left there decades ago by the Massachusetts Institute of Technology.
The state is currently in negotiations with Kerr-McGee Chemical Co., National Coating Inc., MIT, and the Department of Defense, said Donald Nagle, an environmental lawyer hired by the five-member Hanover board to help shepherd the mitigation process.
Tronox, another former owner, settled with the federal government two years ago and then went bankrupt, he said.
Under Phase Four of the cleanup plan, ecological hazards would be excavated from the sediment or capped, officials have said.
It’s the second six-month extension the town has requested and received in a year.
Hanover selectmen have been insistent that they want the state to retain control while also laying the groundwork to get a long-overdue cleanup on its way, Nagle said.
