SALEM — The National Grid underground electric transmission cables that run down Derby Street have been leaking oil into the South River basin for years, according to the state Department of Environmental Protection.
Although the last reported leak was four years ago, there were multiple reports in prior years, according to DEP spokesman Edward Coletta.
“One (of our workers) remembers a report of 10 leaks over one summertime,” said Coletta. “(But) we have not had a report of any kind of leak coming from that line since December 2009.”
Others, however, say the leaks persist.
“I’ve called and reported the oil spills and it’s been implied to me from DEP that they know what it is,” said Barbara Warren, executive director of Salem Sound Coastwatch, an environmental organization that monitors coastal waters.
The DEP has told her the oil is not hazardous, Warren said, but when she asked if they wanted a sample from the South River, Warren said she was told, “Don’t touch it.”
“What kind of message are you giving to the public when you say that?” she said. “I think it needs to be clarified. Is it hazardous or is it not hazardous?”
The dielectric, or mineral, oil is used as insulation in the underground, high-voltage transmission lines, replacing a more hazardous oil used years ago that contained cancer-causing PCBs, according to Coletta.
Although the oil is listed in the Massachusetts Contingency Plan as a substance that must be addressed if spilled in large quantities, Coletta said the mineral oil is “probably among the more benign oils we deal with.”
“It’s something you don’t want to have in the environment in large amounts, but it’s more benign than other oils,” he said.
He said vegetable oil is also on the state’s Contingency Plan list.