Terry Connelly remembers clipping out a 2002 newspaper headline declaring an end to the long-running saga of the McKin toxic waste site in Gray.

It was a satisfying, mission-accomplished moment for Connelly, who lives in Eliot and oversaw the site for the U.S. Environmental Protection Agency. The sad stories of all the people affected by poisoned groundwater around the former dump are still with him.

But toxic waste sites have a way of hanging around and causing headaches, or worse, long after the cleanup crews pull out. “They don’t seem to go away,” Connelly said.

Connelly is part of an EPA team revisiting the McKin neighborhood this summer as part of a five-year review. He hopes to find that nature’s self-cleaning cycle is making progress. But it’s a forgone conclusion that the plume of toxic chemicals is still lingering deep in the sand, gravel and bedrock, moving very slowly into the Royal River.

And there is an emerging concern that the chemicals left behind could still pose a health threat in the form of vapors seeping up through the ground.

The McKin Co. began dumping oil sludge and industrial solvents into a former gravel pit off Mayall Road in the 1960s. The waste came from more than 400 businesses, school districts, municipalities and churches.

In 1975, two friends living near the site noticed stinky drinking water. After one had a miscarriage, they began hearing about a range of health problems in the neighborhood, including skin rashes.

Tests finally identified industrial contaminants in the water two years later, and the town shut down McKin and began extending public water to the owners of 50 contaminated wells.

McKin became the catalyst for a whole set of state laws regulating the hazardous waste sites that would follow. It emerged around the same time as other toxic sites around the country, including one in a New York neighborhood called Love Canal, and eventually became one of the first in Maine to be named a federal Superfund cleanup site.

The parties that sent waste to McKin spent more than $21 million on the cleanup, which included pumping and treating groundwater for several years. The active cleanup was declared over in the late 1990s after experts decided the site would clean itself naturally within about 50 years, just as fast as the pump-and-treat effort.

The groups that had been financing the cleanup paid a $4.5 million settlement to landowners and other parties. And in 2002 the story was declared over.

Groundwater and the Royal River continued to be monitored, however, and will for decades more. The Royal River has been meeting water quality standards, even at the point where the groundwater plume discharges into it, Connelly said.

But the old dump site may still be capable of harming its neighbors.

When the cleanup was declared over, no one thought of toxic vapors seeping up through the soil into homes and buildings.

“It wasn’t on anyone’s radar screen,” Connelly said. “And then a couple years later, we start hearing these stories about other sites … We’re seeing it throughout the country.”

EPA officials plan to test air quality in some Gray homes this summer, he said. If there is any evidence of “vapor intrusion,” the contaminants would be vented away much like radon gas that seeps into basements.

It’s another reminder, Connelly said, that avoiding a mess is a whole lot cheaper and faster than cleaning one up.

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