PLYMOUTH – The Environmental Protection Agency has exempted 40 Maine businesses and municipalities from the multimillion-dollar hazardous waste cleanup at the Hows Corner Superfund site.

Entities that contributed less than 110 gallons of waste oil to the site qualified as “de micromis” parties under the Small Business Liability Relief and Brownfields Revitalization Act passed by Congress last year.

Once categorized as “potentially responsible parties,” or PRPs, by the EPA, the 40 different groups received letters last week saying they had been exempted from liability for groundwater cleanup of the site.

The remaining 100 PRPs eventually will be assigned to cover portions of the estimated $8 million cost by EPA officials.

The Hows Corner site is the only one of 13 active Superfund sites in the state that now appears to be affected by the exemptions, according to Mary Jane O’Donnell, EPA section chief for Vermont, Maine and Connecticut.

The 17-acre site includes a 2-acre area where landowner George West Jr. of Wells operated a waste oil storage and treatment facility from 1965 to 1980. In affiliation with Portland-Bangor Waste Oil Co., West collected and stored mostly waste oil from auto dealerships, utility companies, bulk transportation companies and municipalities.

After routine testing of a homeowner’s well in 1987, the Department of Environmental Protection identified the site as a source of polychlorinated biphenyl that contaminated more than a dozen wells in the area.

In 1998, more than 300 PRPs were connected to the site, although the number later narrowed to approximately 250, according to Bill Lovely, project manager for Hows Corner. Over the past couple of years, some smaller PRPs entered into cash settlements with larger groups because of a documented inability to pay, Lovely said.

Those parties exempted from further liability include the municipalities of Belfast, Calais, Greenville, Orono, Searsport; SAD 1 (Presque Isle area); SAD 27 (Fort Kent area); SAD 34 (Belfast area); and several private businesses and organizations.

After town revenue records turned up no proof that Orono used the waste oil facility, the town spent close to $15,000 in legal fees debating its liability for the site’s cleanup, according to Town Manager Gerry Kempen. While the legal debate never lifted the town’s liability, the recent exemption will mean a significant saving for Orono.

“This exemption relieves us of a potentially huge financial burden in the future,” Kempen said. “It’s unfortunate that we had to pay as much as we had up until now.”

In the near future, the EPA will move ahead with negotiations with the remaining 100 PRPs to fund the remaining stages of cleanup, Lovely said.

Interim plans were adopted last year to install an extraction and treatment system to prevent further migration of the contaminants from the source, Lovely said. Although the EPA installed a public water system in the 1990s for homeowners whose wells might be contaminated, officials also will continue to monitor private wells.

“No one’s drinking contaminated water right now,” Lovely said.

The EPA and the Maine Department of Environmental Protection already have spent close to $6 million on removing 847 tons of contaminated soil and installing a water system to serve 36 homes in the area.

At this point, the timeline for the remaining cleanup is uncertain, Lovely said. Officials will rely on Mother Nature to absorb smaller amounts of contamination outside the 2-acre containment zone, he said.

“It could be anywhere from several decades to several hundred years,” Lovely said.