PLYMOUTH — Extending the deadline for tolling agreements one week will benefit the Environmental Protection Agency and the “potentially responsible parties” in connection with the Howe’s Corner Superfund site in Plymouth, according to spokesmen for both sides.

The EPA is trying to recoup $6 million for the cost of cleaning up an abandoned waste oil site and installing a municipal water system for neighbors of the site who have contaminated wells. If the majority of PRPs sign the tolling agreements, the statutory limit on recovering the costs can be extended two years.

The deadline for signing the agreements came and went last week as the EPA waited for the PRPs to collect more of the agreements. Without the agreements, EPA would be forced to file suits to meet the three-year statutory limit for recovering costs for the 1995 cleanup. Avoiding litigation benefits everyone involved, said the two spokesmen.

The tolling agreements are taken as evidence the PRPs are willing to negotiate to settle the matter, said Erin Heskett, EPA community involvement coordinator.

On Monday, PRP attorney David Littell said: “It’s a benefit to have everyone to sign on with the group, and we’ve got some momentum. It’s clear we’re going to have a settlement.

“It’s better to have everyone signed on so we can have a global settlement and not have those who didn’t sign on hold up the process,” he said.

Earlier this year, the federal EPA identified more than 400 different entities, including towns and businesses, as contributors to the Howe’s Corner waste site once operated by Portland and Bangor Waste Oil. The business collected waste oil for salvage and disposal. The site eventually was abandoned and forgotten until 1987, when contamination was detected in residential well water in the area.

The company’s customers were unaware of how or where the waste was disposed until the contamination was discovered. With the company out of business, the customers will bear the cost of cleanup and eventual remediation of the site.

The PRPs have been organizing since this spring in an effort to coordinate the settlement and reduce the burden on individual parties. The grace period, until this Friday, will allow more PRPs to join the effort.

Earlier this summer, the united PRPs numbered more than 100, with more individuals, businesses and communities expected to sign on. This week, the group is not disclosing how many have joined the effort, because negotiations are ongoing.

The EPA, working with the Department of Justice, is preparing data packages to distribute to the customers who responded to the initial charges. The packages will disclose the available records from the waste oil company and allow individual parties to dispute or confirm information from their own records.

“It’s been so long. A lot of people don’t have those records,” Littell said.

The additional two years for negotiations also will allow the PRPs to develop a “remedial investigation and feasibility study” for final cleanup and restoration of the site. Often the PRPs can conduct a study of this type more efficiently and economically than the EPA, Littell explained. The national average for a remediation project is about $1.6 million, he said.

“Our intent is to develop a limited scope RIFS,” he said, explaining the study should meet the needs of the EPA and the PRPs and save money for everyone involved.

The PRPs already are picking up the cost of quarterly water monitoring for wells outside the municipal system, but within the potential for contamination, according to Heskett.