MANSFIELD - After decades of inaction, the former Hercules landfill off Stearns Avenue could be capped as early as this fall.

The fear was the landfill, which runs just under two acres and is now owned by the town, had hazardous waste dumped there in the 1950s by the company, which has been paying for most of the studies of the site and would likely pay for the capping.

"There was no oil or hazardous materials," Attorney Mark Roberts, the town's environmental counsel, informed selectmen this week.

"We were fortunate Hercules didn't dump anything nasty. We expected to find a lot of chemicals."

There is, however, about 40 feet of "gooey, blue clay" that Roberts called a smelly mess that would be "horrendous" to move and cost about $1 million to do so. Plans are to scrape off significant concentrations of the waste, which stemmed from the production of pentaerythritol, stockpile it on site and cap the landfill.

An engineering consultant, Weston and Sampson of Peabody, is planning the capping.

Although the state Department of Environmental Protection doesn't presently consider the substance hazardous - it has been used in food products - it has been investigating for 18 months how to classify it, holding up landfill site work, Roberts said. It could be classified as hazardous, he acknowledged.

A consultant firm for the town is doing its own inquiry, even translating from Japanese a study on the substance, Roberts said.

If it is deemed hazardous, further work at the site would likely be needed, Roberts said.

Pentaerythritol had been present, but it had been consumed by insects, Roberts said. "The bugs love it," he said.

Selectman George Dentino supported moving ahead with plans for using the remainder of the 40-acre site, possibly for passive recreation such as athletic fields and a park.

"That is a beautiful piece of property," Dentino said, noting there are nearby ponds. "It is a very worthwhile, valuable site for the community."

Selectwoman Sandra Levine suggested setting up a workshop and inviting pertinent individuals, and that is planned.

The town purchased the land, including the landfill, in 1964. Although the intentions were to use it as a secondary town landfill, town refuse was never disposed of there. The property has been investigated many times dating back to the 1960s, with no significant contamination detected, Roberts said. The DEP in the '80s ordered the town to close the landfill.

STEPHEN PETERSON can be reached at 508-236-0377 or at speterson@thesunchronicle.com.