NORTH PROVIDENCE, R.I. — One of the most toxic Superfund sites in New England is preparing to undergo a substantial and costly cleanup.

If approved, an estimated $100 million will be spent on a fifth and final scrubbing of 9 acres of developed land and surrounding watershed saturated with dioxins, pesticides, and PCBs. Two contaminated ponds would also be temporarily drained as part of the planned cleanup.

Much of the most toxic land is covered by a parking lot and two apartment buildings. The Superfund site also sits upstream from ecologically sensitive and highly polluted ponds and wetlands.

The Environmental Protection Agency (EPA) has proposed draining the Allendale and Lyman Mill ponds to excavate 156,000 cubic tons of contaminated sediment. Polluted soil and water will be contained on site, treated, or shipped out for disposal.

The last of three public information meetings hosted by the EPA was held Nov. 10 at the Centredale Manor Retirement Home, one of the structures built over this Superfund site.

“We’re at the point to address long-term cleanup of the site,” EPA community liaison Stacy Greendlinger told an audience of about 30 Centredale Manor residents.

Due to extensive regulatory and approval requirements, the cleanup isn’t expected to start for about five years, she said. When completed by 2020, the EPA intends to classify the Allendale and Lyman Mill ponds as swimmable and fishable. Both ponds are fed by the Woonasquatucket River.

Most of the 184,000 cubic yards of contaminated material comprising the top 4 feet of soil will be removed and disposed of in Rhode Island and out of state, according to the EPA.

Three feet of clean fill, capped with a layer of plastic, will replace the soil. Some of the capped land will be usable as open space for athletic fields and other uses.

The cost of the project is expected to be covered by the polluters.

Between 1943 and the 1970s, the chemical manufacturing company Metro-Atlantic and the incinerator-based drum recycler New England Container released toxins and dumped chemicals directly into the ground and river. Harmful waste also was buried onsite. Pollution from the facilities has contaminated surface water, the water table, watershed area and downstream water that flows to Providence. Fish and birds also contain unsafe levels of contaminants.

A fire in 1972 destroyed most of the buildings, Brook Village Apartments was built in 1977, followed by Centredale Manor in 1982.

It wasn’t until 1996 that the EPA began to study the extent of the contamination. In 1998, the first small-scale cleanup took place to reduce the immediate health threat to residents. Two other cleanups occurred in 2000 and 2003. In 2000, the site was added to the federal Superfund list.

Public comment on the latest project ends Jan. 12. Two public hearings are scheduled for Dec. 7 at 2 p.m. at Centredale Manor and 7 p.m. at Town Hall.

“That must be cleaned so that hopefully things will be cleaned up as they were before,” said Mike Jasinski, sector chief for Superfund sites in Rhode Island and New Hampshire.