At three large tracts in the Wood-Pawcatuck Watershed, remnants of an industrial past have yielded cornerstones of a conservation-minded present and future.

The Francis C. Carter Preserve in Charlestown was once the home of United Nuclear, a nuclear fuel recovery plant for two decades that was infamous for the radiation exposure death of one of its workers in the mid-1960s.

After the company closed in the early 1980s, the federal government designated its property a Superfund site and a 30-year cleanup began.

Today, the 1,100-acre parcel of pitch pine and hardwood forest on the Pawcatuck River is the second largest Nature Conservancy property in Rhode Island.

The largest is the 2,054-acre Tillinghast Pond Management Area in West Greenwich, at the northern end of the Wood-Pawcatuck Watershed.

“Through the 1970s, wastewater from the plant went directly into the river. After that it went into onsite lagoons to drain through the sandy soils,” said Tim Mooney, manager of the Carter preserve.

After the first phase of cleanup was done in 2001, the conservancy obtained the first 830 acres from General Electric, which had bought out United Nuclear.

In December, after contaminants were removed from the remaining 270 acres, the conservancy obtained a second key piece with a mile of riverfront.

“We’ve been chasing the rest of this property for 13 years,” Mooney said, bushwhacking through forest to reach the riverbanks one day last month, ahead of planned trail construction this summer.

When United Nuclear owned the property, he said, it only used about 10 to 11 acres of the entire parcel for its operations, so most of the property has been undisturbed for generations.

The acquisition, he said, was part of the conservancy’s conservation strategy for New England, decided upon 10 to 15 years ago, to focus its land conservation projects on areas with large, healthy forest blocks and healthy river systems.

In the Wood-Pawcatuck Watershed, the large amount of protected land and the state of the waterways earned a place on the nonprofit group’s priority list.

“The Pawcatuck and several of its tributaries met the criteria for water quality and biodiversity,” Mooney said.

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About eight miles west, in Hopkinton and Westerly, the adjoining Grills Wildlife Sanctuary and Grills Preserve cover about 1,150 acres of land formerly part of a textile company, the Bradford Dyeing Association, once owned by the Grills family.

Trails through the preserves pass remnants of a dam and sluiceway from another mill that once stood on this part of the Pawcatuck River.

“We are really grateful to the Grills family for making it possible for us to purchase this property,” said Kelly Presley, executive director of the Westerly Land Trust, owner of the Grills Preserve. “They could have sold it to a developer.”

BDA discharged its wastewater directly into this section of the river through the 1970s, when the federal Clean Water Act prohibited the practice. After that, the company used open lagoons to treat its wastewater.

Christine Anderson, president of the Friends of Hopkinton Land Trust — owner of the Grills Wildlife Sanctuary — is a lifelong resident of the area. Over the years, she’s noticed a shift in attitudes about the region’s natural resources.

“Growing up, my family really weren’t nature people,” she said, as she and Presley and Marci Redinger, secretary of the Friends of Hopkinton Land Trust, hiked past a meandering, swamp-like stretch of the river called an oxbow. “But now there’s definitely more of an interest in in the river, and it seems everyone’s more supportive of preservation.”

j.benson@theday.com

Twitter: @BensonJudy