CRANSTON, R.I. — Last month Gov. Dan McKee with other state and local leaders cut the ribbon on the Beacon Solar Project. Nestled between Pontiac Avenue and the Pawtuxet River, the development hosts 9,000 ground-mounted solar panels that can power 509 households. Subscribers to the community solar project are expected to save about 10 percent on their electric bills.

The 3.5-megawatt project is a joint venture between East Providence-based ISM Solar and Nautilus Solar Energy LLC of New Jersey.

The site represents a win for homeowners and solar developers alike. Solar construction is controversial, as residents complain of installations being humming eyesores and environmentalists note the destruction of open space and forestland to site them. But the Pontiac Avenue array sits on top of a former Environmental Protection Agency Superfund site that is otherwise largely undevelopable, the Cranston landfill.

“There’s more environmental due diligence on this project, making sure the site had been properly closed, that it met all the requirements,” said Eric LaMora, director of community solar for Nautilus. “We had to do a lot of diligence on our site to make sure the environmental aspect of the site is maintained.”

In operation between 1942 and 1985, the landfill accepted solid municipal waste from across New England. But it had a host of environmental problems. The landfill was a source of leachate seepage and was responsible for contaminating groundwater. In 1988, it was discovered that the landfill’s operator had been unlawfully accepting hazardous waste, prompting the first cover laid over the site.

State officials performed a remedial investigation from 1999 to 2003, evaluating the extent of the contamination and future risk. Final site remedial objectives were issued by the Rhode Island Department of Environmental Management (DEM) in 2008, dictating a final cover system be put in place, new gas wells be installed on the site’s north side, and extensive groundwater and surface water monitoring be conducted.

National Grid, Chevron, General Dynamics, Pfizer, and Textron were among the 43 entities found to have contributed hazardous waste to the site. The companies settled out of court, contributing money to a multimillion-dollar fund to remediate the site.

The Beacon Solar Project is not the first partnered development between ISM Solar and Nautilus. A few years ago the companies worked together to develop a ground-mounted solar array in Burrillville.

ISM Solar acts as a local liaison throughout the region. It negotiated with the Capuano family who owned the land Beacon sits on and secured all the necessary permits from the city and DEM — the latter “a pretty significant lift,” according to LaMora. Nautilus credited the usage of ClosureTurf, a patented three-layer cap cover, for easing construction on top of the landfill.

ISM Solar is well known around the state, sometimes controversially, for aggressively building solar projects in residential areas. Nautilus, the long-term operator of the site, runs dozens of existing solar arrays nationwide. It is the company’s first brownfield/Superfund site in Rhode Island, but not nationwide. It operates a solar array on top of a landfill in Maryland and at a handful of gravel pits in Maine.

Avoiding cap disturbance is key when developing on contaminated sites. Normal ground-mounted solar arrays are secured in place by penetrating the entire system into the ground. On the Beacon project grounds and other capped sites, the solar panels instead sit directly on top, weighted down by some 60,000 ballast blocks to counteract wind lift.

Building on a brownfield/Superfund site also requires extra engineering, extending a project’s completion time by some six months. The panels installed at Beacon are fixed tilts, the site’s cap would be too sensitive to moving panels. Developers estimate an 80 percent loss in kilowatt-hours from fixed panels, and that impacts project revenue.

While solar developers would appreciate financial incentives from the government to build on contaminated sites — to help offset remediation work and longer project times — the real hurdle to developing on a brownfield/Superfund site is indemnification. Underwriters are cautious about insuring sites with a complicated legal history and an environmentally unsure future. Nautilus has a strong sponsor and large balance sheet, but smaller developers can have a harder time getting financial backing for similar projects.

“We had to go through a lot of due diligence to make sure [our insurers] were comfortable with that exposure,” said Laura York, Nautilus’ executive director of structuring. “Not every developer can take on that kind of liability.”

A 2020 analysis funded by the state’s Office of Energy Resources showed a severe underuse of solar siting on already-developed sites. The report counted 404,594 solar-possible sites, such as rooftops, parking lots, landfills, brownfields, gravel pits, and other commercial or industrial parcels.

Preliminary data from the analysis showed Rhode Island could increase the megawatts generated by solar to 3,390 — 13 times higher than the 250 megawatts solar panels power now. Estimates in the analysis indicated utilizing solar across the sites would displace 7.65 million metric tons of carbon dioxide, equaling 70 percent of the state’s current greenhouse-gas emissions.

Beacon project developers do not anticipate any future environmental hazards to occur at the site. Much of the site’s engineering was designed to avoid harming the cap in any way, and the site will periodically undergo inspections for any possible disturbances.

During the past several years, a handful of community solar projects have gone online, including a 12.44-megawatt, ground-mounted array built on tree- and brush-covered land in North Smithfield deemed unsuitable for other development.