Ten years after remediation was complete at the E.I. DuPont Superfund site in Newport, Del., the area had few options for reuse.
An 18-inch layer of soil capped a landfill where the toxic byproducts of pigment manufacturing had been dumped for decades. A barrier planted between the landfill and a nearby stream prevented the chemicals from migrating. The contamination no longer posed a threat to the environment or workers at nearby factories. But the land wasn’t being used.
The cap was protective only so long as nothing penetrated it, making building anything on the site virtually impossible.
"Redevelopment was a big issue for this site because you cannot dig," said Dina Toto, remediation director for DuPont. "It was just sitting there."
But in 2011, Tangent Energy Solutions approached DuPont with a novel idea to turn the barren land productive: solar panels.
Today, the 0.5-megawatt solar array at DuPont Newport has been online for almost a year, generating more than 1,000 megawatt-hours of electricity.
Building clean energy on contaminated ground is a growing trend for Superfund sites, brownfields and landfills, thanks in part to an initiative launched by U.S. EPA in 2008.
The RE-Powering America’s Land Initiative encourages renewable energy development on contaminated sites by providing technical assistance to developers and educating them about available liability protection.
Renewable energy is being produced at more than 128 contaminated sites across the country with a cumulative installed capacity of 773 megawatts, according to EPA. Solar photovoltaic arrays have been installed on 110 sites, with wind turbines located at 21 others. Geothermal, hydropower and biomass projects have been developed on other contaminated areas. In some instances, the renewables are used to power ongoing remediation efforts.
EPA Superfund cleanups do not always remove all the toxins that contaminate the sites. When concentrations of harmful chemicals are left behind, EPA takes steps to contain them and limit human contact. The practice can also restrict how a site is used in the future, as it did for DuPont.
Locating clean energy generation on contaminated land is a poetic and productive use of space, EPA spokeswoman Liz Purchia said in a statement. The approach, she said, "simultaneously creates a new market for these often overlooked properties while providing a sustainable land development strategy for renewables."
Of course, siting renewable projects on a Superfund site or landfill is not always easy. DuPont developer Tangent Energy Solutions had to engineer a solar array that would be physically stable without puncturing the landfill’s soil cap. Instead of being held down by piles driven into the ground, the DuPont array is weighted with concrete blocks that form a ballast system. The panels sit low to the ground at a gradual angle so they do not catch the wind.
Securing financing for the project was also a challenge because the site’s history scared away some investors who worried about the liabilities of financing a project on contaminated soil, said Tangent’s Vice President of Sales Andy Meserve.
"A lot of investors perceived a liability that was not there" in financing a project on a Superfund site, Meserve said. "We needed to find someone who understood it and who thought of the site as an opportunity and not a risk."
Under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), which established the Superfund program, owners of contaminated land or those who operate it could potentially be held liable for the pollution even if they did not contribute to it. Technically, EPA is not allowed to guarantee it won’t take action against owners or operators of contaminated land, but the agency’s RE-Powering America Initiative does afford some liability protection.
Tenants of contaminated land, including those that lease the land for renewable energy projects, can earn a protected "bona fide prospective purchaser" status from EPA recognizing that the companies did not contribute to the pollution and are not connected to anyone who did contribute to it. The status also recognizes that tenants have cooperated with EPA.
EPA also sends "comfort letters" detailing the history and status of a site to interested alternative energy developers and investors who request information.
For Tangent, EPA’s support was crucial to developing the DuPont solar array. Meserve said that his company has developed projects on brownfields and other contaminated spots in the past but that working on the DuPont project was more convenient because of the amount of data EPA already had about the Superfund site.
"So much work has been done around the site that the conditions are already known," he said. "It makes it easier because there are no surprises."
Part of the contract with DuPont, Tangent and investor Greenwood Energy outlined that DuPont still held all responsibility for maintaining the site’s protectiveness. Tangent would be liable only if work directly related to the solar panels damaged the cap in some way.
Dennis Loria, senior vice president at Greenwood, said the issue of liability, as well as technical issues about how to build an array on the landfill, initially "gave me pause."
"We hadn’t invested in projects like this as a company," he said. "A Superfund site wouldn’t be your first choice of investment because of the liability involved."
But Loria said that when Tangent approached him about the DuPont site, he had recently finished helping his hometown of Acton, Mass., install solar panels on its landfill, something he did as a private resident in his free time. That project made Loria reconsider his professional prejudice against investing in projects on contaminated land, he said. Ultimately, Greenwood decided the array would be a profitable and socially responsible project.
"When you think of what’s the greatest and best use of sites like these, the choice is really having it sit there or making it productive with solar panels," Loria said.
Loria would not divulge financial information about the project but said the DuPont array is "performing well," and Greenwood is now looking to pursue other similar projects.
EPA is not alone in promoting renewable development on contaminated land. In Massachusetts, for example, projects built on brownfields and landfills are prioritized by the state’s solar renewable energy credits program, which requires utilities to buy electricity from solar installations. Michigan offers tax incentives for developers that build renewable energy projects on brownfields.
And renewables have been used not only as a productive reuse of contaminated land but also as a power source for cleanups. At the Re-Solve Superfund site in Dartmouth, Mass., solar panels have been powering a groundwater treatment system since 2012.
There, soil remediation efforts have cleaned the land portion of the site and left it without restrictions for reuse. But a groundwater treatment system must remain in place indefinitely to prevent the spread of dense nonaqueous phase liquids.
A solar array to power the treatment system proved just the fix to cut costs, said Michael Worthy, who works for cleanup coordinator Tetra Tech Inc. The array at the Re-Solve site generates 10 percent more electricity than the pump needs to operate. That means instead of seeing a $35,000 annual electricity bill, the site operator gets a $2,000 credit from the local utility.
"We were thinking of a lot of ways to minimize our environmental footprint, and solar proved to be a very significant way to do so," Worthy said. "It helps us and the environment to boot."