Swisshelm Park slag heap nearly cleaned up, ready for solar makeover

An old slag heap leftover from a former steel manufacturing waste dump is more than halfway done getting cleaned up, in order to transition into a 15-acre sea of solar panels. The Urban Development Authority, which owns the property, held a meeting Thursday to give community members an update on their progress.

“ I think it’s a really exciting example of a revitalization story,” said Lilly Freedman, senior manager of development projects at the URA. “With our history of deep industry, of steel manufacturing and the waste product that has really visibly scarred the landscape of our city for years, this is a story of actually remediating into something new. It’s a kind of beautiful change into a greener future for the city of Pittsburgh.”

Before getting underway with its plans for solar, the URA had to remediate the 70-acre site before doing anything with it. To do so, contractors are keeping the slag in place and capping the site — to avoid releasing toxic dust into the air that might come with removing the slag.

They’re at work putting in a mix of clean soil and topsoil about a foot deep across the site. Then they’ll start planting trees, such as Boxelder Maple, Honey Locust and American Sycamore, and a “meadow mix” in other spots to hold it in place and keep the toxic slag underground. They’re on track to finish the remediation by the end of the fall, depending on weather.

After they’re done with the $3 million remediation, the URA will hand over 55 acres to Frick Park’s bounds — making legal some informal trails blazed through the site.

“The folks we work with in the community are just thrilled about being able to expand Frick Park and really clean up this site and be able to give it back to the public in a way that is fully legal, fully safe from a public health perspective,” Freedman said. “It’s an opportunity to expand one of Pittsburgh’s biggest assets in our largest public park.”

The URA plans to put out a request to find someone to develop the south-facing, flat, exposed 15 acres for the solar field at the end of the year, beginning of 2026. If all goes to plan, a field of solar panels would be soaking in sunshine in early 2027.

Pittsburgh isn’t known for its warm rays, but is similar to cities such as Boston and Philadelphia, in terms of its global horizontal irradiance — the best indicator of a location’s solar potential. And unlike wind turbines that need a threshold of wind speed to get the turbines running, there is no minimum amount of sunlight needed to generate electricity.

Solar is cheap, thanks in part to tax credits and lower technology and installation costs. It has the lowest levelized cost of energy in most places, according to a 2024 report from Berkeley Lab.

The solar array in Swisshelm Park is expected to produce about three megawatts of electricity each year — approximately what’s needed to power 175 homes each year.

But the solar produced from the site won’t likely be used to power nearby homes. The URA won’t be selling the energy to anyone. Instead, they will likely lease the land to a solar developer who will sell the power to a big energy user located within a two-mile radius of the site — like a school, hospital or other large institution, according to Freedman.

For now, an end to the truck traffic from construction is in sight and with it a transformed piece of land. “The public health benefits are something that really thrill me about this project,” Freedman said. “Even this remediation phase is a huge win from my perspective — what it means to clean up a 70-acre site in our city.”