Activists Dawn Chapman, left, and Karen Nickel wear protective masks at the West Lake Landfill in Bridgeton, Mo., north of St. Louis. The site, part of which is listed as among the nation's most toxic messes, includes radioactive waste illegally dumped in the 1970s. (Linda Davidson/The Washington Post)

The Environmental Protection Agency on Thursday ordered an aggressive cleanup of a long-controversial landfill contaminated with radioactive waste near St. Louis, delighting community activists who have fought for such an outcome but angering companies who argue that the agency’s own science called for a more modest cleanup.

“This action reflects President Trump’s commitment to return EPA to its core responsibility — clean air, clean water and clean land,” EPA Acting Administrator Andrew Wheeler said at a morning news conference of the West Lake Landfill in Bridgeton, Mo., which has lingered on the agency’s Superfund list since 1990. “We believe this decision strikes the right balance, while emphasizing the health and safety of the community.”

Wheeler’s decision is the latest signal that he intends to largely follow the policy course set out by his predecessor, Scott Pruitt, who resigned from EPA in July amid a flurry of federal ethics investigations. Pruitt was eager during his tenure to balance his industry-friendly regulatory rollbacks with a commitment to accelerating cleanups at the nation’s Superfund sites, saying such work was more central to the agency’s mission than combating climate change and helping shift the nation to cleaner sources of energy.

Wheeler, who has continued to dismantle Obama-era policies, said Thursday that his decision on West Lake “reflects our larger commitment to the nation to expedite the remediation of Superfund sites across the country.” The EPA’s order, which caps decades of bureaucratic delay, intense debates and public protests, is expected to take fewer than five years and cost those responsible for the site an estimated $205 million.

The West Lake Landfill contains thousands of tons of radioactive material from the World War II-era Manhattan Project that was dumped at the site in the 1970s, where it has languished ever since amid other waste. The latest plan calls for excavating 70 percent of the radioactive waste from the site — a far cry from a 2008 solution proposed by the George W. Bush administration to cover and monitor the waste.

Thursday’s final decision triggered a wave of texts and tearful phone calls among a collection of community members who had been fretting about the radioactive material near their neighborhoods and lobbied for the government to finally remove it.

“This administration listened to us. I don’t know how else to put it,” said Dawn Chapman, a founder of Just Moms STL, an activist group that has pushed for an extensive excavation of the site and possible relocation of families near the landfill. “For the first time, we’re going to have our community put back together. . . . I’m angry it took so long, but I’m relieved.

Thursday’s decision hardly brought such relief to Republic Services and Exelon, whose subsidiaries are responsible for the cleanup at West Lake, along with the Energy Department. In a statement, the subsidiary of Republic that oversees the site called the order “arbitrary and capricious.”

The firm is “opposed to the selected excavation because it creates unacceptable risk with no proportional benefit, will greatly increase the time needed to remediate the site, and is contrary to EPA’s own findings regarding the risks posed by the site,” the firm said in a statement. It added that the 2008 recommendation to “cap and monitor” the waste wouldn’t have risked exposing workers and community members to waste as it is excavated and moved elsewhere.

The Trump administration rejected those arguments. Pruitt’s order from February would have forced the companies to undertake a $236 million cleanup that would dig down roughly 16 feet into the landfill to remove as much radioactive material as possible.

By contrast, Wheeler’s final plan will allow workers to dig between 8 and 20 feet below the surface of the landfill, in an effort to focus on areas where radioactive waste is most concentrated. Wheeler said the cleanup is expected to happen a year faster and cost $30 million less than Pruitt’s plan. The agency estimated that about 75,000 cubic tons of contaminated material would be taken off-site by rail and truck.

Before he resigned, Pruitt had promised to speed up Superfund cleanups around the country, and he made a public show of butting heads with corporate interests — something he otherwise rarely did during his time at the EPA.

Not long after Hurricane Harvey battered Houston last summer, Pruitt ordered two corporations responsible for a toxic waste site that flooded near the San Jacinto River in Texas to spend $115 million to excavate the contamination rather than leaving it covered. His dramatic decision put Pruitt in unfamiliar territory: Environmental activists cheered, while the targeted firms protested that the directive was not backed by science and could expose more people to health risks.

Still, aside from creating a list of nearly two dozen target sites that needed “immediate and intense” attention, as well as forming a task force to recommend ways to expedite cleanups and “reduce the burden” on companies involved, Pruitt never explained precisely how he intended to deal with the hundreds of other toxic-waste sites that remain around the country, waiting for attention.