Another federal deadline has come and gone, and the Minnesota Pollution Control Agency (MPCA) still has not figured out how to clean up one of the state’s largest closed landfills.

Wet weather and drilling problems delayed research and negotiations on the future of Freeway Landfill, which has sat — unused — on the edge of Burnsville near the Minnesota River for decades. The agency was supposed to have a plan for the privately owned landfill by Monday.

Instead, the MPCA and local government officials are waiting to hear if they can have a second extension from the U.S. Environmental Protection Agency (EPA) to come up with an agreement that protects the environment and residents.

Past attempts to improve the hazardous property, owned by the McGowan family, have failed, forcing the EPA to threaten to take over. If that happens, the agency sues polluters to pay for remediation.

“It’s a litigious process,” said Heather Johnston, city manager in Burnsville, where city leaders would like to see mixed-use development on the property. “It impacts a lot of folks, so obviously that would delay any future development there.”

The EPA’s approach doesn’t work well for landfills that were used by thousands of residents and businesses, MPCA Assistant Commissioner Kirk Koudelka said.

That’s why Minnesota in 1994 launched the Closed Landfill Program, which manages more than 100 landfills around the state that are no longer operating.

But Freeway Landfill is particularly complicated.

Burnsville and Savage draw drinking water from a quarry next door. Kraemer Mining & Materials pumps water from the site, keeping the water table low — so low that it doesn’t touch the buried waste.

Officials are studying what would happen once the mining company stops pumping and the water level rises. That’s expected to be in 15 to 20 years.

“When the groundwater starts to go back to its previous state, before Kraemer’s quarry, what would that do for our waste that’s sitting there?” Koudelka said. “Does it move? Does the groundwater cover it and then transport it to the river or to the lake or does it go elsewhere?”

Fixes cost millions

Freeway Landfill holds 5 million cubic yards of trash, enough to have filled the Metrodome more than twice. The waste includes heavy metals, acids, battery casings and more, according to EPA documents.

The water might still meet state health and safety standards if it touches the trash, Koudelka said.

If that’s the case, state and local government officials could pick the cheapest option of leaving the trash where it is and putting a cover over it for $29 million.

But if the water becomes contaminated and violates standards, the MPCA would dig under the waste and put a protective liner below it, which would cost about $62 million, according to state estimates. The most expensive option, at $69.7 million, would move the waste slightly to the west, on top of a protective liner.

For Burnsville, that could leave more room to develop the site, which city leaders call the Minnesota River Quadrant.

“The more developable land available, the better it is for everyone in terms of future tax capacity,” said Johnston, the city manager, adding that the city’s top priority is a solution that protects the environment and residents’ drinking water. It’s up to the MPCA and Minnesota Department of Health to make sure that happens, she said.

The MPCA asked the EPA to give it until Oct. 30 to continue studying health and environmental impacts and to reach an agreement with the McGowans and local partners on the future of the site — and how to pay for cleanup.

Landfill owner Michael McGowan said he understands an extension has been requested, but he declined to comment further.

The federal agency confirmed that it has received the MPCA’s request and that it is working on a response.