NORTH MANKATO — North Mankato has a gas problem.

The city's Public Works Department, 610 Webster Ave., has methane gas trapped underneath its facilities according to recent tests conducted by contractors and the Minnesota Pollution Control Agency.

North Mankato's Public Works building was built over a former landfill that closed in the 1960s. While the city has had a soil and gas plan for the facility for some time — daily gas tests have been conducted since 1992 —a recent test conducted with MPCA officials found evidence of higher than normal methane readings underneath the building.

"All the gases have built up from the past refuse that people have dumped in there, and we just need to release the gas, in essence," Public Works Director Brad Swanson told the North Mankato City Council at a public meeting earlier this month.

Swanson this week said one of the holes drilled underneath the building as part of the test showed air that was 70 percent methane.

The city conducted further tests in mid-November to determine just how much methane is held below the Public Works building. The MPCA is preparing a final report for the city, which North Mankato officials will use to figure out how much it will cost to siphon the methane out of the property.

City officials estimate it could cost $100,000 to $200,000 to get rid of all the gas, and Swanson said it's still too early in the process to tell how expensive the project will be. The property will likely require at least five permanent vents in the future to prevent further gas buildup.

It's also too early to tell whether North Mankato can trap any of the methane to be resold, but city officials are looking into the process.

"We're just going to hope for the best, that it's a rather inexpensive repair, so we'll just hope for the best as we move forward," Swanson said.

Removing the methane will likely be added to the city's infrastructure projects list once the MPCA's report comes in. City Administrator John Harrenstein told the council earlier this month the added cost, combined with previous talks about the state of the nearby Street Department building, could provide a catalyst to start talks on building future facilities depending on how expensive those projects become.

"It does need to start to become on our radar," Harrenstein said. "If we're going to be doing large-scale mitigation, we need to be looking at the future as well."

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