RAPIDAN — The detection of some volatile organic compounds migrating out of the oldest part of the Ponderosa Landfill is triggering a public meeting to give people information on plans to mitigate the problem.

Officials from Blue Earth County and state pollution officials say no chemicals have been detected in nearby private wells, and they don’t expect the compounds will ever affect private wells.

“We certainly don’t want to minimize the problem, there’s definitely chemicals of concern there,” said Dave Kronlokken, solid waste officer for the county. “But we’re talking about very small quantities, parts per billion. And the water affected is in the uppermost aquifer. Virtually all the residential wells in that area are in a deeper aquifer that isn’t impacted.”

Nancy Miller, an information officer with the Minnesota Pollution Control Agency agreed.

“Honestly, the chance of (well contamination) would be very remote,” she said.

The Ponderosa, southwest of Mankato, and northwest of Rapidan, was opened in 1972 in an abandoned gravel pit. At the time there were few regulations on landfills and no liner was installed under the landfill as is now required.

The original 27-acre site was closed in 1994 and a permanent cover placed on it to prevent rain from soaking into the landfill.

Kronlokken said they suspect that gases created from decomposing garbage in the landfill have been trapped, can’t escape through the top of the landfill cover and are being pushed down into rock and water. There were already passive gas vents in place, but they apparently weren’t enough to release all the gases.

The county has already added an “active gas system” to pull the gases out. Holes are dug and a blower fan sucks the gases up.

“The system extracts the gas so it won’t go anywhere,” Kronlokken said. “But at this point it’s not possible to draw out that gas that’s already traveled down. We can stop it where it’s at, though.”

Monitoring wells around the landfill are tested quarterly by the county, which owns the landfill. (The newer portion of the landfill has liners underneath as well as between the old and new portions of landfill and is not affected by the recent issues.)

Kronlokken said the county had detected the chemicals in the monitoring wells some time ago and began working on solutions, even though the state didn’t require it at that time.

But the corrective action plan the county provided the MPCA must be publicly reviewed and approved by the state before the landfill gets a permit renewal.

Miller said the MPCA is required by statute to hold a public hearing and accept public input for 30 days before it decides whether to give final approval of the county’s plan for mitigating the problem.

Miller said MPCA engineers have reviewed the county plan and saw no problems with it.

She said the agency periodically sees similar problems in older landfills that don’t have liners.

The main chemicals of concern detected in the monitoring wells are tetrachloroethene and trichloralethylene, man-made products that were and are widely used in a variety of ways including dry cleaning, textiles and industrial degreasers.