A warning sign around the old Kentwood Landfill.
A warning sign on the fence around the old Kentwood Landfill.

Methane gas seeping out of an old landfill could pose a risk of explosion in nearby houses
, according to Kent County officials.

The county identified methane outside the perimeter of the long-closed Kentwood landfill at 4900 Walma Dr. SE, off Breton Road north of 52nd Street, while recently installing gas monitoring wells, said Dar Baas, public works director. About 150 residences within 1,500 feet of the landfill's western boundary will be getting notices in the mail, he said.

"Methane is not toxic, but it is flammable," Baas said. "The biggest concern is it getting caught up in a building where it might store up and cause a fire.

"What we don't know is how far (the methane is migrating) and that's what we're trying to figure out."

The county's public works department will hold a meeting on the gas 7 p.m. Wednesday, Aug. 31, at Kentwood City Hall, 4900 Breton Ave. SE. Residents also can get free on-site methane testing by the department.

Public buildings adjacent to the landfill have been tested and do not have methane in them, Baas said.

The 72-acre former landfill is one of 88 Superfund sites in Michigan monitored by the U.S. Environmental Protection Agency and the state Department of Environmental Quality. Methane gas was identified in the footprint of the Kentwood Public Library when it was built in 2010, and efforts have been underway to mitigate the threat of gas buildup since then, according to an annual federal report on the site.

Initially, passive venting of methane "didn't prove very effective," said Daria Devantier, a unit chief in the DEQ's Superfund section. An active system of gas wells that suck methane out of the landfill and burn it now is being used.

The county will consider doubling the size of that system in hopes of mining more methane so that it doesn't spread to neighboring properties, Baas said.

"We've got to put more wells in to draw from a larger area," Baas said. "It should put an end to it."

The county recently drilled 11 monitoring wells that found methane in the ground at depths of 5 feet to 50 feet, at concentrations high above flammability levels. The finding shows that methane has spread farther beyond the landfill boundary, but residents don't face any higher risk than they have in the past, said Kristi Zakrzewski, the DEQ's project manager for the landfill.

Local, state and federal officials have known methane to be an issue, and the priority has been to safeguard buildings nearest the landfill, she said. The county and city now are progressing with steps to halt migration of the gas.

Trash customers in Kent County started paying a $1.68 annual surcharge this year to help pay for maintenance of the Kentwood landfill and closed landfills in Sparta and Plainfield Township.