Environmental Progress - Summer 1999

Methane Gas Buildups Force Residents From Homes

Colorless, odorless gas from nearby landfill posed risk of fires.

High levels of potentially flammable methane gas migrating from a nearby Superfund site caused the temporary relocation of five families in the Boone County community of Belvidere last April.

The problem was discovered after the Illinois EPA requested that gas monitoring wells be installed near the Wycliffe Estates housing development, as part of the ongoing remedial investigation of the abandoned MIG/DeWane landfill. The landfill has been identified as a Superfund site.

The wells were installed in March 1999, and the following month, the Illinois EPA received results from the wells. The high methane levels detected immediately raised concern that the gas could already have reached homes immediately nearby and begun to collect in basements where it would create a fire hazard.

Creation of a mixture of gases is normal at landfills, as part of the natural decay process. The colorless, odorless gas is flammable at high concentrations and the gases can travel underground, especially through geological layers of sand or gravel. As the gases build pressure inside a landfill, they seek escape.

Landfills today typically have gas collection systems that relieve pressure and route gas to a flare or electric generation facility. The MIG/DeWane landfill was abandoned before such a system was installed. The housing development was later built near the landfill.

Landfill gas had set a record for underground travel.

Conference calls with Bevidere city officials the day the monitoring results were received led to arrival of Illinois EPA the following day to perform immediate air sampling in the Wycliffe Estates. Members of the national priorities list unit, the office of community relations and the Rockford field office worked with members of the Belvidere fire department, the Boone County Health Department, and a private consulting firm representing the landfill's responsible parties. As sampling progressed, the Illinois Department of Public Health and local emergency coordinators were also consulted, and it was decided to recommend evacuation of families in six homes where high methane levels were detected in basement sump pits.

Dark red monitors stand behind homes plagued by high methane levels linked to a nearby landfill in Belvidere.

The most distant of the evacuated homes is approximately 1,000 feet from the landfill, making this the farthest landfill gas is known to have traveled underground in Illinois.

Five of the six families opted to move for a few days into temporary housing. Funding initially came from the Red Cross, and later was provided by the subdivision's developer.

A serious problem but relatively simple to solve

Although the presence of the gas in the homes was unusual and unexpected, the short term remedy is relatively simple. Field-fabricated, explosion-proof ventilation systems were installed in the sumps of the six homes of most concern, and continuous methane gas monitors have been installed in the basements of more than 30 subdivision residences. These monitoring units have been offered to all subdivision residents.

In the long term, the gas must be removed and prevented from reaching the nearby homes. A gas extraction system that includes extraction wells near the development and an interception trench bordering the landfill will collect gas and route it to a flare. A version of this system, originally intended as part of the long-term corrective process, has now been installed and is operating. Levels of methane have been significantly lowered.