U.S. EPA’s Emergency Response Branch was requested to assist the IEPA in March of 2007 at the Wayne Township Ground Water site in Northern DuPage County, Illinois. Approximately 60 residential wells were sampled by the DuPage County Health Department in 2005 and 2006 and were found to be contaminated with vinyl chloride above the Removal Action Levels. Many of the homes have been hooked into a Lake Michigan Water Supply where municipal water lines were available.
U.S. EPA upon reviewing available data and well logs from the Mallard Lake Landfill discovered a boring with methane levels of 17.9% concentration within 50 feet of a residential neighborhood on the West perimeter of the landfill. U.S. EPA and IEPA requested the BFI and DuPage Forest District to conduct an investigation outside the West boundary, South Boundary and on the Right-of Way to determine the extent of the gas migration off site. This landfill gas has historically contained high levels of Volatile Organic Compounds including vinyl chloride which was reported by the landfill operator to lead to ground water contamination exceeding the Maximum Concentration Limit (MCL) for vinyl chloride at the Western perimeter of the landfill. .
During the first phase of the investigation conducted November 6-10, 2007, high levels of methane exceeding 75% in concentration were detected in temporary monitoring wells at locations within 30-50 feet from residential homes. The permeable zone containing this methane is 40-45 beneath the ground surface. Other permeable zones exist near the ground surface and will be monitored in the second phase of the sampling. Additional locations have been proposed in the residential neighborhood west of the landfill. There is a great concern for migration of this methane and VOC’s to enter the homes via vapor intrusion pathways. Water and VOC samples will be collected from the temporary wells in the next two weeks.
During the first phase of the site investigation, conducted November 6-10, 2007, high levels of methane vapor, exceeding 75%, were detected in the headspacees of temporary monitoring wells at locations within 30-50 of residential homes. There is a great concern for migration of methane and VOC vapors into nearby homes via vapor intrusion pathways.
