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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.
START and U.S. EPA On-Scene Coordinator Walter Neid continued air monitoring of homes along the Mallard Lake Facility. On November 19, 2007 START, U.S. EPA along with PRP consultants STS and the two personnel from the Hanover Park Fire Department screened 6 out of 12 residences along County Farm road and a subdivision south of Schick Road. N0 explosive levels were detected in any of the homes.
On November 20, 2007, START, U.S. EPA and STS screened 9 out of 29 homes along Lawrence Avenue, County Farm Road and homes that were not screened on November 17, 2007 on Whitney Drive. U.S. EPA Community Involvement Coordinator Mike Joyce provided a letter to residences explaining the purpose of the residential monitoring. No elevated levels or explosive levels were detected.
• Continue Screening of homes in residential homes to the west of Mallard Lake Facility including Goddard and McCormick Lane. Initiate sampling of shallow soil gas near residential homes.
• Expand the investigation to determine the extent of the landfill gas. Sample the ground water in the temporary wells.
• Work with the landfill owner/operator to prepare a corrective action for the landfill gas migrating off-site.
• Propose an immediate remedial system to mitigate the potential migration of methane gas into nearby residences including sub-slab investigations.
• Continue residential screening of homes along the Mallard Lake Facility.
• Install explosive gas detectors in residential homes
• Propose and/or implement short-term remedial system to mitigate the potential migration of methane gas into nearby residences until a more thorough investigation of the methane migration is conducted.
• Many residents were not home during screening activities on November 19 and 20, 2007, or declined the screening.
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