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5. The Counties performed another soil -gas survey in May 1993 at 28 locations in and around the landfill. The two soil -gas surveys combined indicate high concentrations of methane in these areas: • primarily along the landfill's west and northwest boundary • beneath several properties west of Jamaca Avenue No methane or only trace amounts were found in the shallow soils in the residential area northwest of the landfill; along the landfill's southern and eastern boundaries; and at all other locations surveyed off - site. 6. Based on the soil -gas survey and discussions with the EPA, MPCA, and Minnesota Department of Health, the Counties installed continuous methane monitors in six homes and the Lake Elmo Maintenance Building in July 1993; these are in addition to the fire station monitor. No methane alarms have been activated at any of the sites. WHAT'S THE SOLUTION? With the help of an engineering consulting firm, the Counties did a feasibility study to find the best approach to correct the methane gas problem; the study considered site conditions such as geology, existing research, and EPA's requirements. The recommended solution is an "active barrier extraction vent system." A pilot study --among the first of its kind in the country --confirmed that the system would satisfy the EPA and protect off -site homes and buildings. Construction of the system is scheduled to begin October 4 and end November 30, 1993, with operation beginning soon after. HOW DOES THE SYSTEM WORK? Fourteen extraction vents are being installed on the edge of the landfill (primarily at the western boundary) to capture methane migrating toward homes and municipal buildings. Thes ' vents are made by drilling holes 12 inches in diameter and an average of 40 feet deep and installing a screeZ, pipe in the holes. At the surface the vents will be connected with a piping system leading to a small building; inside are blowers which draw landfill gas from the soil through the piping system. The collected gas will then be discharged at the surface.near the center of the landfill. WHAT WILL BE THE RESULT? During startup, contaminant concentrations in the gas will be determined and flow rates will be balanced to optimize performance of the system. Methane gas levels in the monitoring vents will be evaluated regularly to ensure that EPA standards are met on -site and at the site boundary. This information will also be used to assure that. the gas discharged from the system meets all state and federal air quality standards and poses no health risk. Although landfill gas usually has an odor, it is expected to be unnoticeable beyond the discharge area. The real danger with methane gas is when it concentrates and builds up to explosive levels, so dispersing the gas in the open air poses minimal risk. It is important to note that no additional landfill gas will be collected and discharged to the air than occurred naturally; the central difference is that, instead of allowing the gas to potentially enter buildings and pose a threat, the system is collecting that gas and discharging it at the landfill itself. For more information, please contact Eric Magee at 430-6686 for the Counties or Larry Schmitt (3121353-6565) or Derrick Kimbrough (3121886-9749) for the U.S. EPA. If you need assistance due to disability or language barrier,please call 430-6655 (TOO 439-3220). Equal Employment Opportunity/Affirmative Action