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Foothill Sanitary Landfill Preliminary Closure Plan <br /> Revision 941 May 6, 1994 <br /> Each well will contain three monitoring probes (Figure 5) One <br /> probe will be placed 5 - 10 feet below the surface; a second <br /> probe will be placed at half the depth of the well bore, and a <br /> third probe will be placed at the total depth of the well bore. <br /> Each monitoring well will be drilled to a depth equal to the <br /> maximum depth of the refuse fill within 1000 feet of the well <br /> bore. The monitoring wells will be spaced no greater than 1000 <br /> ft. apart. There will be 5 feet of bentonite at the surface and <br /> between monitoring zones. <br /> The wells will be monitored to determine if gas is migrating off <br /> site, and to determine if the concentration of methane in the air <br /> exceeds a specified level. If the concentration of methane <br /> exceeds 1.25% by volume in landfill structures or 5% by volume <br /> around the perimeter of the landfill, a gas extraction system may <br /> be installed. The gas collected would either be flared off or <br /> used as an energy source as the market permits. <br /> All monitoring wells will have a record containing basic <br /> information. For example, each monitoring well will be shown on <br /> a facility map along with surface elevations at each wellhead. <br /> Also, an as built description will be included, indicating type <br /> of filter pack, thickness and material used for seals, extent and <br /> material used for backfill, size and interval of perforations, <br /> and any shutoff valves or covers. <br /> Landfill gas will be monitored at least on a quarterly basis. <br /> Gas monitoring surveys will be taken within site structures to <br /> determine if methane concentration is in excess of 1. 25%. <br /> Monitoring results will be presented in the form of a report to <br /> the local enforcement agency within 90 days of the sampling <br /> event. The report will include the following items: <br /> 1) The concentrations of the methane at each probe and <br /> within each structure. <br /> 2) The documentation of date, time, barometric pressure, <br /> general weather conditions, and probe pressures. <br /> 3) The names of sampling personnel, apparatus used, and a <br /> description of the methods used. <br /> 4) A numbering system to correlate monitoring results to a <br /> corresponding probe location. <br /> In the event that methane levels exceed the specified limits at <br /> any of the monitoring points, the County will develop a program <br /> to bring the levels into compliance. The program will conform to <br /> Title 14 , Chapter 3 , Article 7 . 8 , Section 17783 . 15 . <br /> 18 <br />