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County of Riverside <br /> <br /> 3 <br />October 26, 1993. The post-closure elements of the plan describe the requirements for various <br />environmental monitoring controls on the property. These include the following controls: <br /> Cover system <br /> LFG flare station and extraction system <br /> LFG probes <br /> Ground water monitoring network <br /> Drainage facilities <br /> <br />The purpose of the cover system is to isolate the waste placed in the landfill from humans and <br />the environment. The foundation layer serves as a base for construction of the low permeability <br />layer, which limits infiltration of precipitation and release of landfill gas to the atmosphere. The <br />vegetation layer is an erosion resistant layer intended to protect the low permeability layer from <br />desiccation and erosion. The vegetative layer is planted with grass which helps to prevent the <br />layer from eroding. Periodic inspections of the cover system are required under the Post-Closure <br />Maintenance Plan. <br />LFG flare and Extraction System <br />Landfill Gas (LFG) is the result of waste decay. The rate of generation varies depending on a <br />number of parameters including organic content, moisture present, and the age of waste. The <br />older the waste is, the lower the rate of LFG generation. A network of LFG extraction wells was <br />installed in March 1989. LFG is extracted from within the waste to prevent a buildup of pressure <br />and the potential for migration out of the landfill boundaries. The extraction system consists of <br />45 vertical wells (WH 1 to WH 42 and GS 1 to GS 3), a system of connecting piping and <br />approximately 90 standard cubic feet per minute (SCFM) LFG flare station where the gas is <br />burned under the requirements of South Coast Air Quality Management Permit-to-Operate <br />(PTO) requirements. The LFG system is monitored and maintained in accordance with the PTO. <br />LFG probes <br />CCR Title 27 requires the monitoring for the presence of LFG at the property boundary of the <br />Landfill. The monitoring probes extend into the native soil outside the waste mass and are used <br />to measure the effectiveness of the LFG collection system. They also serve the purpose of <br />detecting LFG migration outside the property which exceeds 5 percent methane volume/volume. <br />The spacing and depths of the LFG probes vary. There are a total of 51 LFG perimeter <br />compliance probes (P 1 to P 51) located around the Landfill as shown on Figure 6. <br />Groundwater Monitoring Network <br />There are seven groundwater monitoring wells RG-1 to RG-6. They are monitored, sampled, <br />and tested according to the Waste Discharge Requirements (WDR) No. 98-99-02. The <br />frequency of monitoring and reporting is semi-annual. Figure 6 shows the locations of the <br />groundwater wells. <br />