ARCHIVED REPORTS_POST CLOSURE LAND USE PROPOSAL 2014

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