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Prior to placement of the final cover, the header system will be removed. In <br /> order to minimize interruption of the system operation, the header will be <br /> removed in phases with each phase re-installed and made operational prior to <br /> removal of the next phase. Any affected wells will be disconnected prior to <br /> removal of the header. Headers can be re-installed if the integrity of the pipe <br /> remains intact and if it can be adjusted to a positive grade. Otherwise, the <br /> pipelines must be replaced. The main header system will remain on-line during <br /> the entire construction period. <br /> Any deep or shallow vertical gas collection wells in place at closure will be <br /> protected during the placement of the final cover since control of landfill gas <br /> must continue during cover construction. The top of the vertical or horizontal <br /> wells will be extended through the final cover and then reconnected to the <br /> lateral header line as before. Any damaged or non-functional vertical wells will <br /> be abandoned and new replacements installed to provide gas extraction <br /> coverage. Final cover material will be placed and compacted by hand around <br /> the wells or vaults to protect against damage by earthmoving equipment. The <br /> condensate will drain along the subheaders and main headers to collection <br /> sumps. When the headers are re-installed after final cover construction they will <br /> again gravity drain back to the collection sumps. <br /> 3.9 LANDFILL GAS MONITORING SYSTEM <br /> 27 CCR, Section 20925 requires that subsurface gas monitoring wells (probes) <br /> be installed as part of closure around the perimeter of the landfill within the <br /> property limits but outside the limits of refuse with a spacing of approximately <br /> 1,000 feet. As discussed in Section 2.1, the existing gas migration monitoring <br /> system consists of 18 probes located as shown on Drawing 13 of the JTD. As <br /> part of closure, the existing probes will be protected in place. <br /> 3.10 GROUNDWATER/SURFACE WATER MONITORING SYSTEM <br /> Groundwater monitoring programs are currently being implemented on a <br /> quarterly basis at the existing Forward and Austin Road Landfills, as discussed in <br /> Section 2.2. Figure 2 shows the location of the existing groundwater monitoring <br /> ® wells. This monitoring network may later be expanded during the active landfill <br /> life and will be maintained throughout the post-closure period. <br /> Forward Landfill PCPCMP 3-13 <br /> L:\Allied\2000.193\Reports\FinaiPCPCMP:FL-sec3.doc:5/21/02 ®RYAN A.STIRRAT a ASSOCIATES <br />