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as the final cover system is installed; the system will be modified, as necessary, <br /> and will then be reconnected. <br /> An intermediate liner system is proposed over the existing Austin Road Landfill. <br /> Horizontal collectors, spaced at approximately 200 feet on center, will be <br /> installed to collect landfill gas generated below the liner (see Drawing 13). The <br /> horizontal collector consists of perforated HDPE pipe installed in a gravel pack <br /> below the proposed liner system. A geotextile fabric will be installed in the <br /> gravel trench to prevent fine materials from entering and clogging the collector <br /> pipe. Additionally, the existing vertical landfill gas wells will be cut about 5 feet <br /> below the liner and connected to the horizontal wells with laterals. The <br /> horizontal wells will be extended through the edge of the in-place refuse prism <br /> on the north face to extract landfill gas while the site is filled. When the refuse in <br /> adjacent waste cells reach the height of the horizontal well stub-outs on the <br /> south face, the horizontal well can be extended to collect the gas generated in <br /> the new cells. This end of the horizontal collector will be connected to the <br /> looped header system located along Austin Road's southern boundary. <br /> As the new cells are filled, additional vertical extraction wells will be installed in <br /> phases to control surface landfill gas emissions. These wells may be extended as <br /> the fill progresses in the cell, or may be abandoned and replaced with new wells <br /> when the fill reaches the final grade elevation. <br /> As the fill progresses above the existing and now-lined refuse prisms, additional <br /> vertical extraction wells will be placed into the upper portions of the landfill to <br /> achieve the proper spacing required for surface emissions control. <br /> Permits will be obtained from the San Joaquin Valley Air Pollution Control <br /> District (SJVAPCD) and other appropriate agencies for the construction and <br /> operation of each phase of gas system development. <br /> 5.3 DESIGN CALCULATIONS <br /> 5.3.1 SOIL BALANCE <br /> Soil excavated from each phase (Table 9) will be stockpiled in areas of future <br /> phases or on the former borrow area north of the existing Austin Road Landfill. <br /> This stockpiled soil (estimated total excavation quantities are approximately 4.5 <br /> Forward Landfill JTD 5-13 <br /> L:\Allied\2000.7 93\ReportsUTD-PC PCh1P702:5ec-5-0:5/24/02 <br /> Revision 1:07/16/02 <br /> BRYAN A.STIRRAT&ASSOCIATES <br />