ARCHIVED REPORTS_2002_3 JTD - Laserfiche WebLink

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• LFGES may be independent of the existing system utilized by Ogden Pacific Power. The proposed LFGES may be installed below or above grade. The LFGES will be installed in phases as the landfill expands. Landfill gas not utilized by the power generation facility will be collected, conveyed and incinerated in an enclosed ground flare. The proposed flare station location is identified on Drawing 13. The looped gas header system will allow the operator to divert the landfill gas in the opposite direction when the gas extraction system requires upgrades, maintenance, or repairs by shutting isolation valves. Only a very small portion of the extraction system would be taken off-line while maintenance is being performed, minimizing the potential impact of surface emissions and subsurface landfill gas migration. Under normal operation, the looped header design will allow landfill gas to be routed through both of the extraction headers and significantly reducing the required line sizes. The proposed LFGES includes horizontal and vertical wells to comply with regulatory standards. As the landfill expands, it is anticipated that most of the • system will be installed, with the balance of the system completed as part of closure. During closure construction, the system will be taken off line in phases as the final cover system is installed; the system will be modified, as necessary, and will then be reconnected. An intermediate liner system is proposed over the existing Austin Road Landfill. Horizontal collectors, spaced at approximately 200 feet on center, will be installed to collect landfill gas generated below the liner (see Drawing 13). The horizontal collector consists of perforated HDPE pipe installed in a gravel pack below the proposed liner system. A geotextile fabric will be installed in the gravel trench to prevent fine materials from entering and clogging the collector pipe. Additionally, the existing vertical landfill gas wells will be cut about 5 feet below the liner and connected to the horizontal wells with laterals. The horizontal wells will be extended through the edge of the in-place refuse prism on the north face to extract landfill gas while the site is filled. When the refuse in adjacent waste cells reach the height of the horizontal well stub-outs on the south face, the horizontal well can be extended to collect the gas generated in the new cells. This end of the horizontal collector will be connected to the • looped header system located along Austin Road's southern boundary. Forward Landfill JTD 5-12 L•\A Ili ed\2000.193\R eports\jtd:S ec-5.0:05/24/02 BRYAN A.BTIRRAT 8 ASSOCIATES