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• It is possible that the VOC impacts in groundwater at the existing Austin Road <br /> Landfill are attributable to landfill gas. VOC concentrations have been trending <br /> downward recently, and leachate analyses from the existing Austin Road Landfill <br /> indicate no significant VOCs. VOCs are detected, however, in landfill gas <br /> samples. Forward is currently assessing landfill gas and groundwater issues at <br /> the existing Austin Road Landfill and, as required by the RWQCB, a revised <br /> Engineering Feasibility Study (EFS) has recently been prepared for the Corrective <br /> Action Program (HA/AEE, 2001). <br /> The revised EFS that was completed by HA/AEE involved review of available <br /> data and preparation of a detailed groundwater flow and transport model to <br /> assess the most efficient means of controlling groundwater impacts at the <br /> existing Austin Road Landfill. The model incorporated hydrogeologic and <br /> hydrochemical information that were collected in previous investigations of the <br /> landfill, and included data collected in aquifer pumping tests that were <br /> completed at the site. <br /> Based on the groundwater modeling that was completed for the EFS, it was <br /> • concluded that the most effective response to groundwater impacts at the site <br /> would include the following: <br /> • Enhanced landfill gas extraction. <br /> • Continued groundwater pumping from the two groundwater extraction wells <br /> along the north side of the facility. <br /> • Continued groundwater treatment using the facility's air-stripper unit. <br /> • Artificial recharge of the aquifer by treated groundwater. <br /> Artificial recharge of the aquifer was recommended over increased remedial <br /> pumping because the re-introduction of pumped water to the aquifer is <br /> expected to minimize the impact on an already overdrafted aquifer and will <br /> avoid increased energy consumption associated with increased pumping. In <br /> combination with plans for an enhanced landfill gas collection system, re- <br /> introduction of treated water to the aquifer is expected to reduce existing VOC <br /> impacts below Maximum Contaminant Levels (MCLS) (drinking water standards) <br /> within five years and below the Water Standard (1 part per billion) within nine <br /> years. <br /> • <br /> Forward Landfill JTD 3-17 <br /> L-\Allied\2000.193\Reports�td:Sec-3.0:05/21/02 <br /> BRYAN A.STIRRAT&ASSOCIATES <br />