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r Draft Environmental Impact Repot Page IV.F-15 Forward Inc. Landfill Expansion so as to achieve concentration meeting drinking water standards or to treat the water through activated carbon filters to remove the VOCs. This plan is currently under review by the RWQCB. It is possible that the VOC impacts in groundwater at the existing Austin Road Landfill are attributable to landfill gas. VOC concentrations have been trending downward recently, and leachate analyses from the existing Austin Road Landfill indicate no significant VOCs. VOCs are detected,however, in landfill gas samples. Forward is currently assessing landfill gas and groundwater issues at the existing Austin Road Landfill and, as required by the RWQCB,the last revised Engineering Feasibility Study(EFS) has been prepared for the Corrective Action Program (HA/AEE, 2001)is currently being updated per the recent 2008-0712 Water Board Order. The revised EFS involved review of available data and preparation of a detailed groundwater r flow and transport model to assess the most efficient means of controlling groundwater impacts at the existing Austin Road Landfill. The model incorporated hydrogeologic and hydrochemical information that were collected in previous investigations of the landfill, and included data collected in aquifer pumping tests that were completed at the site. • Based on the groundwater modeling that was completed for the EFS, it was concluded that the most effective response to groundwater impacts at the site would include the following: Enhanced landfill gas extraction. • Continued groundwater pumping from the two groundwater extraction wells along the north side of the facility. • Continued groundwater treatment using the facility's air-stripper unit. • Artificial recharge of the aquifer by treated groundwater Artificial recharge of the aquifer by treated groundwater was recommended over increased remedial pumping because the re-introduction of pumped water to the aquifer is expected to minimize the impact on an already overdrafted aquifer and would avoid increased energy consumption associated with increased pumping. In combination with plans for an enhanced landfill gas collection system, re-introduction of treated water to the aquifer is expected to reduce existing VOC impacts below Maximum Contaminant Levels(MCLS) (drinking water standards)within five years and below the Water Standard (1 part per billion) within nine years. Project Area Groundwater Quality The source of the groundwater contamination at the Forward and Austin landfill units is fairly well understood,being attributed first and foremost to contamination originating from chemicals are leached out over time form the refuse that accumulated at the landfills. In the case of the unlined Forward unit, the leachate generate had a more direct path to the subsurface environment and groundwater, not initially having the protective leachage collection system that the Forward unit did. The most prevalent and persistent of these chemicals of concern are the chlorinated solvents (referred to as VOCs), common to hundreds of consumer products. The VOCs can be retained in solid state media (by adhering to clay particles as they move down in the unsaturated zone), in soluble form(as a dissolved fraction in surface water or groundwater),or in the form of a gas (circulating in the flux of the other common landfill gases, methane and carbon dioxide). The VOCs can transform easily from the solid, soluble, or gas form depending on the circumstances. Thus, the origin of the VOCs in the water that creates the landfill leachate is likely the result of a long process of household hazardous waste containing common solvents such as PCE and TCE leaching into the environment.