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layer will not be disturbed. The vegetation will be seeded at the beginning of the rainy season, so no irrigation will be necessary. 4.1.3 Groundwater Extraction and Treatment e leachate-impactedoundwater and treatin it to This alternative Involves extracting th gr g reduce concentrations of VOCs to acceptable levels before discharging the treated groundwater. Typical discharge locations include Corral Hollow Creek (with an appropriate National Pollutant Discharge Elimination System [NPDES] permit), wastewater treatment facilities, or spray evaporate over the site (with an appropriate permit from the RWQCB). Several variables affect the feasibility of this alternative, as described below: 9 Aquifer characteristics dictate the number and spacing of extraction wells. Additionally, the aquifer characteristics determine the capacity of the treatment system required. 9 Typical treatment technologies used in the removal of VOCs (COCs found at Corral Hollow Sanitary Landfill) from groundwater are air stripping, granular activated carbon(GAC)adsorption,and ultraviolet/photo-oxidation. 9 Discharge requirements affect both the degree of treatment required (whether secondary treatment or tertiary treatment is required), and the costs associated with operating the treatment system. 9 Air emission restrictions may require air abatement devices for groundwater treatment technologies such as stripping towers. The local geology and hydrogeology of the site is characterized by two water-bearing zones; a shallow perched zone within the Corcoran Clay and a deep regional water- bearing zone approximately 250-300feet beneath the surface. The shallow perched zone does not appear to be extensive,rather it is confined to the eastern half of the landfill. An extraction treatment system could be designed to pump groundwater from the shallow perched zone within the Corcoran Clay layer to the surface for treatment. Given the low permeability and subsequent low pumping rates associated with the formation, it is expected that a significant number of extraction wells (possibly 10 to 20) will be required to provide sufficient flow to attain hydraulic control of the plume(see Figure 3). Since the chemicals of concern are VOCs (chlorinated hydrocarbons), either an air stripping tower or GAC adsorption would be suitable technologies to remove the contaminants. As the concentration of VOCs is relatively low, GAC adsorption will be more economical. SACNN.\PJ0M39\09390031.9$G-94\*:l Rev.0,420/95 0939-003.19 4-3