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r.. 3.0 Proposed Remedy 3.1 Proposed Remedy Approach In May 1992, a SVE test was performed by extracting soil vapor from MW-10 and monitoring the vacuum response in MW-1 through MW-4. In August 1996, a second SVE test was performed in August 1996 by applying a vacuum to VW-1 and recording data for VM-1 and ,-, VM-2. The documents summarizing these tests were reviewed and used to design the proposed system. SVE is effective at removing volatile and biodegradable compounds from permeable subsurface soils. Generally, the soils at this site are silts, silty sands and clayey sands. No soils were #.• described as clays and only small volumes were classified as silty clay. Therefore, SVE is appropriate for remediation of volatile petroleum hydrocarbons in soil. Typically, semi-volatile �. petroleum hydrocarbons in soil will biodegrade in soil if sufficient oxygen and moisture are present. Because natural attenuation of the subsurface petroleum hydrocarbons at the site has been observed, addition of atmospheric oxygen to the subsurface is expected to accelerate degradation of the semi-volatile petroleum hydrocarbons. �.` While SVE is effective for soil remediation, it is less effective for petroleum hydrocarbons already in groundwater because the atmospheric oxygen must diffuse into the groundwater. By injecting atmospheric oxygen into the groundwater by air sparging, the transfer of oxygen into the groundwater is more effective. Along with air sparging, SVE is used to capture the petroleum hydrocarbons volatilized from the groundwater by the passing air. Based on the site conditions, air sparging and SVE are proposed for remediation of the petroleum hydrocarbons in the soil and groundwater. 3.2 Proposed Clean-up Goals To design the system, it was necessary to define the impacted area above clean-up goals. The proposed clean-up goals are the following: • For soil, the proposed clean-up goal is 100 mg/kg for TPHg and 1.5 mg/kg for benzene. • For groundwater, the proposed clean-up goals are MCLS. These include 0.001 mg/L for benzene, 0.15 mg/L for toluene, 0.7 mg/L for ethylbenzene, and 1.75 mg/L for xylenes. sAcnP r�. aizoo2P&V rsWate�zsI aanxbc 3-1 (aroza000�