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Site History 14000 Highway 88 Lockeford CA Time Oil Property No 04-049 1 Groundwater Extraction with Soil Vapor Extraction (SVE) SECOR estimates that sod impacts could be adequately addressed by SVE within 2 years, however, groundwater extraction could require up to 10 years to adequately address site impacts Costs to remediate the site using groundwater extraction with SVE would amount to$375,000 2 Air Sparging with SVE SECOR estimates that soil and groundwater impacts could be adequately addressed by air sparging and SVE within 2 years Costs to remediate the site using air sparging with SVE would amount to$150,000 3 Natural Attenuation SECOR estimates that soil and groundwater impacts would naturally attenuate within 20 years Costs to monitor natural attenuation for 20 years would amount to$215,000 SECOR selected air sparging with SVE as the most efficient and cost effective remediation technology to address soil and groundwater impacts associated with the subject site SVE will remediate unsaturated soils by removing soil vapor and volatilizing hydrocarbons sorbed to soils, while air sparging will remediate saturated soils and groundwater by volatilizing dissolved hydrocarbons SVE and air sparging will also result in enhanced biodegradation of hydrocarbons by introducing additional oxygen to the impacted areas Conceptual Remediation System Design During a soil vapor extraction test conducted in March 1998, TPHg concentrations in influent samples ranged from 139 ppmV to 179,000 ppmV Based on influent concentrations SECOR estimates that TPHg removal rates for extraction wells W-1 through W-8 would range from 1 1 lbs/day to 1,425 lbs/day Based on site lithology, flow rates, and data collected during the site investigations, the radius of influence per well was estimated to be approximately 50 feet SECOR estimates that a total of ten existing wells (W-1 through W-8, MW-1 and MW-3) can be incorporated into a vapor extraction system which would influence the entire plume of impacted soil and nearly the entire plume of impacted groundwater Recovered hydrocarbon vapors would be destroyed with a catalytic oxidizer with a destruction efficiency of at least 95% If needed, MW-5 and MW-2 could be incorporated into the system at a later date To date, air sparging pilot testing has not been performed, however, it is SECOR's opinion that air sparging is generally effective in lithologies where SVE is effective A total of four air sparging wells would be installed within the plume of impacted groundwater Each of the wells would be constructed with the top of the well screen located at approximately 3 feet below historical low groundwater levels An air compressor would be used to introduce air into the sparging wells, and vapors would be recovered and destroyed with the SVE system SECOR estimates that the proposed system can be installed within 16 weeks of approval of the fina[ remediation system design The system would be operated until appropriate cleanup goals have been achieved A copy of SECOR's "Corrective Action Pian" dated September 8, 1998, was forwarded to the appropriate regulatory agencies on September 14, 1998 The County approved the plan in faxed correspondence dated September 29, 1998 20