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07 June 2012 AGE-NC Project No. 95-0184 Page 4 of 14 Combined with SVE,the IAS method"mechanically/physically"strips volatile hydrocarbons from ground water without the addition of any chemicals or microbe solution into the environment. Deeper soil could be air-sparged, however the rate of the technique must be monitored and mediated to prevent unacceptable migration of the desorbed contaminates. IAS is a widely accepted method of volatilizing hydrocarbons. As IAS has few, if any, adverse environmental effects, it is likely to be more readily approved for implementation by regulatory agencies. Based upon these considerations and the presence of relatively deeper sandy soil at the site, AGE recommends installation of an IAS well network and new soil vapor extraction (SVE)well network, combined with the current SVE remediation system for remediation of impacted ground water and soil in the former UST areas. A minimum 12-month remediation period can be expected to be required to reduce volatile and light-end hydrocarbon concentrations by 70% or 80% to near State of California drinking water standards (benzene). A sparging / extraction system may also have a secondary effect of bioventing impacted soil, increasing the oxygen concentrations available for biologic processes, thereby possibly increasing the natural degradation rate. Ground water in the former UST area may be more effectively addressed by IAS, while ground water outside the direct plume area may be more effectively addressed by attempting to stimulate bioremdiation through sparging to increase dissolved oxygen concentrations. AGE recommends addressing ground water impacted primarily by long chain TPH by encouraging biodegr@dation by increasing dissolved oxygen concentrations. This can be accomplished by installation of sparge points for slow sparging. 3.0. SCOPE OF WORK By letter dated 03 May 2012, the San Joaquin County Environmental Health Department (EHD) requested the preparation of a work plan for the remediation of soil and ground water near the southern UST area to reduce high concentrations of other petroleum hydrocarbon compounds (benzene and 1,2-dichloroethane). 7 ll The purpose of this work plan is to implement ground water remediation tho4ught air- sparging and soil remediation utilizing soil vapor extraction, as an interim remedial option at the Larry's Auto site. Advanced GeoEnvironmental,Inc.