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2057 South El Dorado <br /> Stockton, CA <br /> Page 2 <br /> By separate letter dated June 15,2005,AGE stated it is in opposition to interim remediation <br /> using in-situ air sparging (IAS), or combination of IAS/SVE, due to potential mobilization <br /> of the volatized contaminants laterally, or parallel to the aquifer due to the abundance of fine <br /> grained sediments in the upper strata, and the predicted poor SVE recovery of the volatiles <br /> liberated from the dissolved phase. EHD agrees with AGE that IAS, or combination <br /> technology of IAS/SVE, does not appear to be a feasible technology at this time. However, <br /> the above-mentioned, stand-alone SVE pilot test should be conducted to evaluate SVE <br /> suitability for potential interim remediation of the vadose zone. Analytical results of the soil <br /> samples collected at 14 feet bsg during the tank removal in 1999 included contaminant <br /> concentrations as high as 190 milligrams per kilogram (mg/kg) of MTBE and 2,100 mg/kg <br /> of TPH-g,and subsequent results of groundwater samples from monitoring wells were as <br /> high as 110,000 micrograms per liter (ug/1) of methyl tert butyl ether (MTBE) in MW-1, and <br /> 260,000 ug/l of total petroleum hydrocarbons as gasoline (TPH-g), and 5,600 ug/l of <br /> benzene. If a significant amount of contaminants still exists in the vadose zone,it should be <br /> a high priority to remove as much of the contaminant mass as is cost-effective before the <br /> contaminant mass further dissolves into and degrades the groundwater. <br /> Please feel free to contact Jeffrey Wong at (209) 468-0335 if you have any questions. <br /> Donna Heran,REHS, Director <br /> Environmental 1jealth Department <br /> Jeffrey Wong, Senior REHS Nuel C. Henderson,Jr.,PG <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> Cc: CRWQCB, Central Valley Region—James L. L. Barton,PG <br /> Cc: Advanced GeoEnvironmental, Inc. —Donna Sexton <br />