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Ms Margaret Lagorto, SJCP14S September 28,2004 <br /> Dual Phase Extraction Test Report <br /> Joe's Truck Plaza,Lathrop, California <br /> Page 4 <br /> • Sand A is encountered at 5 to 8 feet bgs and is approximately 3 to 10 feet thick, <br /> Sand B is encountered at depths between 25 and 35 feet bgs and is approximately <br /> 7 to 18 feet thick, Sand C is encountered at depths between 50 and 65 feet bgs and <br /> is approximately 15 to greater than 25 feet thick <br /> • Depth to groundwater measured between 6 and 10 feet bgs During the most <br /> recent monitoring event (second quarter 2004) groundwater flow was towards the <br /> north-northwest in the on-site monitoring wells at a gradient of 0 0005, while a <br /> northeasterly flow direction was observed in off-site monitoring wells at a <br /> gradient of 0 0010 ft/ft <br /> SUMMARY OF EXTENT OF PETROLEUM HYDROCARBON IMPACT <br /> • Petroleum hydrocarbons have impacted soil in the vicinity of the UST complexes <br /> and impact extends to the saturated zone <br /> • The highest TPHD (660 mg/Kg), benzene (0 88 mg/Kg) and MTBE (0 46 mglKg) <br /> concentrations were observed in compliance soil samples collected from the <br /> former northern UST pit <br /> • MTBE has been reported in groundwater samples collected from wells MW-1 <br /> through MW-4, MWO-1, MWO-2, and MWO-1X <br /> • The historical highest TPHD, TPHG, benzene, and MTBE concentrations were at <br /> 380 µg/L (MW-4), 480 µg/L (MWO-1X), 3 1 µg/]L (MW-1), and 2,800 µg/L <br /> (MW-1), respectively <br /> DPE FEASIBILITY TEST <br /> The purpose of the feasibility test was to evaluate the viability of using DPE as a <br /> remedial alternative to mitigate the subsurface petroleum hydrocarbon impact to soil and <br /> groundwater The DPE test was conducted between June 14 and 16, 2004, using well <br /> MW-7 The specific objectives of the test were to determine the soil vapor and <br /> groundwater extraction rates, soil vapor and groundwater concentrations, and radius of <br /> influence for both soil vapor extraction and groundwater extraction Details regarding <br /> the test procedures, test equipment, analytical methods, and results of the tests are <br /> presented in the following sub-sections <br /> Prior to conducting the test, SJCEHD and the station manager were informed of the test <br /> schedule and duration Based on our conversations with San Joaquin Valley Air <br /> Pollution Control District (SJVAPCD) personnel, notification to or permits from <br /> SJVAPCD were not required for feasibility tests of duration not exceeding 5-days The <br /> P Voe's Truck PlazalReports\DPE Test\Joes Truck DPE Test Report doe 5 rKA 7215 <br />