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Tosco Corporation,a subsidiary of Plullips Petroleum Company 2 <br /> Tosco Station#11192, I403 Country Club Lane,Stockton,CA February 13,2002 <br /> • In April 2001, GR conducted a subsurface investigation by advancing eight off site and <br /> two on site GeoprobeT?" bonngs and one Cone Penetration Test (CPT) Laboratory <br /> analysis for soil samples submitted did not detect gasoline range total petroleum <br /> hydrocarbons (TPHg), benzene, toluene, ethylbenzene, total xylenes (collectively <br /> BTEX), or MtBE above laboratory detection limits Analyses of grab groundwater <br /> samples collected from boring CPT-1 at 75 feet below ground surface (bgs) reported <br /> maximum concentrations of MtBE at 120 parts per billion (ppb) TPHg and BTEX were <br /> not detected above laboratory detection limits in any grab groundwater sample analyzed <br /> (GR, 2001) <br /> In April 2001, GR conducted a well search in a t/2 male radius of the site Three <br /> municipal wells were identified, with the closest being approximately 100 feet north- <br /> northwest of the site (GR, 2001) <br /> Between August 8 and 10, 2001, GR installed three two-inch diameter off site <br /> groundwater monitoring wells (MW-8 through MW-10) and one two-inch diameter on <br /> site groundwater monitoring well (MW-11) Wells MW-8 through MW-10 were <br /> installed to depths from 28 feet to 29 feet bgs Well MW-11 was installed to a total depth <br /> of 79 feet bgs with an 8 5 inch steel conductor casing extending from approximately 1 <br /> foot bgs to 53 feet bgs Laboratory analysis for soil samples submitted detected MtBE in <br /> one sample (MW-I1 at 14 feet bgs) at a concentration of 17 parts per million (ppm) <br /> TPHg, BTEX, Di-isopropyl ether(DIPE), tertiary-Amyl methyl ether(TAME), Ethyl <br /> •; tertiary-butyl ether(ELBE), and tert-Butyl alcohol (TBA) were not detected above <br /> laboratory detection limits Laboratory analysis for groundwater samples submitted <br /> detected MtBE in one sample (MW-11) at a concentration of 110 ppb TPHg, BTEX, <br /> DIPE, TAME, ELBE, and TBA were not detected above laboratory detection limits in any <br /> groundwater samples analyzed (GR, 2001) <br /> DPE OPERATION <br /> Pre-Test Activities <br /> Prior to initiation of field activities, SECOR obtained authorization to perform the DPE <br /> test from San Joaquin Valley Unified Air Pollution Control District SECOR also <br /> prepared a site-specific Health and Safety Plan (HASP) The HASP is required by the <br /> Occupational Health and Safety Administration (OSHA) "Hazardous Waste Operations <br /> and Emergency Response" guidelines (29 CFR 1910 120), and by California <br /> Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste <br /> Operations and Emergency Response" guidelines (CCR Title 8, Section 5192) The <br /> Health and Safety Plan was reviewed by field staff and contractors prior to the beginning <br /> of field operations at the site <br /> DPE Summary <br /> . SECOR performed DPE at the site on December 3rd through December 7a', 2001 DPE <br /> was performed using a 20 hp liquid ring vacuum pump connected to a H2 Oil Thermal <br /> Oxidizer(Therm-ox) for treatment of the extracted soil vapors prior to discharge to the <br />