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. CHRONOLOGY <br /> Shell-branded Service Station <br /> 341 East MainStreet <br /> Ripon, CA 95366-2901 <br /> 04/24/96 Three underground storage tanks (USTs) were removed from the site on <br /> this date under permit issued by San Joaquin County Environmental <br /> Health Department (EHD). Soil samples were collected beneath the UST <br /> and dispenser system. High concentrations of gasoline constituents were . <br /> detected in three soil samples (S=2 at 9 feet below surface grade (bsg),X-1 <br /> at 15 feet bsg , and X-2 at 18 feet bsg). <br /> 04/24/96 EHD filed Unauthorized Release Form URF #96-U16 on this date. <br /> 04/24/96 EHD filed Notification of Hazardous Waste Discharge on this date. <br /> 03/23/98 Date that monitoring well MW-1 was installed onsite; the well's total . <br /> depth was 35 feet bsg. <br /> 04/30/98 Date of report on installation of MW L <br /> 07/10/98 Date of Investigation Work Plan. Addendum #4 that contains completed <br /> conduit and well surveys. A domestic well (Den Dulk Well) and a <br /> CalTrans irrigation well were located within 300 feet of this site. The <br /> groundwater from these wells was sampled for total petroleum <br /> hydrocarbons as gasoline (TPH-g); benzene, toluene, ethylbenzene, total <br /> .xylenes (BTEX); Methyl tertiary-butyl ether (MTBE); ethyl tertiary butyl <br /> ether (ETBE); di-isopropyl ether (DIPE); tertiary butyl alcohol (TBA); <br /> tertiary-amyl methyl ether (TAME); ethanol, and.methanol. The results <br /> were non-detect for contaminants. Seven municipal wells, two domestic <br /> wells, and the Stanislaus River Were identified as located within a half- <br /> mile radius of this site. <br /> 07/14-17/98 Ten cone penetrometer test (CPT) borings (CPT 1-10) were advanced on- <br /> and off-site during this time. MTBE was detected at 27 .milligrams per <br /> kilogram (mg/kg) in soil samples collected from_Cl-S-29 at 29 feet bsg. <br /> Also, MTBE was detected in grab groundwater samples collected from <br /> CPT-1 at 32 and 46 feet bsg at 170,000 micrograms per liter (µg/L) and <br /> 120 µg/L; respectively; and from CPT-2 at 32 and 40 feet bsg at 330 µg/L <br /> and 11,000 µg/L, respectively. <br /> 08/17/98 Date of CPT Investigation Report on July 1998 work. <br /> 01/29/99 The site entered the Local Oversight Program (LOP) on this date. <br /> 02/23-25/99 Monitoring wells MW-2, MW-3, and extraction wells EW-1, EW-2 were <br /> installed during this time. <br /> I <br />