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1 ' <br /> 1 <br /> January 1993 <br /> (GeoAudit CV43F1-1. 35) <br /> Page 2 of 5 <br /> collected. TPH as gasoline was detected at a concentration of 4, 920 <br />' Ag/1 (ppb) , and benzene was detected at a concentration of 270 gg/l <br /> in the water sample. <br /> On 14 January 1992 , GeoAudit, under the supervision of Mary Meays <br /> of the San Joaquin County Public Health Services - Environmental <br /> Health Division (PHS/EHD) , attempted to sample MW-1. Unfortunately, <br /> the well was dry and no sample could be collected. Depth to water <br />' at the time of well installation (1988) was 65 to 70 feet. Depth to <br /> water in the area is currently 90 to 95 feet. <br /> Additional investigation of the soil and groundwater contamination <br /> was then required by the PHS/EHD. GeoAudit was then retained by <br /> Marlowe Properties to install an additional monitoring well at the <br /> site. <br /> PROCEDURES <br /> DRILLING AND SOIL SAMPLING <br /> On 21 December 1992 monitoring well MW-2 was installed to the <br /> southwest of the former tank excavation, approximately 35 feet from <br /> MW--1 (see Figure 2 - Site Plan) . <br /> The boring was advanced to a depth of 110 feet using a truck- <br /> mounted 8-inch hollow-stem auger rig. The CME-75 drill rig and two- <br /> man crew were supplied by West Hazmat Drilling Corporation. <br /> Discrete soil samples were collected ahead of the drill bit at <br /> five-foot intervals using a split-tube sampler loaded with three <br /> pre-cleaned 2 . 5 by 6-inch brass tubes. To avoid cross <br /> contamination, the sampling equipment was washed in a tri-sodium <br /> phosphate (TSP) solution and rinsed twice with water prior to each <br /> sampling run. <br /> For each sample, both ends of the lead tube were covered with <br /> aluminum sheets, capped and sealed with tape. The samples were <br /> stored on ice pending transmission to a state-certified laboratory <br /> (Alpha Analytical Laboratories in Ukiah) . The samples were analyzed <br /> for total petroleum hydrocarbons (TPH as gasoline and diesel) , <br /> volatile aromatics (BTE&X) and total lead in accordance with EPA <br /> methods 8015, 8020 and 7420, respectively. <br /> Soil from the second brass tube was extruded and screened for the <br /> presence of organic vapors using a photo-ionization detector (PID: <br /> Thermo Environmental 580A, 10. 0 eV, calibrated to isobutylene) . The <br /> soil was then described in accordance with the Unified Soil <br /> Classification System (see Boring Logs) . <br />