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Mr. Hank Gonzales <br /> October 8, 1992 <br /> Page 2 <br /> notified and a utility clearance of all proposed sampling locations was conducted by <br /> a McLaren/Hart Senior Associate Geoscientist. All field activities were directed by <br /> a McLaren/Hart Senior Associate Geoscientist under the supervision of a <br /> McLaren/Hart Senior Geoscientist. <br /> Soil borings SB-1 and SB-2 were drilled with a Mobile B-57 rig equipped with 8-inch <br /> outside diameter hollow stem auger. The soil borings were drilled vertically to <br /> sample soils near each end of the tank. Soil samples were collected from the borings <br /> at approximately five-foot depth intervals using a 2 1/2-inch outside diameter <br /> modified California split spoon sampler lined with three clean 2-inch diameter brass <br /> tubes. The sampler was driven ahead of the lead auger and drill bit into undisturbed <br /> soil using a standard 140-pound hammer. The number of blows required to drive <br /> each brass tube 6 inches into the soil was recorded. <br /> To prevent potential cross-contamination between soil boring locations,all down-hole <br /> equipment (auger flights, drill bits and split spoon samplers) was decontaminated by <br /> steam cleaning prior to drilling each soil boring. Soil sampling equipment (split <br /> spoon samplers and brass sleeves) was thoroughly washed using a brush and a <br /> solution of Alconox" (a non-phosphate soap). The sampling equipment was then <br /> rinsed with tap water. The tap water rinse was followed by a distilled water rinse. <br /> Immediately after the sampler was retrieved from the borehole, the ends of the lower <br /> tube were sealed with Teflon sheets and plastic end caps and were taped closed. <br /> The sample tubes were then labeled, placed in resealable plastic bags, and stored in <br /> a thermally insulated chest with ice. Samples were delivered to McLaren <br /> Environmental Laboratory in Rancho Cordova under McLaren/Hart chain-of-custody <br /> protocols for analysis or archiving on the day of sample collection. <br /> A portion of the soil in each middle brass tube was sealed in a plastic bag and <br /> field-screened for diesel occurrence by visual inspection for soil discoloration, <br /> olfactory evaluation for petroleum odors, and headspace analysis. Headspace <br /> analysis is a field measurement of volatile organic compounds (VOCs)which are lost <br /> from a soil sample into the head space of the plastic bag. Headspace analyses were <br /> performed on soil samples using a 10.2 electron volt photoionization detector (PID) <br /> after placing the soil sample in the sun for a few minutes and allowing the sample <br /> to equilibrate with the air inside the bag. The PID probe was inserted into the bag <br /> and measured instrument response relative to an isobutylene standard. <br /> Fmcaren <br /> � w Hart <br />