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R 4 <br /> ' Nfl�IC�'+IfA�fR <br /> T Mr. Charles Leub-er <br /> 6 December 1990 <br /> Page 3 <br /> each of the excavations. One sample was collected at each corner of the excavation, <br /> immediately adjacent to the edge of the concrete slab. Each of these samples was <br /> collected at a depth of approximately two feet into the native soils beneath the level of <br /> ole <br /> the bottom of the tank. One sample from each excavation waackhammer mounted onhthe <br /> that was punched in the center of the concrete slab using a j <br /> backhoe arm. This sample was collected at a depth of one to two feet into the native soil <br /> beneath the bottom of the concrete slab. Table 1 summarizes the locations of the samples <br /> - collected for laboratory analysis. <br /> The two samples collected from the center o the excavations were collected by attaching <br /> a core sampler to lengths of auger extension rods. The core sampler was then lowered into <br /> the hole that had been punched in the bottom of the concrete slab and driven into the <br /> native soil with a slide-hammer attached to the opposite end of the extension rods. Once <br /> the care sampler was removed from the excavation the brass liner containing the sample <br /> was removed from the sampler and prepared for transport to the laboratory using the <br /> protocol outlined above. Soil samples from beneath the piping were collected in a similar <br /> manner. <br /> LABORATORY ANALYSIS <br /> The analytical program for the soil samples collected from the 10,000 and 6,600 gallon <br /> diesel tank excavation consisted of the following analyses, as specified by San Joaquin <br /> County in their permit to remove the underground tanks <br /> Analysis Method <br /> Total Extractable Petroleum Hydrocarbons GC-FID with soxhlet sample <br /> preparation <br /> Benzene, Toluene, Ethylbenzene and EPA Method 8020 <br /> Xylene <br /> At the same time that a sample was collected for laboratory analysis, a sample was <br /> onitor for the res,�Mce ofrganic vapors. The <br /> collected from the backhoebucket <br /> the pr <br /> shown <br /> organic vapors is <br /> results of laboratory analyses and field Monitoring for <br /> shown in Table 1. <br /> EVALUATION of SOIL SAMPLING*RESULTS <br /> A leaching potential analysis was performed for each of the tanks on the site,base on the <br /> method outlined in the Oahe Leakng Underground Fue <br /> nob pten8iai analysis199 version Of for the 10i 000 gallon diesel tank is showI Tank n in <br /> Field Manual. The leach g p <br />