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Boring D-4 (Exhibit 9) was placed at the east edge of the concrete pad, 15 feet from <br /> D-1 and the same distance from the northeast corner of the excavation where the <br /> hydrocarbon staining was visible. The boring was advanced to 40 feet and again, no <br /> hydrocarbons were evident in the field and none were detected in the analysis of <br /> cores from 25 and 40 feet. <br /> At the request of the San Joaquin County DHS/EHD a final boring, D-5 (Exhibit 10), <br /> was drilled at the site of the former waste oil tank at the east end of the northern <br /> warehouse. Its purpose was to collect another sample just below the tank excavation <br /> backfill for Ni and Cr analysis. No field evidence of hydrocarbons was noted during <br /> this effort. Table 3 provides the analytical results for Ni and Cr for both sampling <br /> events. <br /> TABLE 3 <br /> TTLC ANALYTICAL RESULTS FOR Ni AND Cr <br /> t <br /> WASTE OIL TANK <br /> PRELIMINARY ASSESSMENT OCTOBER 1 1992 <br /> SAMPLE LOCATIO Ni Cr <br /> T3 A East End Tank 12 10 <br /> T313 West End Tank 10 8 <br /> Analytical Method: EPA 6010 <br /> Minimum Detection Limits: Nickle - 3 mg/kg; Cr - 3 mg/kg j <br /> TTLC AND STLC ANALYTICAL RESULTS FOR Ni AND Cr +I <br /> SITE ASSESSMENT MARCH 16, 1993 <br /> SAMPLE I LOCATION Ni TTLC Ni STLC I Cr TTLCI Cr STLC <br /> D-5-10 D-5 @ 10' 12 ND 1 13 ND <br /> Analytical Method: SW-6010 <br /> Minimum Detection Limits: Ni - 0.5 mg/kg; <br /> Cr - 2.5 mg/kg <br /> REGULATORY CRITERIA <br /> TTLC STLC <br /> Ni 2000 20 <br /> Cr 2500 560 <br /> Ni and Cr are two of 17 metals listed in Title 22 of the California Code of Regulations. <br /> A waste is considered hazardous if the metal's concentration in the waste exceed <br /> certain limits listed in the regulations. Two analytical methods are specified to <br /> determine these concentrations. TTLC (Total Threshold Limit Concentration) digestion <br /> 9 <br />