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22 August 2000 . AGE-NC Project No 95-0144 Page 7 of 8 1 northeast to MW-20 The plume does not appear to extend more than 100 feet northwest to MW-13 e MTBE was detected in ground water sample MW-21B at a concentration of 25 0 µg/l and ' In MW19A and MW19B at a concentration of 1 5 µg/1 MTBE was not detected in samples from the other seven wells monitored in May 2000 The limited distribution and low concentrations of MTBE Indicate that the impact of MTBE on the site is minimal ' • TPH-g and TPH-d were detected at concentrations as high as 13,000 mg/kg and 520 mg/kg, respectively, in soil samples recovered from soil probe boring 15-6,but apparently is limited to soil shallower than 15 feet bsg, at which point a soil sample contained less than detectable concentrations of the analytes • TPH-g was detected at concentrations ranging from 6 1 mg/kg to 8,500 mg/kg in soil samples ' collected from boring 15B-9,with concentrations increasing to total depth,the vertical extent of the impacted soil was not determined ' • Lead was detected in eleven of the twelve soil samples analyzed from each of the four borings advanced at the site in May 2000 at concentrations ranging from 3 5 mg/kg to 5 9 mg/kg The detected concentrations are below the mean lead concentration in California soil l of 23 9 mg/kg and was lower than the average 22 23 mg/kg for four closest central valley soil ie samples (Background Concentrations of Trace and Major Elements in California Soils, 1996, Kearney Foundation of Soil Science) ' • The grab ground water sample recovered from soil probe boring 15B-8 contained 480 µg11 TPH-mo, 190 pg/l TPH-d, and 12,000 µg/1 lead The contaminants do not appear to be related to the known releases on the site currently under Investigation 5.0 RECOMMENDATIONS r Based upon data obtained during the second quarter of 2000 and previous sampling events, AGE ' s I ecommends • Continued quarterly monitoring of the site The next quarterly monitoring event should be ' scheduled for August 2000,concurrent with monitoring at the Van Buren site In accordance with the revised monitoring schedule, monitoring wells MW-1, MW-2, MW-4, MW-12, MW-13, MW-19A & B, MW-20A & B and MW-2IA & B will be sampled at that time ' , Implementation of the work plan submitted to the PHS-EHD for remediation at the former UST No 1 location and for feasibility testing at the former UST No 8 location upon ' regulatory agency approval i ' ' Advanced GeoEnvironmental,Inc 1 F