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_ r i r r 5 t i s ' 23 May 2001 AGE-NC Project No b5-0144 t Page 6 of 8 ' at concentrations as high as 2,100 mg/kg and 1,100 mg/kg, respectively Toluene was detected in three of the stockpile samples at concentrations ranging from 0 007 mg/kg to 0 018 mg/kg Ethylbenzene and total xylenes were detected in two of the four stockpile samples at concentrations ' as high as 0 50 mg/kg and 1 4 mg/kg, respectively , One sample was collected from each wall and from the floor of the excavation Toluene was detected in the sample collected from the south wall at a concentration of 0 016 mg/kg TPH-d was detected in the floor sample at a concentration of 1 1 mg/kg No other petroleum hydrocarbon contamination ; was detected in the five soil samples collected from the excavation 1 Samples collected from the soil stockpile and excavation walls and floor did not contain dectectable concentrations of fuel additives or volatile halocarbons Concentrations of CAM 17 metals were well below the total threshold limit concentrations (TTLCs) for each metal and were generally within the, t' range of normal background concentrations for California soils Soil sample locations are illustrated ' in Figure 5 Analytical results of the excavation soil samples are summarized in Tables 4 and 5 Laboratory analytical reports (MAI Lab IDs 63682 through 63690) are included in Appendix D 3 \ li ' 4.0. SUMMARY/CONCLUSIONS r 1 Based upon data collected during the ground water monitoring event, AGE concludes f • Ground water elevation decreased approximately 0 61 feet at the site since the previous ' ground water monitoring event Ground water remained above the screened interval in eight of the shallow wells sampled during the current quarter Ground water elevations in wells completed beneath the clay layer (approximately 35-45 feet bsg) were lower than in wells completed within first ground water w • Petroleum hydrocarbons were detected in four of the ten wells sampled during the February 2001 monitoring event Concentrations of TPH-g have decreased slightly in monitoring wells MW-21A and MW-21B since the November 2000-monitoring event Concentrations of TPH-d have decreased slightly in monitoring wells MW-2, MW-4, MW-13, MW-19A, , MW-19B and MW-21B and slightly increased in monitoring wells MW-20A and MW-21A ' since the last quarterly monitoring event TPH-mo has increased significantly m monitoring well MW-21A, the only well that contained detectable concentrations of the analyte during 1 the February 2001 monitoring event • TPH-g was detected in wells MW-21A and MW-21B located within the former UST No 8 pit The extent of ground water impacted by TPH-g ,is limited to the area immediately surrounding the former UST No 8 , Advanced GeoEnvironmenta4 Inc