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Unocal Service Station No 0187 <br /> September 21, 1994 <br /> Stockgile Sample <br /> TPH-Gasoline was detected in the stockpile sample at a concentration of 270 <br /> ppm Benzene was detected in this sample at a concentration of 0 24 ppm. The <br /> total lead concentration in this sample was 6 7 ppm These data are summarized <br /> in Table 3 <br /> Groundwater Sample <br /> No fish were killed in the bioassay or the control group after 96 hours at 100 <br /> ppm or at 750 ppm Two fish from the duplicate group died after 48 hours at a <br /> concentration of 100 ppm, but none from the duplicate group died after 96 hours <br /> at 750 ppm <br /> DISCUSSION <br /> Vertical and horizontal delineation of hydrocarbon impact to soil beneath the <br /> subject site is incomplete at this time TPH-Gasoline or BTEX compounds were <br /> detected in a soil sample from well boring U-2 (at 45 5 feet bgs), and in all soil <br /> samples collected from well boring U-3 and exploratory borings U-J through U-M <br /> Hydrocarbon-impacted soil appears to extend vertically to groundwater, and <br /> laterally offsite to the south and east Hydrocarbon impact to groundwater <br /> beneath the subject site will be assessed after receipt of quarterly monitoring and <br /> sampling report from MPDS <br /> As discussed in our letter to SJCEHD dated August 3, 1994, data from this and <br /> previous subsurface investigations at the subject site indicate that soils beneath <br /> either of the former waste oil USTs do not contain the metals Cd, Cr, Pb, Ni, and <br /> zinc (Zn) in concentrations above their respective STLCs In our opinion, no <br /> further investigation of metals in the soil beneath this site is warranted Mr <br /> Collins of the SJCEHD has already concurred with this opinion <br /> Repan No 4827 7036 7 <br /> GeoStrategies Inc. <br />