ARCHIVED REPORTS XR0000938 - Laserfiche WebLink

Home Browse Search

ji '14 August 2002 . AGE-NC Project No. 98=0440 IPage 3 of ` 3.2. ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in the water sample collected from monitoring well MW5 at a concentration of 240 µg11.'TPH-d was detected in the water samples collected from monitoring wells MW_ 2, MW3 and MWS at concentrations of 57.gg/l, 290 µg11 and 230 µg/l, respectively. Benzene, toluene and xylenes were detected in the Water.sample collected from well MW5' at' concentrations of 1.7 gg/l, 2.5 gg/l and 9.1 gill,respectively. No other analytes were-detected at or above laboratory reporting limits iIi the water samples•collected. Current and previous_analytical results are summarized on Table 2.The laboratory report(MAI Lab ID No.0206442-061 through 02064427006),QA/QC report and chain-of-custody form are included in Appendix B. 4.0. SUMMARY AND CONCLUSIONS Based on the data collected during this monitoring period, AGE concludes: • On 26 June 2002, the ground water at the site was inferred to be flowing toward the north-northwest under an average gradient of 0.009'feet/feet across the area monitored. • The highest concentration of dissolved hydrocarbons quantified as TPH-g, TPH-d and BTEX compounds extends northeast from USTs No. 4 and 5. Dissolved hydrocarbons were encountered in the down-gradient ;direction from the ,former USTs_ in .samples. from monitoring wells MW2, MW3 and.MW5. Dissolved hydrocarbon concentrations were non-detectable in samples from wells MW T, MW4' and MW6. A map showing the, approximate extent of dissolved TPH-g,and benzene is presented in-Figure 5. The-concentration,of benzene detected in the water sample collected from well MW5 is just above the State of California maximum contaminant level(MCL)of 1.0 µg11 for benzene in drinking water. • The lateral extent of petroleum hydrocarbon-impacted ground water,has.not been defined toward the north and northeast beyond MW5.,The hydrocarbon plume is fairly well defined to,the south, east, west and northwest. Advanced GeoEnvironmental,Inc.