ARCHIVED REPORTS XR0000937 - Laserfiche WebLink

Home Browse Search

L a 30 October 2002 AGE-NC Project No. 98-0440 Page 3 of 4 3.2. ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in the water sample collected from monitoring wells MW5 and MW6 at concentrations of 570 4g/1 and 350 pg/l,respectively.TPH-d was detected in the same water samples at concentrations of 520 µg/l and 450 gg/l, respectively. Benzene, toluene and xylenes were detected in the water sample collected from well MW5 at concentrations of 1.4 gg/l, 2.2 4g/1 and 19 }tg/l, respectively. Toluene was detected in the water sample collected from well MW6 at a concentration of 3.3 pIg/l and ethylbenzene was detected in the sample from well MW2 at a concentration of 2.2 gg/I. No other analytes were detected at or above laboratory reporting limits in the water samples collected from the monitoring wells. No analytes were detected at or above laboratory reporting limits in the water sample collected from the domestic well located at the site (DW5157). Current and previous analytical results are summarized on Table 2. The laboratory report(MAI Lab ID No. 0209417-001 through 0209417-007),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 25 September 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, MW5 and MW6. Dissolved hydrocarbon concentrations remained non-detectable in samples from wells MWI, MW3 and MW4. 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 was just above the State of California maximum contaminant level(MCL)of 1.0µg/l for benzene in drinking water. • No analytes were detected at or above laboratory reporting limits in the water sample collected from the domestic well located at the site (DW5157). Advanced GeoEnvironmental,Inc.