ARCHIVED REPORTS XR0001328 - Laserfiche WebLink

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AWAruAM Working to Restore Nature The direction of groundwater flow on October 28, 1993 was northeast with a hydraulic gradient of Q 004 shown on Plate 3 The groundwater elevation decreased by approximately 0 22 foot since the previous monitoring event Groundwater samples were analyzed for TPHg and BTEX using EPA Methods 5030 and 8020 and DHS LUFT methods prescribed by the State of California Samples were also analyzed for HVOCs using EPA Methods 5030/601, and the sample from well MW-2 was analyzed for TOG using Standard Methods (SM) 5520C and 5520F These samples were analyzed at Columbia Analytical Services, Inc in San Jose, California (Hazardous Waste Testing Laboratory Certificate 1426) The results of analyses are summarized in Tables 2 and 3 Copies of the laboratory analysis reports are in the appendix. Results of analyses indicated dissolved gasoline hydrocarbons were detected in samples from th �W3.000 Concentrations of TPHg ranged from 17,000 (well MW-2) parts per billion (ppwell MW-6)ppb, and benzene concentrations ranged from 3,100 (well MW- 1 7) ppb to 15,000 (well MW-6) ppb 1,2-Dichloroethane was detected in groundwater samples from the wells at concentrations ranging from 0.7 ppb to 690 ppb, 1,2- dichloropropane was detected in wells MW-1, MW-2, MW-4, MW-5, and MW-7 at concentrations ranging from 0 5 ppb to 12 ppb TOG was detected in well MW-2 at concentrations of 11 ppb using SM 5520C and 5520F, respectively (Table 3) Concentrations of TPHg and benzene are shown on Plate 2 WORK IN PROGRESS RESNA is currently preparing a Problem Assessment Report /CONCLUSIONS AND RECOMMENDATIONS Residual hydrocarbons were detected in soil samples collected upgradlent from the site at depths of 20 5 feet and 34 5 feet The direction of groundwater flow has ranged from the northeast to the southeast. Dissolved gasoline hydrocarbons and halogenated volatile organic compounds were detected in samples from the seven wells. TOG was detected in sample collected from MW-2 Based on relatively high concentrations of dissolved hydrocarbons in wells MW-6 and MW-7 (hydraulically upgradlent from the ARCO service station), it a ears a h drocarbon source exist adient We recommend continued quarterly evaluation of groundwater beneath the site, including analyzing water samples for HVOCs, TPHg, and BTEX We also recommend water sample from wells MW-2 and MW- 6 be analyzed for TOG and HVOC, to verify that these previously detected hydrocarbons are from an offsite source y. 1130ccar/31009-9 4