ARCHIVED REPORTS_REMEDIAL INVESTIGATION REPORT 2000

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07 February 2000 AGE-NC Project No. 95-0144 Page 2 of 4 2.2. COLLECTION OF GROUND WATER SAMPLES The depth to water was remeasured immediately following purging in each well to determine recharge.A minimum of 80 percent recharge was observed in each well,except MW-19A,MW-20B and MW-21B immediately after purging. Water samples were collected from each purged well using new disposable bailers. Samples were transferred into 40-m1 EPA-approved VOA vials containing 0.5 ml 18% hydrochloric acid as a sample preservative and into 1-liter amber bottles without preservative. The samples were labeled, stored on ice and transported under chain-of-custody to McCampbell Analytical, Inc. (MAI), a California Department of Health Services (DHS)-certified analytical laboratory. Each sample was analyzed for: • Total petroleum hydrocarbons quantified as gasoline(TPH-g), diesel (TPH-d) and motor oil (TPH-mo) in accordance with EPA Methods 5030/8015m; and • Volatile aromatic hydrocarbons-benzene, toluene, ethylbenzene and total xylenes (BTEX) and methyl tertiary-butyl ether(MTBE) in accordance with EPA Method 8020/602. Samples collected from wells MW-19A&B,MW-20A&B and MW-21A&B were also analyzed for: • Volatile organic compounds and fuel oxygenates; di-isopropyl (DIPE),1 ether p ( IPE), ethyl tertiary- butyl ether(ETBE),MTBE,tertiary-amyl methyl ether(TAME) and tertiary butanol (TBA) in accordance with EPA Method 8260 modified. 3.0. FINDINGS Ground water elevation and flow direction were calculated from field data; hydrocarbon-impact to ground water was inferred from laboratory analysis of the ground water samples. 3.1. RELATIVE GROUND WATER ELEVATION AND GRADIENT The elevation of ground water in each well was calculated by subtracting the depth to water from the surveyed casing elevation(Table 1). Between August and November 1999, ground water elevation decreased an average of 1.01 feet in monitoring wells MW-19B, MW-20B and MW-21B, screened below a clay layer. Ground water elevation decreased an average of 1.25 feet in the remaining wells. The approximate hydraulic gradient for the November 1999 monitoring event was calculated to be 0.003 ft/ft with a northerly flow direction. Ground water elevation contours derived from data collected on 08 November 1999 are depicted in Figure 3. Ground water was between approximately 0.1 and 3.5 feet above the screened interval in monitoring wells MW-1,MW-2,MW4 and MW-13. Advanced GeoEnvironmental,Inc.