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I ' 15 March 2003 • AGE-NC Project No 98-0534 ' Page 2 of 3 ' 2 2 COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES After the depth to ground water was measured to ensure that a minimum of 80% well-volume ' recharge had been achieved, a water sample was collected from each well using a dedicated and disposable plastic bailer Immediately upon retrieval,samples were transferred Into one-liter amber bottles and three 40-m1 EPA-approved volatile organic analysis(VOA)vials containing 0 5 nil 18% hydrochloric acid as a sample preservative The samples were stored in a chilled container and the samples were logged on a chain-of-custody form The samples were later transported under chain-of- custody to Cal Tech Environmental Laboratory(CTEL), a State of California Department of Health ' Services (DHS)-certified analytical laboratory#2424 for analysis The samples were analyzed for ' • Total petroleum hydrocarbons quantified as gasoline (TPH-g) and diesel (TPH-d) In accordance with EPA Method 8015-modified for gasoline and diesel, • Benzene, toluene, ethylbenzene and total xylenes (BTEX) and methyl tertiary-butyl ether (MTBE) in accordance with EPA Method 8 02 1, and • Oxygenated compounds - di-Isopropyl ether (RIPE), ethyl tertiary-butyl ether(ETBE), M MTBE,tertiary-amyl methyl ether(TAME),tertiary butanol(TBA),ethanol,methanol, 1,2- dlbromoethane (EDB) and 1,2-dichloroethane(1,2-DCA) in accordance with EPA Method 8260B 3.0. FINDINGS Ground water elevation, flow direction and gradient were determined from field data collected on 23 January 2003 The contaminant impact to ground water was assessed from the laboratory data ' 3 1 GROUND WATER ELEVATION AND GRADIENT The relative elevation of ground water in each well was calculated by subtracting the depth to ground water from the relative casing elevation (Table 1) The average depth to ground water on 23 January 2003 was 10 feet below the tops of the well casings A ground water ridge is present in the area of the former UST with ground water flowing towards the northeast away from the former UST area, with a gradient of approximately 0 0063 feet/feet and towards the southwest away from the former UST area to 0 0052 feet/feet (see Figure 3) The ground water elevation of monitoring wells MW-4 and MW-5 appeared anomalously low and further failed to recharge after purging, ' therefore the data from these wells was not used to map the ground water elevation • Advonced GeoEnvironmental,Inc. 1