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' 20 October 2004 <br /> • AGE-NC Project No 98-0497 <br /> ' Page 2 of 4 <br /> ' 2 2 GROUND WATER SAMPLE COLLECTION <br /> Prior to the collection of ground water samples, the depth to ground water was re-measured in each <br />' well to ensure that a minimum of 80% of the initial water volume had recharged Water samples <br /> were then collected from each well using a clean,disposable plastic bailer The water was transferred <br /> into one 1-liter amber bottle and three chilled 40-m1 volatile organic analysis(VOA)vials containing <br /> 0 5 ml hydrochloric acid(18%)as a sample preservative After collection,the samples were labeled <br /> and placed in a chilled container for transportation under chain of custody to Cal Tech <br /> Environmental Laboratones(CTEL),a Department ofHealth Services-certified analytical laboratory <br /> Each sample was analyzed for <br /> • Total petroleum hydrocarbons as gasoline and diesel(TPH-g and TPH-d)in accordance with <br />' EPA Method 8015M, and <br /> • Benzene,toluene,ethylbenzene and xylenes(BTEX)and methyl tertiary-butyl ether(MTBE) <br /> in accordance with EPA Method 8021 B <br /> 10 3.0. FINDINGS <br />' Ground water elevation and flow direction were inferred from field data Hydrocarbon-impact to <br /> ground water was assessed by laboratory analysis of the ground water samples <br />' 3 1 GROUND WATER ELEVATION AND GRADIENT <br /> Ground water elevations were determined by subtracting the measured depths to water from the <br /> surveyed casing elevations The average ground water elevation on 20 May 2004 was 40 74 feet <br /> below mean sea level (MSL)and the average depth to water was 65 7 feet below the casing tops The <br />' average ground water elevation in the wells decreased by approximately 0 94 feet between the March <br /> and May monitoring events Groundwater was within the screened interval of each monitoring well <br /> e <br />' The water table flow direction at the former UST location was determined to be east-northeast under <br /> an average gradient of approximately 0 002 ft/ft Figure 3 illustrates the contoured ground water <br /> elevations as measured on 20 May 2004 <br /> • <br />' Advanced GeoEnviro n mental <br /> 1 <br />