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' 30 October 2003 • AGE-NC Project No 96-0232 ' Page 9 of 15 ' In addition, ground water samples were collected from municipal water wells CSA-1, CSA-2 by opening a valve from each water well outlet sample port and allowing each well pump to turn on and operate for a minimum of 15 minutes to purge the wells and then collecting the running water ' directly into the sample containers ' 3 3 LABORATORY ANALYSIS OF GROUND WATER SAMPLES r Each ground water sample was logged on a chain-of-custody form,placed in a chilled container and ' transported to a California Department of Health Services (DHS)-certified laboratory for analysis for ' • TPH-g and TPH-d by EPA Methods 5030B/8015Cm and 3510C/8015C, respectively, and • MTBE by EPA Method 8260B 34 FINDINGS ' Ground water elevation, flow direction and gradient were determined from field data collected on 15 September 2003, the contaminant impact to ground water was quantified by laboratory analysis of water samples collected on 15, 16 and 17 September 2003 3 4 1 Ground Water Elevation and Gradient The depths to groundwater were measured at between 13 14 feet(MW-18)and 17 07 feet(MW-9B) ' below the tops of the well casings on 15 September 2003, ground water elevations were calculated to be between 4 90 feet (MW-13B) and 5 68 feet (MW-2) below mean sea level (MSL) Ground water elevation at the site generally decreased an average 0 69 feet between the June and the September 2003 ground water monitoring events Ground water elevation data collected from Flag City Chevron wells MW-9 (A-C),MW-11 (A-D), IMW-13 (A-D), MW-16, MW-17, MW-18 and Three B's Truck Plaza wells MW-6, MW-9 (A-E) and MW-10 (A-F) on 15 September 2003 was depicted on cross section GC' (Figure 3), by determining the difference between ground water elevations (dh) and dividing by the difference of the screen interval midpoints (dl), the vertical gradient between adjacent screen intervals was calculated Generally,nearly flat,very slight upward and downward vertical gradients were observed I between the First Zone, Second Zone, Rocky's Upper Zone, Secondary Zone and Primary Zone screen intervals of all the above wells (Figure 3) Advanced GeoEnviromnental,Inc