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e 1 I I J 1 18 April 2001 ' `AGE-NC Protect No 00-0769 "'• Page 3 of 5 n z _ 3 3 SURVEYING The casmg elevation of wells MW-2A, 2B, 3A and 3B were surveyed relative to City of Stockton _ Bench Mark#184 On 07 March 2001, a California state-licensed survey engineer from Baumbach & Piazza, Inc surveyed a reference point on the top of each ground water monitoring well casing' of MW-2A, -2B, -3A and-3B to the nearest 0 01-foot relative to the City of Stockton Bench Mark J Datum at 1144 feet above mean sea level(msl) On 12 April 2001, MW-1 was surveyed relative to ' MW-2B by AGE personnel The results of the monitoring well survey are contained,in Table 1 The surveying report (Baumbach & Piazza) is presented in Appendix C 4.0. FINDINGS ' Ground water elevation and flow direction were calculated from field data, hydrocarbon-impact to ground water was assessed by laboratory analysis of the ground water samples ' 4 1 ' GROUND WATER GRADIENT AND FLOW DIRECTION The relative elevation of ground water m each well was calculated by subtracting the depth to ground - water from the surveyed well head elevations Table 1 During the December 2000 monitoring event y { } g g depths to ground water ranged from 23 93 feet to 24 84 feet below the tops of the well casings Ground water elevations at the site ranged from-13 81 feet in MW-1 to --14 16 in MW-3A relative to mean sea level The ground water gradient was calculated to be 0 0004 ft/ft with a flow direction ' toward the northeast (Figure 3) Depths to ground water during the March 2001 monitoring event ranged from 23 17 feet to 24 11 feet below the tops of the well casings Ground water elevations at the site ranged from -12 92 feet in MW-3B to -13 39 in MW-3A relative to mean sea level The Iground water gradient was calculated to be 0 0011 ft/ft with a flow direction,toward the southwest ' (Figure 4) , 1 - , r = 4 2 ANALYTICAL RESULTS OF WATER SAMPLES ' TPH-g was detected in each sample analyzed during the December 2000 monitoring event at concentrations ranging from 1,500 micrograms per liter(µg/l) !n MW-2A to 190,000 µg/1 in MW-1 ' Benzene, toluene, ethylbenzene and total xylenes were detected in samples analyzed from each well The highest concentrations were detected m MW-1 at 42,000 µg/l(toluene), 33,000 gg/l(benzene), 11,000 µg/1 (total xylenes) and 2,100 µg/l (ethylbenzene) ' MTBE, TBA, DIP E, ETBE, TAME and EDB were not detected above laboratory reporting limits i• in any of the'ground water samples analyzed 1,2 - DCA was detected in samples analyzed from Advanced GeoEnvironmentai,Inc J I J J