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' 20 December 2001 AGE-NC Project No 95-0128 ' Page 6 of 9 ' 2 8 SURVEYING OF MONITORING WELLS On 24 October 2001, a California state-licensed survey engineer from Baumbach & Piazza, Inc surveyed a reference point on the casing tops of wells MW-13 to MW-16 to the nearest 0 01-foot relative to the City of Stockton Bench Mark Datum BM 4 15 (elevation 10 98') The results of the monitoring well survey are contained in Tab ie 3 The surveying report(Baumbach&Piazza Job No 9797) is presented In Appendix B ' 3.0. FINDINGS ' Ground water elevations were determined by subtracting the measured depths-to-water from the surveyed casing elevations Ground water flow directions were determined by contouring the water elevations on a scaled site plan Contaminate impact to ground water samples was assessed by ' laboratory analysis The mass of hydrocarbons removed was calculated from the volume of water treated and the concentrations from laboratory analysis '• 3 1 GROUND WATER ELEVATION AND GRADIENT ' The ground water elevation on 21 October 2001 ranged from 18 90 to 21 00 feet below mean sea level(msl) The average ground water elevation during this monitoring event was approximately 2 3 5 teet lower than the average ground water elevation during the July 2001 monitoring event The depth to ground water and ground water elevation data is summarized In Table 1 The ground water table occurred within the screened intervals of the shallow screened wells The screened intervals in monitoring wells MW-1 to MW-3, MW-11B and MW-12B are currently drowned Ground water was determined to be flowing to the northeast on site and toward the east under the McDonalds property and toward the northeast and some what east off-site, under Pacific Avenue The average gradient of the ground water flow on-site was 0 004 feet/feet A ground water ridge appears off site to the north and a ground water sink Is apparent near the ground water extraction well and treatment area located at the northeast corner of the site The ground water elevations are listed in Figure 3 and contoured to denret the local ground water flow direction 3 2 ANALYTICAL RESULTS FROM GROUND WATER SAMPLES TPH-g was detected in samples MW-I,MW-4,MW-5 and VW-1 at concentrations of 51 micrograms per liter(µg/l), 8,300 ug/1, 17,000 µg/1 and 820 µIg 1, respectively Samples MW-2, MW-4,MW-5, • MWA 5 and VW-1 also contained TPH-d at concentrations of 68µg/l,4,300 gg/l,2,500 ttg/l,56 gg/1 and 180 pg/1, respectively TPH-g and TPH-d were not detected in the remaining samples Advanced CeuEnvironmental Inc