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29 January 1998 AGE-NC Project No 95-0184 ' Page 2 of 4 ' preservative The samples were labeled, placed In a chilled container and transported under chain-of- custody to McCampbell Analytical, Inc (MAI) In Pacheco, California The samples were analyzed in accordance with EPA Method 5030 and 8015m for total petroleum hydrocarbons quantified as gasoline (TPI -g), in accordance with EPA Method 602/8020 for volatile aromatics hydrocarbons (benzene,toluene,ethylbenzene and xylenes, BTE&X)with methyl tertiary-butyl ether(MTBE)and in accordance with EPA Method 624/8260 for volatile organic compounds and oxygenated volatile organic compounds The sample from MW-4 was also analyzed in accordance with EPA Method 8015m for total petroleum hydrocarbons quantified as diesel (TPH-d) ' 23- CASING ELEVATION SURVEY ' On 22 December 1997,the elevation of each monitoring well casing was surveyed relative to a City of Stockton bench mark Surveying was performed by Mr Terry Piazza of Baumback&Piazza, Inc Revised casing elevations were used to recalculate all ground water elevations The survey sheet is included in Appendix C 3.0. FINDINGS - 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT The average depth to ground water at the site was 39 71 feet below the well casing tops during the October 1997 monitoring event Ground water elevation decreased an average of 1 25 feet between July and October 1997 Ground water was approximately 15 feet above the screened interval in monitoring wells MW-1, MW-2 and MW-3 Ground water elevations In these wells did not correspond to elevations measured In the remaining wells at the site A confining layer may be present, preventing equilibrium of ground water elevation between the first encountered ground water and deeper ground v ater' at the site Vapor well VW-5 was installed at an angle of approximately 15° from vertical For these reasons, ground water elevation measurements from MW-1, MW-2, MW-3 and VW-5 were not used for calculating the ground water flow direction The revised casing elevations were used to calculate the ground water gradient and flow directions for the July and October 1997 monitoring events The average ground water gradient and flow I direction in July 1997 were calculated to be approximately 0 009 ft/ft directed N 63° E (Figure 3) The ground water gradient and flow direction in October 1997 were calculated to be approximately 0 02 ft/fl directed S 50° E toward the north end of the site and approximately 0 006 ft/ft directed S 70° E at the south end of the site (Figure 4) Measurable free product was not encountered at the site during the July or October 1997 monitoring events, however, a-thin film of product was noted in well VW-513 during the October 1997 monitoring event Advanced CeoEmiron mental,Inc