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i 09 January 1998 • AGE-NC Project No 96-0235 ' Page 4 of 6 F during grading operations at the site Approximately 0 90 feet of well casing was removed On 18 ' December 1997, the elevation of each monitoring well casings was surveyed relative to a City of Stockton bench mark Surveying was performed by Mr Terry Piazza of Baumback-Piazza The survey sheet is included in Appendix C Revised casing'elevations were used to recalculate all ground water elevations, ground water elevations for MW-2 prior to May 1997 reflect the recalculated casing elevation prior to alteration _ 4.0. FINDINGS , 1 41 GROUNDWATER GRADIENT AND FLOW DIRECTION ` ' The elevation of ground water in each well was calculated by subtracting the ground water depth from the surveyed casing elevations Depths to ground water ranged from 22 14 feet to 23 55 feet below the well casings Ground water elevations at the site ranged from -15 43 feet in MW-4 to ' - 16 26 feet in MW-1 ' The revised well casing elevations were used to recalculate the ground water flow direction for 27 May 1997 as well as the current data The flow direction was complex for both monitoring events, as a trough of lower elevation ground water cuts diagonally, northwest/southeast across the property ' as indicated by the low ground water elevation in MW-I'and MW-2, causing all flow directions on the property to be toward MW-1 and MW-2 The trough dipped toward the northwest during the May 1997 monitoring event and toward the southeast during the November 1997 monitoring event ' The contoured ground water flow elevations for the May and November 1997 �giound water monitoring events are depicted in Figure's 4 and 5 The revised casing elevations did not significantly alter the observed ground water gradient for the May 1997 monitoring event ' - The ground water gradient and flow direction for all monitoring events were recalculated using MW- 1, MW-2 and MW-3 with the revised casing elevations All ground water elevations and gradients ' are summarized on Table 4 The calculated gradient direction for the March 1995 monitoring event does not match those calculated during the remaining monitorings The data for MW-3 may be in ' error, as the change in ground water elevation does not appear to match that of MW-Vaud MW-2 If an error of one foot is considered,,the gradient and flow direction more closely match those measured during the remaining monitoring events 42 ANALYTICAL RESULTS OF WATER SAMPLES ' TPH-g was detected in MW-1, MW-2 and MW-3 at concentrations of 820 parts per billion (ppb, measured as micrograms per liter), 18,000 ppb and 53 ppb, respectively Benzene was detected in ' Advanced GeoEnN ironmentai,line r