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' TABLE 3 Historical TPH-G Concentration Summary (,uglL) San Joaquin County Human Services Building Site t Sample Date Well August 1991' April 1993 2nd Quarter 1993 3rd Quarter 1993 4th Quarter 1993 ' MW-4 520 82 96 37 JZ 140 MW-5 ND ND ND ND ND ' MW-6 ND ND ND ND ND MW-7 1,700 ND ND ND ND ' MW-8 ND 2,300 2,200 1,700 3,100 1 August 1991 data ,s trom the Phase 1I Groundwater Investigation ' 2 J = Present below detection limit As shown on Table 3, trends in TPH-G concentrations are stable in regard to location but ' variable in magnitude There appears to be no correlation between TPH-G concentrations and groundwater levels or with the rainy season 3.0 GROUNDWATER FLOW DIRECTION Groundwater elevations in each well were measured in order to evaluate the groundwater flow ' direction beneath the site The measurements were collected from all five wells within a minimum amount of time at the beginning of the field effort to ensure that the measurements reflect static water level conditions in the aquifer The groundwater elevation measurements ' (presented in Table 1) were plotted on the site map and contoured as shown on Figure 3 to show the groundwater surface morphology and the groundwater flow direction ' In general, groundwater beneath the site flows toward a groundwater trough aligned southwest- northeast across the site This flow pattern is similar to the pattern observed during all previous ' 1993 monitoring events 4.0 PROGRAM EVALUATION ' As discussed above, the 1993 monitoring program has identified only TPH-G in groundwater at monitor wells MW-4 and MW-8 Groundwater contours during the year have been very ' consistent with a low trough lying southwest to northwest through the property Essentially, groundwater converges on this trough from the northwest and southeast This consistent groundwater movement places the two monitor wells showing TPH-G sidegradient of the former ' Human Services Building tank site Srh1RPT51SJC Qrff WP 6 OVO4/W 1