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i A groundwater elevation map for each aquifer was constructed from the data in Table 1 to illustrate • the groundwater flow direction Figure 3 shows the elevation in the 1st Riverbank aquifer The elevation of the piezometric surface in this aquifer increases to the northwest from —34 98 feet in GT-21 to —34 79 feet in GT-20, and from —34 96 feet in GT-6 to —34 65 feet in GT-13A The contours depict a trough-shaped piezometric surface, implying that groundwater is funneled from the southwest as well as from the northwest toward the axis of the trough, wluch trends toward the F east-southeast This implies a primary flow direction toward the east-southeast, which is illustrated i by the arrow in Figure 3 The hydraulic gradient averages about 0 0045 ft/ft, which is identical to t the gradient that was measured in March In the two wells that are screened in both the I"and 2„d Riverbank aquifers, the piezometric surface is approximately 0 2-0 5 feet shallower in the 2"d Riverbank than in the 1st Riverbank The elevation difference in GT-17 was 0 23 feet in March and 0 20 feet in July, and in GT-16 it was 0 51 feet in March and 0 32 feet in July (Table 1) When the piezometric surface in the 2nd Riverbank is contoured, it also has a southeast-trending trough, but there are other undulations in this surface as well Because of these undulations, the elevation is shallower in some areas but deeper in other areas than is the piezometric surface in the 1st Riverbank(e g GT-14) (Figure 4) This also suggests a more variable groundwater flow direction to the north near GT-12, east near GT-15, and southeast near GT-14 In the First Quarter 2005 Report we observed that static water levels in the 3rd Riverbank aquifer were higher by a few inches than those in the 2nd Riverbank aquifer In the second quarter, the • opposite was true, the elevation of the piezometnc surface in most wells that are screened in both aquifers was slightly lower in the 3rd Riverbank than in the 2nd Riverbank Again, the differences between wells were not uniform, so the shape of the piezometric surface in the 3rd Riverbank is different from the surface in the 2nd Riverbank but is quite similar to that in the I" Riverbank (Figure 5) Although northward groundwater flow may be occurring near GT-14, it appeals that the predominant flow direction in the 3rd Riverbank was to the southeast Thus, there is general agreement on all three maps that the main flow direction was to the southeast 3.2 Analytical Results Twenty-one groundwater samples were collected for analysis, one more than in March The damaged casing in GT-9 has been repaired, making it possible to collect a sample from this well this quarter The results are given in Table 3, and the laboratory report is ni Appendix D Diesel fuel was detected in 16 of the 21 samples, and there was very little variation in the concentrations The maximum concentration was 847 µg/l in GT-16A and the minimum was 59 5 pg/1 in GT-12B Three others were also near the 50 ppb detection limit, and the rest ranged from 100 to 350 ppb Except for the sample from GT-16A, these concentrations are all within the range that was reported in the first quarter(57 to 370 ppb) The laboratory data are contoured for each aquifer in Figures 6-8 The three maps are in good agreement, they depict an elongate plume of slightly contaminated groundwater that trends mostly north-south through the site and decreases in areal extent with depth The highest concentrations of i 3