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■� J First Quarter 2003 Monitoring Report Quik Stop Market No 121 Page 3 MW-4, screened from 33 to 43 feet in the A-aquifer, was reported to contain 7 8 ug/L MTBE, and no detectable TPHg or BTEX compounds Monitoring well MW-5, located on the southwest side of the site, was reported to be free of detectable TPHg and BTEX compounds but contained 16 ug/L MTBE and 5 2 TBA All three deep wells (B-aquifer), wells MW-6, MW-9 and MW-10, screened from 65 to 75 feet within the B-aquifer, were reported to be free of detectable TPHg and BTEX compounds Monitoring wells MW-9 and MW-10 were also reported to be free of detectable fuel oxygenate compounds Monitoring well MW-6 was reported to have detectable MTBE, at 1 7 ug/L No other detectable compounds were reported in the three B-aquifer wells The results of the groundwater analysis are summarized in Table 2 Graphs for wells MW-3, MW-4 and RW-1, summarizing TPHG and MTBE concentrations over time, are presented The analytical reports from STL San Francisco and chain-of-custody documents are attached in Appendix B Discussion Groundwater measurements taken in the ten shallow A-aquifer wells on January 9, 2003, indicated the depth-to-groundwater ranged from approximately 18 40 to 19 91 feet below the top of the well casings The water level in monitoring well MW-4 was measured at 18 72 feet below the top of the well casing The water table in the shallow A-aquifer has risen approximately 2 to 4 feet during the last three months The groundwater table at the site is essentially flat, with a very slight gradient of 0 006 feet per foot to the northeast around well MW-5, 0 006 feet per foot to the northwest at MW-7, and a slight gradient of 0 005 feet per foot to the north on the north side of the site (Figure 4) Groundwater measurements taken in the three B-aquifer wells indicated the depth-to- groundwater ranged from approximately 18 84 to 19 91 feet below the top of the well casings The water table in the B-aquifer has risen approximately 6 5 feet during the last three months A groundwater gradient map for the B-aquifer was created and indicates a gradient of 0 001 feet per foot to the northwest (Figure 5) CCI collected background dissolved oxygen (D O ) readings on January 9, 2003 The D O readings at that time ranged from 3 75 ug/L in MW-5 to 9 25 ug/L in MW-4 Since the System was activated in early August, the D O levels have increased significantly in nearly all the wells The D O levels are summarized in Table 3 Based on the groundwater data obtained during the quarter, it appears the MTBE and TPHg concentrations have begun to decrease significantly in some of the site wells The MTBE concentrations reported in well RW-1 have dropped from 160,000 ug/L on August 16, 2002 to •