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■1 M) Quik Stop Market No 121 CCI Project No 12118-2 Page 4 One of the three deep (B-aquifer) wells ( MW-6, MW-9 and MW-10) screened from 65 to 75 feet within the B-aquifer, was reported to have detectable MTBE Monitoring well MW-6 was reported to have 21 ug/L MTBE No other detectable compounds were reported in the three B- aquifer wells The results of the groundwater analysis are summarized in Table 2 The analytical reports from ChromaLab and chain-of-custody documents are attached in Appendix D Discussion Based on the groundwater data obtained during the quarterly sample round, it appears the groundwater continues to be impacted with petroleum hydrocarbons, mainly in the vicinity of Quik Stop Market's fuel tanks located on the southeast side of the site, near monitoring wells MW-3, MW-4 and RW-1 (Figures 2) Groundwater samples collected from perimeter wells MW-2, MW-11, MW-7 and MW-12 were reported to be free of detectable TPHg/BTEX and MTBE compounds As previously indicated, monitoring well MW-8 was found to be dry this quarter Groundwater in the vicinity of monitoring wells MW-3, MW-4 and RW-1 were reported to have the highest contaminant concentrations of MTBE at the subject site It appears MTBE has migrated to a lower portion of the A-aquifer, at a depth of 33 to 43 feet, as detected in the water sample collected at MW-4 and continues to be detected in low concentrations in B-aquifer well MW-6 The other two B-aquifer wells, MW-9 and MW-10, were reported to be free of detectable petroleum compounds Groundwater measurements taken in nine of the shallow A-aquifer wells on October 4, 2001 indicated the depth-to-groundwater ranged from approximately 2146 to 22 76 feet below the top of the well casings The water level in monitoring well MW-4 (screened in the A-aquifer from 33 to 43 feet) was measured at 21 80 feet below the top of the well casing The water table in the shallow A-aquifer has risen slightly since the second quarter sample round Groundwater contours in the A-aquifer monitoring wells indicate the groundwater gradient to range from 0 003 to 0 006 feet per foot to the north-northeast (Figure 3) A groundwater gradient map for the B- aquifer was created and indicates a gradient of 0 002 feet per foot to the northwest (Figure 4) Quik Stop Markets, Inc continues to conduct 8-hour dual-phase treatment events at the site on a monthly basis, using a mobil treatment system (MTS) operated by TRC of Concord, California, until a permanent treatment system can be installed at the site During this quarter, three additional MTS events (for a total of 7 ) were conducted at the site in August, September and October, 2001 A review of the vapor concentration data from the last 7 MTS events shows the vapor concentrations to be decreasing significantly in the extraction wells by the end of each • 8-hour event This trend appears to be confirmed in the groundwater samples, since the MTBE concentrations have decreased in the 3 wells with the highest concentrations (RW-1, MW-3