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r4 5j S E C 0 R 1) Methyl tert-butyl ether (MtBE), analyzed using EPA Method 82606, was detected in nine of the eleven monitoring wells at concentrations ranging from 0 61 ppb (MW-9) to 170 ppb (DMW-3) Tertiary butyl alcohol (TBA) was reported in one (MW-3) of the eleven monitoring wells at a concentration of 24 ppb DI-isopropyl ether (DIPE) was reported 1n one well (MW-3) at 1 4 ppb 1,2-dichloroethane (1,2-DCA) was reported in seven of the eleven monitoring wells at concentrations ranging from 0 70 ppb (MW-5) to 34 ppb (MW-3) Wells MW-2 and MW-4 were not sampled due to an insufficient amount of water in the wells Chemical concentrations were generally consistent with historical data Additionally, domestic well WSW and well DW-2 were sampled for TPHg, BTEX, MtBE, and other fuel oxygenates/additives, all of which were reported as non-detectable above the method reporting limits The direction of groundwater flow within shallow wells (MW-1 through MW-10) was southeast, at a gradient of 0 004 ft/ft The direction of groundwater flow within deep wells (DMW-1 through DMW-3) was to the south-southeast, at a gradient of 0 001 ft/ft Groundwater elevations in shallow monitoring wells MW-1 through MW-10 decreased by an average of 1 03 ft SECOR is performing granulated activated carbon treatment on well DW-1 Influent and effluent water samples are taken monthly and reported under separate cover in monthly performance summaries DW- 2 and the onsite water supply well (WSW) are Incorporated into the quarterly monitoring and reporting Analytical data from DW-2 is included In Tables 4 and 5 Certified laboratory analytical data are included In Attachment B This report presents our understanding of existing conditions at the subject site The conclusions contained herein are based on the analytical results, and professional judgment in accordance with current standards of professional practice, no other warranty is expressed or implied SECOR assumes no responsibility for exploratory borings or data reported by other consultants or contractors . ATTACHMENTS. • Table 1 —Groundwater Elevation and Analytical Data • Table 2—Fuel Oxygenates Analytical Data • Table 3 - Groundwater Gradient Data • Table 4— Domestic Well Analytical Data • Table 5—Domestic Well Fuel Oxygenates and Nitrate/Nitrite Analytical Data • Figure 1 —Shallow Groundwater Elevation Contour Map • Figure 2— Deep Groundwater Elevation Contour Map • Figure 3 - Groundwater Chemical Concentration Map • Attachment A- Field and Laboratory Procedures • Attachment B - Certified Laboratory Analytical Reports, Chain-of-Custody Documentation, and Field Data Sheets cc Mr Marty Hartzell, Regional Water Quality Control Board - Central Valley Region (RWQCB-CVR) Ms Lori Duncan, SJCPHS Ms Madeline Scannavino, 5463 Cherokee Rd , Stockton, CA 95205 1\AFi00105951QMRs12003\1QMR03 doo