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S E C O R DISCUSSION Total petroleum hydrocarbons as gasoline (TPHg) were reported in two of the eleven monitoring wells ` sampled this quarter at concentrations of 440 ppb (MW-1) and 880 ppb (MW-3) Benzene was reported in two of the eleven monitoring wells at concentrations of 6 5 ppb (MW-3) to 26 ppb (MW-1) Methyl tert- butyl ether (MtBE), analyzed using EPA Method 8260B, was detected in eight of the eleven monitoring wells at concentrations ranging from 0 55 ppb (MW-9) to 130 ppb (MW-7) Tertiary butyl alcohol (TBA) was reported in one (DMW-2) of the eleven monitoring wells at a concentration of 21 ppb Di-isopropyl ether (DIPS) was reported in one well (MW-3) at 1 3 ppb 1,2-dichloroethane (1,2-DCA) was reported in six of the eleven monitoring wells at concentrations ranging from 1 2 ppb (DMW-2) to 82 ppb (MW-3) Well MW-4 was not sampled due to an insufficient amount of water in the well Well MW-2 was dry this quarter 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 northwest to north, at a gradient ranging from 0 002 to 0 004 ft/ft The direction of groundwater flow within deep wells (DMW-1 through DMW-3) was to the northwest, at a gradient of 0 002 ft/ft Groundwater elevations in shallow monitoring wells MW-1 through MW-7 increased by an average of 1 54 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 I cc Mr Marry Hartzell, Regional Water Quality Control Board -Central Valley Region (RWQCB-CVR) Ms Lori Duncan, SJCPHS Ms Madeline Scannavino, 5463 Cherokee Rd , Stockton, CA 95205 40MR02 doc