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f S 06 1 E C O R dibromide (EDB), and ethyl tert butyl ether (ETBE)were not detected this quarter Chemical concentrations were generally consistent with historical data Wells MW-1, MW-2, MW-4, SVE-1, EW-1, and EW-6 were • not sampled this quarter because they are hooked up to a remedial system These wells will be sampled in all future quarterly sampling events Well MW-8 was not sampled due to a car broken down on top of the well, the car's owner was not in the vicinity Groundwater elevations across the site increased by an average of 0 63 ft Groundwater flow for the shallow water-bearing zone was to the northeast at an approximate gradient of 0 005 ftlft, and for the deep water bearing zone was to the northeast at an approximate gradient of 0 007 ft/ft, consistent with historical data Sampling dates were coordinated with the Tosco station 4409 located across the street from Arco 4932 Attachment C contains the groundwater elevations and analytical data for Tosco Station 4409 (Gettler- Ryan) 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 • Figure 1 - Groundwater Elevation Contour Map—Shallow Water Bearing Zone • Figure 2—Groundwater Elevation Contour Map—Deep Water Bearing Zane • Figure 3—Groundwater Chemical Concentration Map • Figure 4 —MtBE Isoconcentration Contour Map—Shallow Water Bearing Zone Figure 5—MtBE Isoconcentration Contour Map-Deep Water Bearing Zone • Attachment A- f=ield and Laboratory Procedures • Attachment B - Certified Laboratory Analytical Reports, Chain-of-Custody Documentation, and Field Data Sheets Attachment C—Former Tosca (Unocal) Service Station#4409 Groundwater Monitoring and Sampling Report(Gettler-Ryan) cc Mr Marty Hartzell, Regional Water Quality Control Board -Central Valley Region (RWQCB-CVR) Ms Lora Duncan, SJCPHS , Vern Elrath, URS Corporation I WRM49321QMRs1200312QMR03 doc -3-