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t a Third Quarter 2002 Monitoring and Sampling Report 7-Eleven Inc, Store#14117 2725 Country Club Boulevard Stockton, CA 3 October 23 2002 tSensitive Receptors A formal 2,000-foot sensitive receptor Investigation (to Identify all municipal and/or domestic wells in the area) is in progress for this site The Investigation will Include verification of results of an approximately 1,000-foot radius door-to-door well survey implemented in May 2001 by ETIC Engineering for the former Exxon Retail Site 7-3708 at 2705 Country Club Boulevard (Attachment 5) This survey Identified a single domestic well at 2740 Bristol Avenue, approximately 900 feet northwest of the 7-Eleven site location, and a reported (unconfirmed) domestic well at 2710 Bristol Avenue (adjacent to the 2740 property) An Environmental Data Resources Survey (EDR) report Included in the ETIC surrey reports no federal, state, or public water supply wells within one mile of the subject site Previous well search results (Fluor Daniel GTI, Onsite and Offsite Assessment Report, November 30, 1998) indicate that there are few active wells within a 2,000-foot radius of the site, and that most wells Included In the list are perforated at depths of about 100 feet bg or deeper Groundwater Monitoring Data Before monitoring, the well caps were opened to allow the water in each well to stabilize to atmospheric pressure The DTW was measured to the nearest 0 01 foot from the top of the well casing using an Interface probe A potentiometric surface map generated using the quarterly groundwater elevation data Is shown in Attachment 1, Figure 2 Based on the groundwater elevation data, the estimated groundwater flow is to the east at a gradient of about 0 004 foot per foot Quarterly groundwater elevations and historical data are presented in Tables 1 and 1A, respectively (Attachment 2) Field data sheets are included In Attachment 3 Monitoring Well Sampling and Analytical Results Before sampling, at least four well-casing volumes of water were removed from each well The groundwater samples were collected using disposable bailers Groundwater samples were placed in 40-milliliter glass vials, which were acidified with hydrochloric acid to preserve the samples The samples ' were then sealed using Teflon septum caps, labeled with the job identification number, the sample number, date, time, and type of laboratory analysis required The samples were stored on ice and transported with a chain-of-custody record to a state-certified laboratory for analysis The groundwater ' samples were analyzed for TPH-G, BTEX, and MTBE using Environmental Protection Agency (EPA) methods 8021 B/modified 8015, and oxygenates MTBE, TBA, DIPE, ETRE, and TAME using EPA method 8260B 14117023 doc