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First Quarter 2001 Monitoring and Sampling Report 2 <br /> 7-Eleven Inc Store No 20632 4627 DaVinci Drive Stockton CA March 30 2001 <br /> 1 Monitoring Well Sampling and Analytical Results <br /> Quarterly groundwater samples were collected after purging at least 4 well-casing volumes of <br /> 1 groundwater from each monitoring well, unless the well was purged dry The groundwater samples were <br /> collected using disposable bailers Groundwater samples were placed in analysis-specific containers <br /> with analysis-specific preservative The samples were then sealed using Teflon septum caps, labeled <br /> with the lob identification number, the sample number, date, time, and type of laboratory analysis <br /> required The samples were stored on ice and transported with a chain-of-custody record to a state- <br /> certified laboratory for analysis Groundwater samples were analyzed for BTEX and TPH-G using <br /> Environmental Protection Agency (EPA) methods 802113/modified 8015, and for oxygenates MTBE, <br /> TBA, DIPE, ETBE, and TAME using EPA method 82608 <br /> Analytical results for the quarterly sampling event are presented in Table 1, and historical laboratory <br /> analytical results are summarized in Table 2 Highest dissolved benzene and TPH-G concentrations were <br /> reported in well MW-3 at 9 8 micrograms per liter (Ng/L) and 1,700 pg/L, respectively Dissolved MTBE <br /> was found in wells MWA (2 9 pg/L), MW-2(1,800 pg/L) and MW-5 (24 Ng/L), no detectable MTBE was <br /> found in well MW-3 Dissolved benzene, TPH-G, and MTBE concentrations are plotted on Figure 2 The <br /> laboratory analytical reports are included in Attachment 4 <br /> Prior to purging, dissolved oxygen (DO) levels were recorded in each well Dissolved oxygen levels <br /> lie ranged from about 0 4 milligrams per liter (mg/L) to 0 9 mg/L (Table 1) <br /> As mentioned in previous quarterly reports, a well search database for public water supply wells located <br /> within one mile of the site indicates that there are no public water supply wells located within 1 mile <br /> downgradient from the site <br /> Purgewater Disposal <br /> All purgewater generated during this quarterly monitoring and sampling event was stored in 55-gallon <br /> Department of Transportation (DOT)-approved drums, pending proper transport and disposal Waste <br /> disposal documentation will be forwarded once received <br /> 20632Q11 QMR <br />