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Second Quarter 2000 Monitoring and Sampling Report and Well Search 2 7-Eleven Inc Store#17647 1048 West Yosemite Avenue Manteca CA Ma 15 2000 Monitoring Well Sampling and Analytical Results On April 7, 2000, groundwater samples were collected from the three monitoring wells Dissolved oxygen (DO)concentrations were measured in the three wells prior to sampling The groundwater samples were collected using disposable bailers Groundwater samples were placed in analysis-specific containers with analysis-specific preservative 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 Groundwater samples were analyzed for BTEX and TPH-G using EPA methods 8021/modified 8015 , for ' the oxygenates MTBE, TBA, DIPE, ETBE, and TAME using EPA method 8260 Dissolved oxygen data taken from three monitoring wells indicated a slight increase in oxygen levels for the ' two upgradient wells (MW-1 and MW-2) and a slight decrease in the oxygen level for downgradient well, MW-3 Dissolved oxygen readings taken ranged from 0 5 mg/L in MW-3 to 2 1 mg/L. in MW-2 (Table 1) ' Laboratory analytical results for groundwater samples collected on April 7, 2000 and historical results are summarized in Table 1 Dissolved benzene and TPH-G concentrations were not detected above reporting limits in any of the wells sampled Dissolved MTBE concentrations were only detected in downgradient ' well, MW-3 at 26 pg/L The other oxygenates were not reported above detection limits in any of the wells sampled during the second quarter 2000 All gasoline constituents analyzed remained below detection limits in groundwater samples from the two upgradient wells (MW-1 and MW-2) Benzene, MTBE and TBA concentrations in downgradient well, MW-3, declined between 53 and 76 percent since the first quarter 2000 The dissolved hydrocarbon plume appears restricted to a limited area between the former ' underground storage tanks and MW-3 Low and declining dissolved hydrocarbon concentrations with declining dissolved oxygen levels (MW-3) indicate that the natural attenuation/biodegradation is occurring The laboratory analytical reports for the groundwater samples are included in Attachment 4 ' Well Search I t IT Corporation performed a well search using multiple sources of information to assemble a database for wells located within one mile of the site The database includes well ownership, depth of sanitary seal,well type, length of screen, location, operation pumping rate, status, and any available testing information The ' database for this site indicates there are approximately 14 wells within a one mile radius of the site The nearest wells are approximately 993 feet to the north (crossgradlent) of the site The database indicates that there are two downgradient wells located approximately 4,956 feet southwest of the site Database ' information, a Well Data Table, and'Well Survey Map are included in Attachment 5 Purge Water Transportation and Disposal All purge water generated during this quarterly monitoring and sampling event was stored in 55-gallon ' Department of Transportation (DOT)-approved drums pending characterization and proper disposal Approximately 37 gallons of purged water generated during this sampling event will be removed from the site during the next quarter by Belshire Environmental Services, Inc and transported to a licensed treatment and disposarl facility) Waste disposaldocumentationwill be forwarded once received, E r l 217%q2 rpt