ARCHIVED REPORTS XR0003325 - Laserfiche WebLink

Home Browse Search

Second Quarter 1999 Mondonng and Sampling Report/Request for Closure 2 7-Eleven !nc -Store#20632 4627 Davina Drive Stockton CA JUIV 1 1999 Monitoring Well Sampling and Analytical Results On May 21, 1999,groundwater samples were collected from four wells (MW-1, MW-2, MW-3 and MW-5 ' (well MW-4 was abandoned during UST upgrades in 1998)) Before sampling, at least 4 well casing volumes of groundwater was removed from each monitoring well unless the well was purged dry 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 fob idenbficabon number,the sample number, date, time, and type of t laboratory analysis required The samples were stored on ice and transported under a chain-of-custody record to a state-certified laboratory Groundwater samples were analyzed for BTEX and TPH-G using Environmental Protection Agency (EPA) methods 8020/modified 8015, and for oxygenates MTBE, TBA, ' DIPE, ETBE, and TAME using EPA method 8260 Laboratory analytical results for groundwater samples collected on May 21, 1999, are presented in Table 1 The laboratory analytical reports for the groundwater samples are included in Attachment 4 Histoncal data is included in Table 2 Dissolved benzene levels ranged up to 24 2 micrograms per liter (pg/L), and dissolved TPH-G levels ranged up to 1,180 pg/L Dissolved MTBE concentrations ranged up to 5,340 pg/L ' Highest dissolved benzene concentrations were found directly downgradient from the underground storage tank area, highest TPH-G and MTBE levels were found in downgradient/crossgradlent well MW-2 Observed concentrations and hydrocarbon distribution are similar to previous quarters There are no private or public municipal or domestic wells within 2,000 feet of the site Dissolved oxygen levels in the affected areas indicate localized depletion, through intrinsic biodegradation ' 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 Waste disposal documentation will be forwarded once received 1 �