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1 <br /> FkVt Cusrter 19N lAonitorinp snit Sampling RepoWR&West for Closure 2 <br /> The Southland -Sims#20632,4627 DrAW DrW Stockton CA July 9 1998 <br /> Monitoring Well Sampling and Analytical Results <br />' On June 15 1998groundwater samples were collected from the four monitor wells -1 through <br /> MW-4) Before sampling,at least 4 well-casing volumes of groundwater was removed from each <br /> monitoring well unless the well was purged dry The groundwater samples were collected using disposable <br /> bailers Groundwater samples were placed In analysis-specific containers with analysâ–şs-specific <br />' preservative. The samples were then sealed using Teflon septum caps, labeled with the job identification <br /> number,the sample number,date,time, and type of laboratory analysis required The samples were <br /> stored on ice and transported under a chain-of-custody record to state-certified Core Analytical Laboratory, <br />' in Anaheim,California Groundwater samples were analyzed for BTEX and TPH-G using Environmental <br /> Protection Agency(EPA) methods 80201modified 8015,and for oxygenates MTBE,TBA, DIPS, ETBE, and <br /> TAME using EPA method 8260 <br /> Laboratory analytical results for groundwater samples collected on June 15, 1998 are presented in Table 1, <br /> and historical results are summarized in Table 1A Dissolved benzene was detected in one well,MW-4, at <br />' 700 micrograms per Inter(pg/L) Highest dissolved TPH-G and MTBE concentrations were reported in well <br /> MW-4 at 22,000 pg/L and 17,000 pg/L,respectively Since October of 1997, BTEX concentrations in the <br /> downgradient well(MW 2) remained below detection limits while hydrocarbons In the upgradient well (MW- <br /> 1) <br /> MW1) have dropped to non-detectable levels,and in cross gradient well MW-3, benzene,TPH-G and MTBE <br /> concentrations have deckned below method detection limits Overall, reduced hydrocarbon concentrations <br /> found in monitoring wells at the plume periphery documents that the hydrocarbon plume is stable and In a <br /> general state of attenuation <br />' Underground storage tank upgrades will occur later on in the year at this site with active source area <br /> remediation occurring while the tank pit is open Seasonal recharge due to winter rains has apparently <br /> increased the amount of dissolved oxygen in the affected areas,which will lead to a corresponding Increase <br />' in intrinsic bioremediation <br /> The laboratory analytical reports for the groundwater samples are included in Attachment 4 <br />' Purge Water Transportation and Disposal <br />' Ail purge water generated during this quarterly monitoring and sampling event was stored in 55-gallon <br /> Department of Transportation (DOT)-approved drums pending characterization and proper disposal <br /> Approximately 21 gallons of purge water generated during this sampling event will be removed from the site <br />' during the third quarter by Belshire Environmental Services,Inc and later transported by Nieto&Sons to <br /> DeMenno Kerdoon in Compton,California for treatment and disposal Waste dlsposal documentation will <br />' be forwarded once received <br /> FLUOR DANIEL GTI <br />