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Updated Corrective Action Plan—Tosco(76)Service Station No 11192, Stockton, California <br /> June 26 2002 <br /> 41 Pre-Field Activities <br /> GR will update the site-specific safety plan and obtain the necessary well installation permits from the <br /> San Joaquin County PHS-EHD In order to install the off-sate groundwater monitoring wells GR will <br /> obtain encroachment permits from the San Joaquin County Department of Public Works A private <br /> utility locator will be contracted to locate any underground utilities near the proposed well locations and <br /> Underground Service Alert (USA)will be notified 48 hours prior to drilling <br /> 42 Drilling and Sampling <br /> Drilling and well construction activities will be performed by a California licensed driller AGR geologist <br /> will observe the drilling, collect soil samples for chemical analyses, describe the encountered soil, and <br /> prepare a log of the boring The borings will be advanced using 8-inch-diameter hollow-stem augers and a <br /> truck-mounted drill rig Soil samples collected for description and possible chemical analysis will be <br /> obtained from each monitoring well boring at five-foot intervals, at a minimum Soil samples will not <br /> be collected from the sparge point borings Although the actual number of samples submitted for <br /> chemical analysis will depend on site conditions and field screening data,GR anticipates a minimum of <br /> one unsaturated soil sample from each boring will be submitted for chemical analysis <br /> Soil samples from each sampled interval will be screened in the field for the presence of volatile organic <br /> compounds using a photoionization detector (PID) Soil screening data will be collected for <br /> reconnaissance purposes only,and will not be used as verification of the presence or absence of petroleum <br /> hydrocarbons Screening data will be recorded on each boring log <br /> Drill cuttings will be stockpiled at the site pending analysis and disposal Stockpiled cuttings will be <br /> placed on and covered with plastic sheeting Four soil samples from the drill cuttings will be collected for <br /> disposal characterization as described in Appendix A Upon approval from the landfill,the drill cuttings <br /> will be transported by a Tosco-approved soil hauler to Forward Landfill, located in Manteca,California <br /> Water generated during cleaning of the drilling equipment will be stored at the site in properly labeled <br /> drums,pending transportation to the Tosco Refinery in Rodeo, California, for disposal <br /> 43 Monitoring Well and Sparge Point Installation <br /> The groundwater monitoring wells will be constructed of 2-inch-diameter Schedule 40 polyvinyl chloride <br /> (PVC)well casing and 0 02-inch machine slotted PVC well screen The screened interval of the shallow <br /> well will extend from 10 to 30 feet bgs to accommodate known groundwater fluctuations in the area The <br /> screened interval of the deep wells will extend from approximately 70 to 80 feet bgs The four deep <br /> monitoring wells will be constructed inside a 45-foot long 8 625-inch inside diameter permanent steel <br /> conductor casing The conductor casing seals off the shallow aquifer from the deeper aquifer, to prevent <br /> cross-contamination between the two water bearing zones The conductor casing will be installed through <br /> . 15-inch diameter hollow-stem augers The cement seal around the conductor casing will be allowed to set <br /> 140245 08 14 <br />