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L <br /> I <br /> CHAPTER 6 7 <br /> RECOMMENDATIONS FOR <br /> . POST CLOSURE MONITORING <br /> i <br /> ?I <br /> Based bn the results of the work performed to date, and discussions with the San Joaquin <br /> County Public Health Services Department(County)and Sheldon Oil Company(Sheldon),Brown <br /> and Caldwell (BC) recommends thLe installation of three groundwater monitoring wells an <br /> b d the <br /> implementation of a post-closure groundwater monitoring program at the closed underground <br /> storage tank (UST) area of Kent's Oil facility in Stockton, California. A work plan for the <br /> installation and sampling of the groundwater monitoring wells will be prepared and submitted <br />{ to the County for approval. <br /> s Following approval of the work plan, three wells will be installed to a total depth of 100 ' <br /> rfeet below ground surface in the immediate vicinity of the backfilled excavation (Figure 6-1). <br /> Groundwater samples will be collected from the wells and analyzed for the presence of benzene, r <br /> toluene, ethylbenzene, and xylenes (BTEX) by Environmental Protection Agency (EPA) Method <br /> 8020 and for total petroleum hydrocarbons as gasoline (TPHg), diesel (TPHd) and motor oil <br /> (TPHmo) following EPA Method 8015, modified. Sampling will be conducted on a quarterly <br /> basis for two years, or,-until total petroleum hydrocarbons (TPH) are not identified -in all <br /> groundwater,samples for a period of four consecutive quarters -of sampling: <br /> Post-Remediation Groundwater Monitoring Reports will bere ared and submitted to <br /> P P <br /> the County and the Central Valley Regional Water Quality Control Board on a quarterly basis, <br /> following Sheldon's approval. These reports will document the concentrations of constituents t <br /> identified in the groundwater samples collected from the wells as well as the hydrogeologic <br /> conditions encountered at the facility on the date of sampling. At a minimum, the reports will <br /> contain the following information: <br /> • a summary of the activities conducted on-site during the <br /> proceeding three month period, <br /> • a site plan depicting the locations of on-site monitoring wells, <br /> i <br /> • static water level measurement and average groundwater flow <br /> direction as well as pertinent geologic and hydrogeologic <br /> illustrations, <br /> a summary of the analytical results of the groundwater samples, } <br /> and associated figures illustrating the same information, <br /> i <br /> r <br /> Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document. <br /> 17P-ZM9 E-V603\R FP0RTW1)MN ,01L.CLO <br /> OMS-PS22CO <br /> 1 <br /> R <br /> f <br />