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r <br /> %MMA <br /> Mr. Harlin Knoll, SJCEHD September 29,2005 <br /> Site Investigation Work Plan <br /> 103 North E Street, Stockton,CA <br /> Page 2 <br /> To meet these objectives, Stratus proposes a two-phase assessment of site conditions. <br /> The first phase will consist of twelve cone penetration test (CPT) borings advanced to <br /> depths of up to 150 feet below ground surface (bgs). The CPT equipment generates a <br /> continuous log of the subsurface materials encountered, allowing a detailed <br /> understanding of stratigraphic conditions and identification of potential migration <br /> pathways (sandy, transmissive strata). Depth-discrete groundwater samples will be <br /> collected from within these potential migration pathways to further constrain the extent of <br /> 1,2-DCA impact. <br /> Based on the hydrogeologic framework developed from the CPT data, and the extent of <br /> 1,2-DCA impact indicated by the depth-discrete samples, Stratus will then propose <br /> installation of a monitoring well network. This monitoring well network will provide <br /> repeatable sampling points to verify 1,2-DCA concentrations and extent, and evaluation <br /> of groundwater flow beneath the site. <br /> It is Teichert's intention to move this project toward NFA status with all possible haste. <br /> To this end, monitoring well installation activities may also include installation of other <br /> wells necessary to perform remediation feasibility testing, if warranted. These may <br /> include (but not necessarily limited to) ozone sparging wells, oxidant injection wells, and <br /> groundwater extraction wells. Stratus will present the results of the depth-discrete <br /> sampling to SJCEHD, and will discuss installation of feasibility testing wells with <br /> SJCEHD prior to submittal of a well installation work plan. <br /> BACKGROUND <br /> Disposition of Underground Storage Tanks <br /> Two gasoline and one waste oil underground storage tanks (USTs) were removed in <br /> 1986. One additional gasoline UST was removed, and one new gasoline and one waste <br /> oil UST were installed, in 1988. Three diesel USTs. were removed in 1999. One waste <br /> oil UST was removed in 2000. <br /> Subsurface Investigations <br /> Investigation of impact to soil and groundwater beneath the site was initiated in 1986. <br /> Between 1986 and 1999, twelve groundwater monitoring wells (MW-1 through MW-5, <br /> MW-9 through MW-14, and AS-1) were installed and fifteen exploratory soil borings <br /> (B-1 through B-9, B-11, B-14 through B-17, and B92-1) were advanced to evaluate fuel <br /> hydrocarbon impact to soil and groundwater. Groundwater monitoring well and soil <br /> boring locations are shown on Figure 2, and soil analytical data is included in <br /> Appendix A. <br /> K:Micher1lStockton-1031Work PlansVeichen workplan 09-2005.doc 5TKATU5 <br />