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FIIMSTONE Service Center 400 North El Dorado Street, Stockton, California <br /> October 6, 1993 Site Assessment Work Plan-2072 01 Page 3 of 7 <br /> The remaining four borings will be drilled to the east and west of the former tank pit. Each of <br /> these borings will be offset from the excavation boundaries approximately 5-feet. information <br />' obtained from these bonngs will be used to evaluate the degree of horizontal contaminant <br /> migration immediately adjacent to the pit area The horizontal distances and boring locations <br /> were selected based on existing analytical information and physical site constraints. <br /> Ryan-Murphy believes that the preceding array of borings is necessary to characterize subsurface <br /> conditions at this site, and necessary for a reasonable evaluation of potential remediation <br /> strategies. <br /> 4.0 PROCEDURAL OUTLINE <br /> 4.1 Drilling Methods <br /> All boring and sampling activity will be performed as prescribed in the California Code <br /> of Regulations, Title 23, Chapter 16, Section 2644 Initially, all underground utilities and <br /> storm sewers will be marked by the appropriate agencies <br /> Using hollow-stem augers, the bonngs will be drilled to depths sufficient to determine <br /> the vertical extent of contamination Borings will not penetrate any apparent confining <br /> strata such as clay layers or materials impenetrable with augers (boulders, rock) As <br /> stated previously, boring termination depths of less than 30-feet are anticipated <br /> However, borings will be advanced until field observations (photoionization detector <br /> [PID] screening, visuals, etc ) indicate that hydrocarbon impacts are absent <br /> Soil boring depths exceeding 40-feet at this site have not encountered free groundwater <br /> or elevated soil moisture levels Groundwater depth is estimated at approximately 75-feet <br /> at this location Based on this information, the proposed soil borings are not expected to <br /> encounter groundwater, and as such, specific groundwater monitoring well installation <br /> details have not been included in this work plan <br /> If subsurface conditions are such that the planned soil sampling technique does not <br /> produce acceptable results, e g poor sample recovery, another sampling method deemed <br /> more appropriate to the type of soil material present will be used This determination will <br /> be made by the Ryan-Murphy project geologist in conjunction with the drilling contractor <br /> and the Ryan-Murphy environmental division manager <br /> RYAi_MURP W, INCORPORAI M Deaver <br /> F�vironmeatal Constractioo <br /> 4 <br /> 2 Los Angeles <br />