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I <br /> December 16, 1992 WAANAM <br /> Unocal Service Station No 6981, Stockton, California Working To Restore Nature <br /> 1 <br /> Evaluation of Ground-Water Gradient and Flow Direction <br /> RESNA and GeoStrategies Inc evaluated the elevation of the ground-water surface in each <br /> 1 well to provide an indication of the direction of ground-water flow beneath the site The <br /> monitoring wells were surveyed by a licensed land surveyor to provide the elevation of each <br /> wellhead relative to mean sea level A copy of the surveyor's map is included in Appendix <br /> C The depths to ground water in the monitoring wells were measured during each <br /> sampling event These depths to ground water were combined with the top of the well <br /> casing elevations to evaluate the groundwater gradient and direction of groundwater flow <br /> Data collected during sampling events were used to prepare Potentiometric Maps <br /> Potentiometr►c information is presented in the Site Hydrogeology section of this report <br /> LaboratoDLADalyses <br />► i <br /> Soil and water samples were submitted to various State-certified laboratories for the <br /> requested analyses Table 3 summarizes the laboratories used, analyses requested, and <br /> methods of testing employed Copies of the Chain of Custody Records and laboratory <br /> reports for soil and groundwater samples are included in Appendix D <br /> Vapor-Extraction_Test <br /> _ a t,xtracfion fest onsite fln_ ach 24,4492.-t)-eualuate-the us�Qf j <br /> vapor extraction as a method for remediating vadose soil, the capillary fringe and ground <br /> water (RESNA, June 29, 1992) Vapor-extraction wells VW-1 through VW-4 were used <br /> during the test Results of the test were used to evaluate the effective radius of influence <br /> for the site ")fie efectnv_Q_jadttts ofinfltrenreq-'defined as4thq radial Xistknce from a vapor <br /> extr cttbri <br /> We_ within-which recorded varum icvgl-s indi .at c4—i-t substifface- fiowrate� <br /> 1 <br /> art sufficient for remediation <br /> 38032-L0 8 <br />