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7 �•;kat - �� _. - .- % - ;$ � ;. - <br /> }Vl <br /> i f•M � <br /> SUMMARY AND CONCLUSIONS <br /> The summary and conclusions presented in this section are based on data <br /> collected for and interpretations developed in this report. The summary and <br /> conclusions are presented in sections :.... 1) field work implementations; 2) <br /> stratigraphy and hydrogeology;3)soil chemistry;and 4)water chemistry. <br /> Field Work Implementations <br /> • Between September 16-23, 1991, ES advanced five soil borings at the GLI <br /> Terminal in Stockton, California. These boreholes were utilized for soil <br /> sampling Iocations. <br /> Soil samples were collected at rive-foot intervals during advancement of the <br /> boreholes with the sample displaying the highest TIV measurement in each <br /> borehole being submitted for chemical analysis. Soil samples were analyzed <br /> for TPHD,TPHG and BTEX. <br /> • Three of the five soil borings were converted to permanent monitoring wells. <br /> The wells were constructed to monitor potential contamination associated <br /> Ath past operations of the UFST system. <br /> • On Sentemher 23, 1991, the wells were monitored for product thickness, <br /> depth to water and water quality. Water quality samples were analyzed for <br /> TPHD,TPHG and BTEX. <br /> Site Stratigraphy and Hydrogeology <br /> • Subsurface materials consist of clayey silts with moderate to well-sorted, fine <br /> sand lenses. <br /> • Shallow groundwater underlying the site occurs under unconfined conditions. <br /> Groundwater was encountered at a depth of 43 feet. <br /> • Groundwater flows to the south,with a hydraulic gradient of 0.002 ft/ft. <br /> • the site is 100 percent paved with asphalt/concrete which should inhibit <br /> vertical and horizontal migration of contamination due to recharge. <br /> Soil Chemistry <br /> TPHG was not detected in any of the samples submitted for analysis. <br /> • TPHD was detected at concentrations ranging from 500 (MW-3) to 6,800 <br /> mg/kg (B-1). 'Be highest detected TPHD concentration was from a sample <br /> collected at a depth of 25.0 to 26.5 feet below ground surface. <br /> Benzene and toluene were not detected in any of the soil samples submitted <br /> r - for analysis. <br /> EShylbenzene was detected at concentrations ranging from 7.2 (MW-2) to <br /> : 600 ug/kg (B-;). Total xylenes were detected only in sample MW-3 at a <br /> concentration of 10 ug/kg. <br /> The RWQCB uses a concentration of 100 mg/kg TPH in soil samples to <br /> initiate groundwater investigations. The JHS uses a concentration of 1,000 <br /> LML/SY132.21/005 REVD <br /> 7 <br /> J <br />