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n <br /> v r <br /> s <br /> Gemin!Petra ra h1c Investi atlons <br /> from the fallowing depths for further laboratory analysis for TPH-G and BTX&E:5.0-5.5',9.5.10.01, 14.5-15.0, <br /> r 19.5-20.0',24.5-25.0',29.5.30.0',34.5-35.0,39.5.40.0',44.5.45,0,and 48,5-50,0', <br /> Predominate lithologies encountered during dr€Iling included low to medium plastic,dense silty clays to 18.0', <br /> with loose, clayey to clean sands from 18.0'to 33,0',and low to medium plastic,dense to very dense clayey <br /> sandy silts, silty sandy clays and silty clays from 33.0 to 50,0'. In the clayey slits and silty clay zones, the <br /> number of blows recorded for the third 6-Inches in all sampling runs were over 40 blow counts and In three <br /> runs, refusal occurred. This woula Indicate very dense material, having very low hydraulic conductivity to <br /> groundwater and/or contaminates. Groundwater was not encountered drilling or present after completion of <br /> the boring. Subsurface iithologies exhiolt coloration Indicative of oxidizing conditions subject to periodic <br /> wetting and drying, in the absence of groundwater. Logs of the boring is located In Appendix A. <br /> Our field observations (lack of petroleum odor) and readings from our HNU Photolonlzatlon Detector(PID) <br /> did not €ndicate any contamination at the time of sampling. The soil boring was backfilled with a <br /> bentonite/cement slurry,with Ms.Darlene Reuss,San Joaquin County Public Health Department on site during <br /> backfllling, <br /> D. ANALYTICAL TESTING <br /> Sample collected durlog this invF a€gation were submitted under chain-of-custody protocol to Superior <br /> Analytical Laboratories,Inc.of Mar,,-az,a DOHS Accredited laboratory.Parameters analyzed Include TPH-G <br /> and BTX&E, while organic lead analysis not performed as initial soil sampling indicated below natural <br /> abundance concentrations for lead, <br /> SITE DESCRIPTION <br /> A. SITE GEOLOGY <br /> Based on this investigation and a review of geological data obtained from California Division of Mines and <br /> Geology publications and other investigations in the vicinity, the site is underlain by very gently dipping <br /> Quaternary fluvial sediments predominately of interlayered dense, low to medium plastic silty clays, clayey <br /> silts,and fine to medium grained clayey to clean sands.Gravel lens or layers were not encountered In the soil <br /> boring. The topographic is slightly Irregular with generally a southwest slope. Underlying the Quaternary <br /> sediments are Mid-Tertlary to recent sediments of continental origin, with Pre-Cretaceous to Mid-tertiary <br /> sediments of marine origin stratigraphically below the continental deposits <br /> S. SITE HYDROLOGIC CONDITIONS <br /> This Investigation confirmed that the groundwater level has drastically been lowered due to draught conditions <br /> and excessive groundwater pumping In the Central Valley at this and adjacent sites. Groundwater was not <br /> encountered or present in the boring upon completion at 50 feet.This Is in agreement with a initial investigation <br /> performed at 4648 East Waterloo Road in 1988. The nearest surface water is the Stockton Diversion Canal <br /> approximately 1 mile southwest of the site. The Cana;is unlined and flows to the northeast.Since groundwater <br /> data is lacking for this and adjacent sites,the assumed groundwater flow direction for this site Is based on <br /> 4 <br />