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<br /> .� 4.0 HYDROGEOLOGY
<br /> The site as located within the central
<br /> portion of the physiographic providence known as the Great
<br /> I Valley, The Great Valley is a large elongate northwest-trznding asymmetric structural trough
<br /> that has been filled with a thick sequence of sediments ranging in age from Jurassic to Recent.
<br /> In the study area these sediments consist of a heterogeneous sequence of gravel, sand, silt, and
<br /> clay deposited by the Sacramento River system. The sediments encou»tered during drilling
<br /> consist primarily of an organic soil to approximately.S feet below grade underlain with peat to
<br /> 12 feet. The soil beneath the peat consists of a fat clay to total depth of 15 feet below grade.
<br /> Lithologic logs are presenwl in Appendix I.
<br /> The deposits containing fresh groundwater in the area are principally unconsolidated continental
<br /> deposits of Pliocene to Recent age that extend to depths ranging from lsss than ten to more than
<br /> 3,500 feet. Groundwater was encountered during drilling activities at approx;mately 1.5 feet
<br /> Mow grade.
<br /> S•a FIELD INVESTIGATION
<br /> € To Provide additional informaLon regarding subsurface conditions at the site, RESNA
<br /> ! IndustrieslWaterWork Corp. supervised the drilling of 5 groundwater monitoring wells during
<br /> the months of March and April 1991, The drilling was performed by ExcelTech Drilling of
<br /> Fremont, California, utilizing a hollow-stem auger drill rig. The wells were situated to provide
<br /> information regarding groundwater quality and hydraulic raulic conditions beneath the site(Figure 5),
<br /> 5.1 Sampling Procedures
<br /> All borings were sampled at approximately 1,0 to 2.5 feet below grade using a split-spoon
<br /> sampler with brass Iiners. The brass liners were sealed at each end with aluminum foil and a
<br /> plastic cap. The plastic cap was secured with tape and the sample placed on ice. The soil was
<br /> logged by a qualified geologist using the Unified Soil Classification System. Descriptions of the
<br /> soils encountered and monitoring well details were recorded on the,yell/boring logs(Appendix
<br /> i
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<br /> I j King Island Rmort-347 ..
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<br /> iiiiiii0l OWNS
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