Laserfiche WebLink
i <br /> SITE CONDITIONS <br /> P <br /> ° HYDROGEOLOGY <br /> € s <br /> The geologic formations in the Stockton area can be <br /> classified into two general groups; semi-consolidated saline <br /> water bearing units and the overlying unconsolidated fresh water <br /> bearing uni_s. The semiconsolidated rock units are <br /> composed of <br /> the Mehrten aid the Valley Spring Formations. These formations <br /> are of volcanic origin and contain andesitic and rhyolitic <br /> breccia, tuff and ash. The groundwater within these two forma- <br /> rj <br /> tions is saline and is separated from the overlying fresh water <br /> r <br /> bearing units by an impermeable bed within the upper Mehrten <br /> Formation. <br /> The unconsolidated units consist of alluvial sediments of <br /> the Victor Formation, Arroyo Seco Gravel and the Laguna <br /> Formation. These formations are compose <br /> d of gravels, sands, <br /> silts and clays which have a total thickness of a <br /> 1000 feet. Good pproximately <br /> xsti quality groundwater is presentin these units <br /> under generally unconfined aquifer conditions, althoughminor <br /> confined aquifers exist. A barrier to saline groundwater ; <br /> intrusion occurs along the west side of Stockton and is formed by <br /> a depositionalcontact between the deltaic deposits to the west,: <br /> and the alluvial deposits to the east. <br /> � f9 <br /> a <br /> The materials immediately underlying the site consist <br /> predominantly of clays and sand with lesser amounts of salt, <br /> _..._ <br /> silty -clay y._, s <br /> y and- silt sand_ The.. first- 12 feet of the boring <br /> encountered fill material from the tank pit excavation Below <br /> the excavation alternating beds of .clayey sand, silty sand, silt ' <br /> i <br /> tj <br /> and clay. were encountered. A 3-5 foot interval <br /> of sand was . <br /> encountered at approximately 26 feet. A thicker interval of fine <br /> sand was encountered at between 45 to 48 feet below the surface <br /> ,,mow <br /> 7 <br /> Y - - - - - ' <br />