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7 <br /> SUMMARY OF OF <br /> WORK TO <br /> BE <br /> DEPOT SIN NO PERFOD BY STION NORTH <br /> M 3ER 007 <br /> s to describe cone penetrometer testing(CPT)field activities to be <br /> i <br /> The purpose of this*p � p <br /> performed as part of the Defense Distribution Depot San Joaquin California, Sharpe Site's <br /> (DDJC-Sharpe)ongoing groundwater remediation efforts.The objective of this proposed <br /> groundwater investigation at DDJC-Sharpe is to determine the extents of trichloroethene(TCE) <br /> and tetrachloroethene(PCE)exceeding detection limits in the B and C aquifer zones,beneath the <br /> off-depot area north of the Depot.The data will be used to determine whether VOC <br /> concentrations may affect potable water wells in the future, in conjunction with the groundwater <br /> model. <br /> At all locations, samples of groundwater will be collected in sandy intervals at two or three <br /> depths greater than 80 feet below ground surface. Sampling depths will be selected using <br /> lithologic data and previous sample results from nearby groundwater monitoring wells. Prior to <br /> sampling, lithology of potential target intervals for screening will be determined from <br /> geophysical data collected by the CPT probe. <br /> Groundwater sampling will be conducted using a CPT rig,which consists of a hydraulically <br /> powered probe driven into the ground. Sampling tools and rods with approximately 2-inch <br /> diameters are advanced into the ground by applying weight,with no soil cuttings generated.No <br /> soil sampling or coring will be performed. CPT-interpreted lithology readings are obtained from <br /> the initial push at each location;then,a second push will be completed adjacent to the initial push <br /> to obtain groundwater samples based on interpreted lithologic and pore-pressure data obtained <br /> from the CPT boring. A stainless steel HydroPunch®sampler will be attached to the CPT rod and <br /> driven to the desired depth to be sampled.Once at the desired depth,the sampler will be retracted <br /> approximately 1 foot to allow formation water to enter the sample chamber through the screen. <br /> Groundwater samples will be collected using a stainless steel bailer.Groundwater samples will be <br /> transferred to laboratory-prepared sample bottles, labeled,and placed immediately into a chilled <br /> cooler for storage and transport to an off-site laboratory. <br /> Following completion of sampling activities,each boring will be filled with a neat,non-shrinking <br /> cement grout.The cement grout will consist of a mixture of Type II Portland cement or <br /> equivalent with 3 pounds of powdered nonbeneficiated bentonite and 7 gallons of water per 94- <br /> pound sack of cement. Grout materials will be weighed and metered by the amount of water used. <br /> The cement grout will be mechanically mixed with a paddle-type mixer and tremied in place.No <br /> accelerator will be added to the grout.The grout will be placed from the total depth of each <br /> borehole to approximately 4 feet bgs,with native fill material filling the top few feet of the <br /> boreholes;the purpose of this procedure is to restore the borehole locations to their pre-drilling <br /> condition. <br />