Permits & Development - Encroachment(EP)/Driveway(DW) Permits - 2007_EP-07-301 thru EP-07-400_ - EP-07-329

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SUMMARY OF CPT WORK TO BE PERFORMED BY URS CORPORATION NORTH OF THE SHARPE ARMY DEPOT IN NOVEMBER 2007 The purpose of this work plan is to describe cone penetrometer testing(CPT)field activities to be performed as part of the Defense Distribution Depot San Joaquin California, Sharpe Site's (DDJC-Sharpe)ongoing groundwater remediation efforts. The objective of this proposed groundwater investigation at DDJC-Sharpe is to determine the extents of trichloroethene(TCE) and tetrachloroethene(PCE)exceeding detection limits in the B and C aquifer zones, beneath the off-depot area north of the Depot. The data will be used to determine whether VOC concentrations may affect potable water wells in the future, in conjunction with the groundwater model. At all locations, samples of groundwater will be collected in sandy intervals at two or three depths greater than 80 feet below ground surface. Sampling depths will be selected using lithologic data and previous sample results from nearby groundwater monitoring wells. Prior to sampling, lithology of potential target intervals for screening will be determined from geophysical data collected by the CPT probe. Groundwater sampling will be conducted using a CPT rig,which consists of a hydraulically powered probe driven into the ground. Sampling tools and rods with approximately 2-inch diameters are advanced into the ground by applying weight, with no soil cuttings generated.No soil sampling or coring will be performed. CPT-interpreted lithology readings are obtained from the initial push at each location;then,a second push will be completed adjacent to the initial push to obtain groundwater samples based on interpreted lithologic and pore-pressure data obtained from the CPT boring. A stainless steel HydroPunch® sampler will be attached to the CPT rod and driven to the desired depth to be sampled. Once at the desired depth,the sampler will be retracted approximately 1 foot to allow formation water to enter the sample chamber through the screen. Groundwater samples will be collected using a stainless steel bailer. Groundwater samples will be transferred to laboratory-prepared sample bottles, labeled, and placed immediately into a chilled cooler for storage and transport to an off-site laboratory. Following completion of sampling activities, each boring will be filled with a neat, non-shrinking cement grout. The cement grout will consist of a mixture of Type II Portland cement or equivalent with 3 pounds of powdered nonbeneficiated bentonite and 7 gallons of water per 94- pound sack of cement. Grout materials will be weighed and metered by the amount of water used. The cement grout will be mechanically mixed with a paddle-type mixer and tremied in place. No accelerator will be added to the grout. The grout will be placed from the total depth of each borehole to approximately 4 feet bgs, with native fill material filling the top few feet of the boreholes; the purpose of this procedure is to restore the borehole locations to their pre-drilling condition.