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• DDJOracy OU 1 Pesticide Remediation Groundwater Piezometer Abandonment and Installation Work Plan 1.0 INTRODUCTION AND abandoned.Permanent piezometers are needed BACKGROUND to provide water level data points crossgradient from the extraction wells.When installed,the 1.1 This work plan describes the proposed temporary piezometers were not completed as groundwater piezometer abandonment and permanent monitoring points;i.e.,the well installation effort to be conducted at the Defense construction included only filter pack and a Distribution Depot San Joaquin California Tracy bentonite seal placement;no grout was installed. Site(DDJC-Tracy).Extraction wells(EWs) Therefore,all 10 of the piezometers will be EW047AU and EW048AU and 10 temporary abandoned,and the piezometers determined to piezometers(TPZs),TPZI through TPZ10,were become permanent are planned to be reinstalled installed in 2002,and aquifer testing was near their original temporary locations. performed to provide more effective capture of the leading edge of the pesticide(dieldrin) 2.0 TEMPORARY PIEZOMETER plume that has migrated beneath agricultural ABANDONMENT land of the DDJC-Tracy Annex(see Figure 1-1). This effort was completed as part of DDJC's 2.1 Based on the aquifer test results,the ongoing Operable Unit(OU) I groundwater temporary observation piezometers were remediation efforts. recommended to be either abandoned or converted to permanent piezometers.Four of the 1.2 To determine if the operation of EW047AU 10 piezometers were recommended to be and EW048AU combined with EW040AU and abandoned:TPZ3,TPZ5,TPZ6, and TPZ8 EW041AU could adequately capture the leading (URS,2004b).Abandonment will be performed edge of the dieldrin plume,aquifer testing was according to the general procedures described in performed on the new wells. During the aquifer the DDJC-Sharpe/Tracy Comprehensive Field testing,water level measurements were collected Work Plan Field Procedures(URS,2004c).All from the 10 temporary piezometers. Seven abandonment procedures will be performed in temporary piezometers were installed in the accordance with federal, state, and county Above Upper Horizon,and 3 were installed in regulations to assure that the quality of the the Upper Horizon.Drawdown measured in the groundwater is protected and possible physical piezometers provided an estimate of capture hazards to humans is eliminated. zone width. The results from the aquifer testing were documented in the DDJC-Tracy Operable 2.2 As the casing is pulled out of the ground, Unit I Pesticide Remediation Aquifer Test grout will be injected to fill the boring. In the Results for EW047AU and EW048AU(URS, event that the casing breaks or the soil collapses 2003), around the casing,preventing it from being pulled out,the boring will be drilled out using 1.3 After an evaluation of the lithology from hollow-stem auger techniques and backfilled the extraction well borings and the aquifer test with grout. results,a memorandum was prepared(and later revised to address CESPK review comments on 2.3 Cement grout will consist of Type II the original memorandum) to make recom- Portland cement with 3 pounds of powdered mendations for those piezometers that were to non-beneficiated bentonite and 7 gallons of become permanent and those that should be water per 94-pound sack of cement.The cement abandoned(URS,2004a; URS,2004b). As grout will be mechanically mixed with a paddle- described in the DDJC-Tracy Operable Unit I type mixer and then tremied in place.No Pesticide Remediation Groundwater Extraction accelerator will be added to the grout. Well Installation Work Plan(URS,2002), some of the temporary piezometers were to be 2.4 For the piezometers recommended to be converted to permanent piezometers,and the made permanent,a new boring will be drilled remaining temporary piezometers were to be K:\Wpr Ms\00701\Tracy\0UI Pst PZ Abnd\DRAFNext.dM I Jme 2004