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• DDJ*acy OU 1 Pesticide Remi diation Groundwater Extraction Well Installation W rk Plan 1.0 INTRODUCTION AND 1.4 To determine if the operation of PE -1 and BACKGROUND PEW-2 combined with EW040AU and EW041AU can adequately capture the lea Jing 1.1 This work plan describes the proposed edge of the dieldrin plume, aquifer testing will groundwater extraction well installation and be performed on the new wells. During th aquifer testing effort to be conducted at the aquifer testing, water level measurements will be Defense Distribution Depot San Joaquin collected from temporary piezometers installed California Tracy Site(DDJC-Tracy). The around PEW-I and PEW-2. Seven temporary purpose of the proposed extraction wells piezometers will be installed in the Above Upper (PEW-1 and PEW-2), installed as part of Horizon, and three will be installed in the Upper DDJC's ongoing Operable Unit(OU) I ground- Horizon. The temporary piezometers will water remediation efforts, is to provide effective installed using cone penetrometer testing(CPT) capture of the leading edge of the dieldrin plume procedures. CPT dissipation tests will beper- that has migrated beneath agricultural land of the formed to estimate the elevation of the top of the DDJC-Tracy Annex(see Figure 1-1). Above Upper and Upper Horizons. The C dissipation tests and the CPT logs will be valu- 1.2 Extraction wells EW040AU,EW041AU, ated to determine a preferred screen interval for EW042AU, and EW044AU were installed in the piezometers. Drawdown measured in tfie December 1998 to begin remediation of dieldrin piezometers,emplaced at several radial in OU 1 groundwater(Radian International, distances from the wells,will provide an 1999) (Figure 1-1). Specifically,EW040AU and estimate of capture zone width. If drawdown is EW041AU were installed to minimize migration measured in the Upper Horizon piezomete rs,the of dieldrin to the DDJC-Tracy Annex property. potential influence of PEW-1 and PEW-2 n the EW044AU was installed to provide additional Upper Horizon can be characterized. control of dieldrin migration to the Annex, and EW042AU was installed in the Solid Waste 1.5 After well installation and aquifer tes ing Management Unit(SWMU)2/3 area to remove are completed,a report summarizing the r sults dieldrin from groundwater near the former and providing an estimation of the capture zones source area(URS,2002). However,results from of PEW-1 and PEW-2 will be prepared. C nsis- aquifer testing of theses wells in 1999, as tent monitoring of the width of the capture zones presented in the DDJC-Tracy Site OU I when all pesticide extraction wells are in f all Groundwater Treatment for Pesticides, Pre- operation requires water level measurements Design Technical Summary,are insufficient to near the wells in directions that are not do n- assess the wells zones of capture(Radian gradient from the wells. After an evaluation of International, 1999 and URS,2002). Therefore, the lithology from the CPT logs and the ac infer PEW-1 and PEW-2 are proposed for installation test results,some of the temporary piezo ters in the Annex area between EW040AU and will be converted to permanent piezometei s, and EW041AU to provide adequate plume capture. the remaining temporary piezometers will be abandoned. Permanent piezometers are ne ded 1.3 Well vault installation for PEW-1, PEW-2, to provide water level data points cross-gr idient EW040AU,EW041AU,EW042AU, and from the extraction wells. Additional pern anent EW044AU will also be completed under this piezometer locations may be recommende I, if task order(TO). Installation of extraction system the aquifer testing results conclude that the pipeline and electrical conduit to connect the six temporary piezometer locations are inapp - extraction wells to Groundwater Treatment priate for long-term estimation of the capti ire Plants I and 2(TP 1 and TP 2)will be per- zones of PEW-1 and PEW-2. formed under a separate TO.The construction of the extraction system,beginning with the well 1.6 The installation and aquifer testing o headworks,is described in DDJC-Tracy Site PEW-1 and PEW-2 are tentatively schedu ed for OU I Pesticide Remedial Design 100% August 2002. The procedures that will be ised Submittal(URS, 2002). for this work are summarized in the follom ing KA02237\01J 1_Pest-Rem\final\GW-EW-WrkPln.doc I my 2002