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• DDJC-Tracy GMS Boundar0kndition Verification Work Plan l ES.0 EXECUTIVE SUMMARY of this field activity will support this modeling effort. ES1.1 The Defense Depot San Joaquin (DDJC)-Tracy installation is currently 1.3 The specific field activities to be performed implementing various investigation, design, and to verify the boundary conditions at DDJC- remediation activities for contaminated soils Tracy include the following: and groundwater. These efforts are in support of the Installation Restoration Program(IRP), • Collecting groundwater elevation data Resource Conservation and Recovery Act from 23 off-site cone penetrometer (RCRA),Comprehensive Environmental (CPT)locations within a 1/2 to 1-mile Response, Compensation,and Liability Act radius of the DDJC-Tracy facility; and (CERCLA), Superfund Amendments and Reauthorization Act(SARA), and other • Determine the surface elevation at each regulatory driven environmental programs and CPT location. activities. 1.4 The upper 200 feet of the subsurface ES1.2 The work to be performed within this beneath DDJC-Tracy consists of sand, silty work plan will include collecting information to sand,clayey sand, and gravel layers separated verify the groundwater boundary conditions at by silt and clay layers; groundwater is DDJC-Tracy. The objective of these field encountered at approximately 20 feet below activities is to provide this boundary condition ground surface (bgs). Groundwater flow beneath information to support modeling of the the installation is generally to the northeast, but groundwater at DDJC-Tracy.The groundwater pumping from extraction wells has altered the modeling is being performed by U.S. Army hydraulic gradient in some areas. Groundwater Corps of Engineers(USACE)Waterways occurs in a series of distinct aquifer zones that Experiment Station(WES)to model the flow are interconnected to varying degrees. These and transport of contaminants present in the aquifer zones have been defined as the Above groundwater at DDJC-Tracy. Upper,Middle, Lower,and Below Lower. Where they are present, confining layers of ES1.3 Results from this field effort will be these zones consist of laterally discontinuous documented in an engineering technical clay, silty clay, and sandy clay layers. memorandum(ETM). 2.0 PLANNED ACTIVITIES 1.0 INTRODUCTION 2.1 To support groundwater modeling at 1.1 The purpose of this document is to describe DDJC-Tracy,23 off-site CPT locations will be the specific field activities under delivery order pushed within a 1/2-to 1-mile radius around the (DO)27 (U. S. Army Corps of Engineers, facility. The locations of the CPT borings will Huntsville [CEHNC], Contract Number be placed within the right-of-way of existing DACA87-95-D-0001)to be performed in roads around the DDJC-Tracy facility. These support of the Groundwater Monitoring System locations are shown on Figure 2-1. CPT (GMS)project under TO 24 at DDJC-Tracy in dissipation tests will be performed to estimate Tracy, California. the elevation of the top of the A Zone. Temporary 3/4-inch piezometers will be 1.2 Ongoing modeling efforts at DDJC-Tracy installed next to the CPT locations to provide a by WES include flow and transport modeling of more accurate groundwater elevation reading. the contaminants present in the groundwater at The results of the CPT dissipation test will be DDJC-Tracy. Field work to be conducted as part used to determine piezometer screen location. RPoundwater elevation and surface elevation t-gms-wp MAY10 !999 1 30 April 1999 ENVIRONMENTAL HEALTH PERMIT/SERVICES