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Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California by shifting the local hydraulic gradient to the east-northeast and improving plume capture by filling a gap in the extraction well network west of the facility, on the leading edge of the plume. • Two monitoring wells (MW549C and MW550C) screened in the C Zone will be installed on the southern edge of the facility to fill data gaps on the south edge of the facility, east of MW440. These wells will aid in defining the southern plume boundary. • One monitoring well (MW551B) screened in the B Zone will be installed offsite west of the Central Area, at Englewood Way and Baywood Way.This well will fill a data gap between MW504B and MW531B, aiding in defining the western plume boundary and monitoring plume migration. • Two monitoring wells (MW551C and MW552C) screened in the C Zone will be installed offsite west of the Central Area. MW551C will be located adjacent to MW551B at the corner of Englewood Way and Baywood Way, and MW552C will be located near the intersection of Christie Falls Way and Waterman Ave.These wells will fill data gaps south and west of the current plume boundary, aiding in defining the western plume boundary and monitoring plume migration. • Previous attempts to establish access agreements with the UPRR have resulted in significant project delays. Installation of EWCB, EWC9, EWCC7, and associated conveyance lines on UPRR property, including final locations and installation schedule, will depend on access agreement negotiations between the Army and UPRR. All wells will be installed according to recommendations presented in the 2021 FFA Annual Report(Ahtna, 2022a). The ten new wells will be added to the existing Groundwater Monitoring Program following installation and development. 1.1 Site Location and Description Sharpe is a distribution depot formerly operated by the Defense Logistics Agency(DLA)to supply military services with the equipment needed to fulfill their missions. Sharpe is located in California's primarily agricultural San Joaquin Valley in San Joaquin County,within the city limits of Lathrop.The unincorporated community of French Camp borders Lathrop to the northwest, and the city of Manteca borders Lathrop to the east. Nearby large urban communities include the city of Stockton, approximately nine miles to the north, and the city of Modesto, about 20 miles south of the depot (Figure 1). Wastes generated at Sharpe were primarily a result of former maintenance operations such as paint stripping, metal finishing, and painting. Other waste-generating activities included engine overhauls, hydraulic and electrical repairs,airframe and bodywork,and component repair and reconditioning.These activities required the use of petroleum hydrocarbon fuels and a variety of other industrial chemicals(e.g., chlorinated solvents). Releases of these chemicals contaminated installation soil and groundwater through various fate and transport processes. Ahtna Environmental,Inc. 2