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Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California Ahtna Environmental, Inc. 1 1.0 Introduction On behalf of the U.S. Army Environmental Command and the U.S. Army Corps of Engineers (USACE) Sacramento District, per Contract W91238-19-C-0018, Ahtna Environmental, Inc. (Ahtna) has prepared this Groundwater Well Installation Work Plan (Work Plan) for Sharpe Army Depot (Sharpe). The Work Plan describes the installation of two extraction wells (one new and one replacement) and five new monitoring wells. These wells will expand the existing Operable Unit (OU) 1 remedy to remediate volatile organic compounds (VOCs) contamination in groundwater through extraction and treatment. Proposed Well Installations Proposal Well Type Zone Name Figure New Extraction C Zone EWNC7 10 New Monitoring B Zone MW543B 9 New Monitoring B Zone MW544B 9 New Monitoring B Zone MW545B 9 New Monitoring C Zone MW546C 10 New Monitoring C Zone MW547C 10 Replacement Extraction A Zone EWA1R 12 A new extraction well (EWNC7) will be located west of the North Balloon (SHAD-007 & -008), near the MW527R well cluster and will be screened in the C Zone. Five new monitoring wells will be installed in the South Balloon-Central Area, with three in the B Zone and two in the C Zone. The replacement extraction well (EWA1R) will also located in the South Balloon area and will be screened in the A Zone. All wells will be installed according to recommendations presented in the Federal Facilities Agreement (FFA) Annual Progress Report: October 2017 – September 2018 (Ahtna, 2019b). Following installation and development, the seven new wells will be added to the existing Groundwater Monitoring Program. 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, approximately 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.,