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Work Plan for Groundwater Monitoring Well Installation at the California Army National Guard Stockton Field Maintenance Shop Stockton California —- LJ 1.1 PROJECT OBJECTIVES AND SCOPE The objectives of this project are to: • Delineate the vertical and horizontal extent of impacts to site groundwater from contaminants released from the former USTs at the site; • Determine the direction and gradient of groundwater flow at the site; and • Perform a preliminary evaluation of the potential need for remedial activities to address groundwater contamination at the site. To address the stated project objectives, the following scope of work has been developed: • Install and develop five (5) groundwater wells at the site, including one near the former USTs and in the presumed center of, and four along the approximate margins of, impacted groundwater at the site. • Construct the groundwater wells in a manner that would facilitate use as part of a high vacuum dual phase extraction system or other groundwater remedial system, if necessary. • Have the horizontal location and vertical elevations of each well surveyed by a California -licensed land surveyor. • Implement a monitoring and testing program to determine the direction and magnitude of groundwater flow across the site and to evaluate concentrations of contaminants in groundwater over a period of four quarters. • Implement a quarterly reporting program, documenting the groundwater monitoring • and testing program, for CVRWQCB review. • Develop a preliminary assessment of the need for, and provide recommendations for, future actions and/or site closure, as appropriate to the data, and submit that assessment concurrent with findings from the fourth quarter of groundwater monitoring and testing. All activities associated with the proposed scope of work will be performed to meet the CVRWQCB)'s directives pursuant to the Clean Water Act and California's Porter -Cologne Water Quality Act. 1.2 SITE LOCATION Information provided in this and subsequent sub -sections was derived chiefly from the 2007 URS SI Report. The site is located at 8010 South Airport Way, Stockton, California (Figure 1; Appendix A). The site is one of four divisional areas at the CA ARNG facility, including the Army Aviation Support Facility (AASF), the Armory, and the Combined Support Maintenance Shop (CSMS). The general site layout and related features are show in Figure 2 (Appendix A). 1.3 SITE DESCRIPTION AND HISTORY The Stockton FMS and three other divisional areas are State-owned facilities operated by the CA ARNG. The FMS consists of a one-story maintenance building composed of work bays, supply areas, a latrine, and offices; a vehicle inspection rack; hazardous materials storage sheds; a concrete wash pad with an associated holding tank; and a refueling area consisting of • two dispensers at an island and the location of two former USTs. OTIE