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Preliminary interpretation by The MARK Group of the data generated by NEESA, Kleinfelder, and ERM-West indicated that existing data do not allow determination of contaminant flow paths or ground-water gradients in the vicinity of the five study areas. The MARK Group identified the following data requirements: • Knowledge of hydraulic continuity between Burns Cutoff and ground water; • Effects of the storm drain system upon ground water; • Seasonal or tidal effects upon ground water and drainage system; • Confirmation of shallow ground-water flow; • Confirmation of regional (intermediate zone) ground-water flow; • Interconnection of shallow and regional zones; • Effect of pumping station and storm drain system upon water quality in Burns Cutoff; • Improved understanding of stratigraphic zones and soil quality; • Improved understanding of ground-water and surface water quality; • Confirmation of vertical migration of volatile organic chemicals from shallow to intermediate zones; • Depth of ground-water below which surface drainage ceases to govern ground-water flow; and • Estimation of hydraulic parameters. Filling these data gaps should provide a framework for design of any subsequent remedial investigation/feasibility study (RI/FS) activities which may be required at NCS Stockton. Subsequently, the Navy determined that an interim site investigation is required to fill these data gaps. In July 1990, The MARK Group prepared an interim investigation work plan for this purpose. Also in 1990, the California Department of Health Services (DHS) and California Regional Water Quality Control Board, Central Valley Region (RWQCB), both provided comments on the Final Draft Interim Investigation Work Plan, Naval Communication Station, Stockton, California. The goals of the interim site investigation are to determine the depth at which surface features (drainage canals, surface water bodies, tides) no longer control ground-water flow and to determine whether or not chemicals previously detected in ground water may be migrating off the island. The interim site investigation is not intended to delineate additional source areas of contamination or provide the data necessary to complete an RI/FS. However, characterization of the geology and groundwater gradients beneath NCS Stockton will provide a framework for planning any subsequent RI/FS efforts, and will facilitate more timely completion of the RI/FS process. PRC intends to adhere to The MARK Group interim investigation work plan as 2