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Geosyntec consultants A selection of monitoring wells at Site 3 were historically sampled for groundwater geochemistry parameters. The geochemistry of samples collected from monitoring wells W-002 (screened from 28 to 39 feet bgs), W-025 (screened from 12.5 to 20 feet bgs), and W-052 (screened from 10 to 21.4 feet bgs)were all similar,providing another line of evidence that the monitoring wells at RRI are screened within a single interconnected water-bearing zone (Geosyntec, 2018a). The geochemistry also indicated that groundwater and surface water are connected, as discussed below in Section 2.3.5.2. The geologic logs from borings at RRI were reviewed, and the soil at RRI consists of interbedded peats, clays, silts, and sands with no distinctive or consistent layering in the top 80 feet bgs (Figures 14 to 19; Geosyntec, 2018a). This supports that the wells are screened within a heterogenous zone. Additionally, the logs provide no indication of the presence of laterally continuous clay or sand units separating the top 80 feet bgs into separate aquifers. Consistent with the Navy 2002 hydrogeologic CSM, the soils appear to consist of laterally and vertically discontinuous packages. 2.3.4.1 Properties Soil physical parameter laboratory tests and pumping tests were conducted by the Navy to determine the hydraulic properties of the soils in the water-bearing zone. Of the 277 soil samples collected by the Navy for physical parameter laboratory analysis, 202 soil samples (73%)were classified as predominately clay or silt and 75 soil samples (27%) were classified as sand(Tetra Tech, 2002). The range of vertical (Kv) and horizontal (Kh)hydraulic conductivities estimated by the Navy based on the laboratory analysis and pumping tests are summarized below. Hydraulic Conductivity Ranges at RRI Soil Type Laboratory Kv(cm/sec)' Field Kh(cm/sec)' Sand(silty to well-sorted 2.0 x 10-1 to 5.8 x 10-6 Silt(clayey to sand 2.8 x 10-1 to 5.1 x 10-4 1.3 x 10-1 to 2.8 x 10-' Clay(silty to sand 4.5 x 10-1 to 6.3 x 10-4 Notes: ' Kv is typically at least 10 times less than Kh. ' From slug tests in various wells and pumping tests at Site 3, Site 4,and IAS-11. cm/sec=centimeters per second Groundwater in the water-bearing zone in the top approximately 80 feet bgs at RRI appears to be under unconfined conditions (Geosyntec, 2018a). The drawdown responses observed during the pumping tests conducted by the Navy had estimated storage values and response curves indicative of unconfined conditions (PRC, 1997b; Geosyntec, 2018a). Additionally, a review of the geologic boring logs compared to the first depth to groundwater measurements in the monitoring wells conducted in 2018 indicated that the logged depth of the first wet soil is generally similar to the first depth to groundwater measurement taken in the monitoring wells, which provided another line of evidence that the groundwater at RRI is under unconfined conditions (Geosyntec, 2018a). RRI Groundwater Monitoring Work Plan 12 June 2022