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GENESIS ENGINEERING 8 REDEVELOPMENT The Site is located near the center of the Central Valley Geomorphic Province, an asymmetric synclinal trough characterized by extremely thick alluvial deposits on the western side of the axis. Surficial soils are the result of continental alluvial deposition in the flood plains of the San Joaquin and Stanislaus Rivers, and because of the structural down- warping, the overall alluvial section is up to 25,000 feet in the vicinity. The valley extends for 400 miles with a northwesterly trend and is about 50 miles wide at the latitude of Ripon. The near-surface soil profile is characterized by unconsolidated silty and clayey soils with irregular lenses of sand and gravel, typical of overbank fluvial deposition occurring during the Holocene Epoch (Norris and Webb, 1990). To date,the Site has been characterized by the collection of reconnaissance soil and groundwater sampling, gridded soil sampling, and quarterly sampling of the groundwater monitoring well network associated with the Site. The current monitoring well network and lines of the geologic cross sections are shown on Figure 3, and the boring logs and well construction details are included in Appendix A. The Site is underlain by interbedded layers of sand, silty sand, clayey sand, sandy silt, and silty clay(Figures 4 and 5). Individual layers varying in thickness from 1 foot to 25 feet, and layers greater than 2 feet thick can be correlated between borings that are 100s of feet apart. Groundwater is first encountered at approximately 25 feet below ground surface ("bgs"). The shallow water bearing unit is approximately 35 feet thick, with the upper boundary the water table and the lower boundary consisting of a continuous layer of silt and clay at a depth of approximately 60 feet bgs. The groundwater gradient across the Site is low(i.e. —0.0005). The groundwater flow direction is highly variable, however, flow directions are primarily bimodal to the southeast and to the northwest. 1.3 Constituent of Potential Concern Investigation and quarterly monitoring activities associated with the Site have identified nitrate as the Constituent of Potential Concern("COPC")in shallow groundwater. The distribution of nitrate in shallow groundwater during the Second Quarter 2013 is shown on Figure 3, and quarterly groundwater monitoring data since 2005 are shown on Table 1. 1.4 Nitrate Mass and Groundwater Volume Calculations In order to quantitatively evaluate the effectiveness of the groundwater extraction system, initial estimates were made of the mass of nitrate and the volume of water that has been impacted in the shallow groundwater zone(i.e. between 25 feet and 60 feet bgs). Nitrate mass in shallow groundwater was estimated using the nitrate concentration contour map (Figure 6), a porosity estimate, and the thickness of the shallow groundwater zone. RF.Land Inc. 2 of I I Groundwater Extraction Work Plan October 2014