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3.0 CHARACTERIZATION OF SITE GEOLOGY 3.1 Stratigraphy The TVG plant has been built on recent alluvial sediments adjacent to Bear Creek. The subsurface lithologic section was determined by the installation of five soil borings which were extended from the surface to approximately 20 feet below the first encountered water. The boring logs (Appendix I ) were correlated to develop a conceptual model of the subsurface. The lithology of the subsurface shows predominantly clays and silts from the surface to a depth of approximately 40 feet; predominantly sands from approximately 40 feet to 60 feet; and predomi- nantly clays from approximately 60 feet to 80 feet. Field observations indicate that local fracturing exists in the surficial sediments. However there are no indications from the boring logs that any preferential flow patterns or pathways exist in the vadose zone. Site stratigraphy is illustrated on cross sections A-A' and B-B ' , Figures 2 and 3, respectively. 3. 2 Infiltration capacities Three infiltration tests were performed to estimate the percolation rates in the upper three feet of soil . The locations of infiltration tests are shown on Figure 2. Test one resulted in an infiltration rate of 597 minutes/inch. Tests two and three were 0.3 and 14. 5 minutes/inch, respec- tively. Field documentation for the three infiltration tests are contained in Appendix III . The test results indicate infiltration rates can vary significantly in the discharge area. However, the average infiltration rate of 204 minutes per inch reflects a relatively low permeability soil. This is consistent with observations of near-surface soils during drilling throughout the area. Surface soils to a depth of at least two feet are characterized as fat clays in each of the borings. This would suggest that the primary loss of discharged water is to evapotranspiration and that very little water is actually infiltrated. Therefore, rapid infiltration of wastewater which could affect groundwater quality is not likely. Groundwater levels from the site' s monitoring wells should be monitored and evaluated periodically to determine if recharge water is impacting groundwater flow or water quali- ty. 4.0 HYDROLOGIC SETTING The depth to first groundwater below the site varied from 62-67 feet below grade. The groundwater beneath the site flows generally south under a varying gradient. As shown in 4