Laserfiche WebLink
M IN <br /> J, H. KLEIN>=ELDER S,ASSOCIATES <br /> �I <br /> 6 SITE SUBSURFACE MMRAULICS CH"AGTMZdTI(H <br /> r <br /> 1 <br /> 6.1 VADOSE ZONE <br /> The vadose zone ranges from approximately 37.5 feet thick (MW-6) to 44.5 <br /> feet thick (RW-1) as observed during June 1987 (Figures 6 and 7). <br /> Seasonal fluctuations of the vadose zone thickness could occur due to s <br /> variation in the hydrologic cycle and water use patterns. i <br /> The vadose zone is shown on the fence diagram (Figure 7) as including all <br /> t <br /> sediments above elevation (—) 29.0 feet, M.S.L. These sediments encompass <br /> Zones I, II, and III. Zone I has been identified at location MW--6 (Figure <br /> 7) and in soil borings located in the vicinity of fill associated with <br /> closure of the underground gasoline storage tanks (refer to Figures 3, 4, <br /> and 6). Zone I sediments may represent fill material. Zone I consists <br /> of silty sands, thereby providing potential for relatively high vertical <br /> percolation rates. Zone lI consists predominately of silt, thereby <br /> r reducing vertical percolation ' rates for fluids. Zone III consists <br /> predominately of silty sands, thereby providing potential for relatively <br /> high vertical percolation rates. The interrelationships of these three <br /> zones, each located above the uppermost water—bearing unit, are <br /> t f illustrated on geologic cross section A—A' (Figure 6). <br /> c <br /> 6.2 UPPERMOST WATER—BEARING UNIT <br /> 01 i <br /> Six hydrogeological zones were identified from available data and <br /> significant lithological horizons were mapped (Figures 6 and 7). A weakly Yr <br /> confined, uppermost water—bearing unit (Zone IV) and a deeper confined Vicom <br /> aquifer (Zone VI) appear to exist below the site. Hydraulic separation of <br /> unknown magnitude between the two water—bearing zones appears to be <br /> _ provided by an aquitard (Zone V). Well screen positions are shown for all y <br /> t <br /> wells on the geologic fence diagram (Figure 7). <br /> f <br /> 53-87-443 11 <br /> i <br />