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1• H. KLEINFEEDER &ASSOCIATES • Lithologic unit tzansitions which represent changes in , depositional energy, are prominent throughout the site. 0 Elevations of hydrogeologic zone interfaces are variable throughout the site. i u Site topography is flat, no relief. E Assessment of the depositional environment of near--surface sediments provides guidance when correlating lithology and stratigraphy between soil boring and monitoring well locations. Based on the artificial penetration lithology logs (refer to Appendix D) and using the location of present-day rivers and deltas, the former depositional environment can be deduced. It is likely that the near-surface sediments observers below the project property result from either a flood plain depositional environment (fluvial) or interd=stributary bay. A description summarizing characteristics of each depositional environment follows: ` • Interdistributary bay deposits are closely associated with delta . topset deposits. Such areas are open water bod•�es surrounded by levees or marshes but are open or connected to the open sea by tidal channels. Deposition in such bays occurs mainly by two Processes: The fine-grained sediment deposited from suspension due to absence of wave activity, and the coarse sediment brought in by crevasse channels. Locally, as a result of the presence of wave activity, lenticular bedding is generally the most abundant type of bedding. a Flood basins are thelowest-lying part of a river flood plain. They are poorly drained, flat, featureless areas of little or no relief located adjacent to active or abandoned stream channels. ` Flood basins act as settling basins in which suspended fine-grained sediment settles down from over bank flows after the coarser sedimenta have been deposited on levees and crevasse splays. Flood basin deposits s re resent the long-continued F p 53-87.443 9