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Engineers (USAGE) in October 1963. The report, "Flood Plain Information, •tropolitan Region, Denver, Colorado, South Platte River, Waterton to ..rig}ton, Colorado", is based on hydrology which is considered outdated and does not consider development changes orhicli have taken dace within the study reach since its publication. Theses changes include new channel allignment, reconstruction of Henderson Road and bridge, construction of several levees and ur- banization upstream. Base hydiulugic data for this study included widely sl.aced field surveyed cross sections, and base mapping enlarged from USGS 7s; gradrangle maps. Even through the study remains the official flood plain designated by the Colorado Wa;er Conservation Board, the data were not used to identify the 100-year flood plain on the mining site. A more recent study has been undertaken by the Federal Insurance Administration (FIA). This study was based on more up-to-date hydrology and included some important changes like the reconstruction of Henderson Road and bridge. The level of detail for this study is consistent only with its purpose,~which is the establishment of flood-insurance rate maps. Base hydrologic data inclurl~ the 1963 Corps of En- gineers surveyed cross-sections, :,~L_plementcd by a few additional cross-sections at key locations, a~td base mapping enlarged from USGS 7'--; minutc• yuadrangle maps. Although the study has not been officially released, it contains the most recent hydrologic information. Prelim- inary hydraulic information incl 'inq flood plain elevations, depths and velocities, and floodwey data was obtained to help with this analysis. .The Urban Drainage and Flood Control District (UDFCD) is in the process of preparing a flood hazard area delinea- tion study for the ... ea. It will include further refinement of the flood hydrology and detailed topographic mapping. Mapping having a scale of 1 inch to 200 feet and a contor interval of 2 feet was obtained from the UDFCD. No hydraulic calculations are presently available frr this study. flood profile from the FIA study was pl~~ted on the de, led 1 inch to 200 `'et topoyral.:aic mapping of the UDI'CD study (Plates I,II, and II1). Analysis of the flooded limits reveals one major inconsistaticy: a levee un the west bank of the South Platte River separates flow on the left overbank from flow in the channel for ~ considerable reach in the mining site. The separation of flows would indicate th flooding on the overbank may act independently of the flow in the channel. A more detailed analysis would be required to establish precisely the flood characteristics on the left overbank, which affects the site most directly. On May 5, 1973, a significant flood was ex~ -fenced on the South Platte River. The flood event approximated the '00-year peak discharge. The peak di •harge was estimated -25-