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I I I I I I I I I I I I I I I I I I I In addition to NF1P requirements concerning the regulation of existing hydrologic and hydraulic conditions, the Centre A venue Extension project was also tasked with meeting City of Fort Collins storm drainage criteria which requires that design of the roadway and Spring Creek bridge accommodate estimated discharges based on fully-developed basin conditions, Consequently, the design of facilities identified in this report may be conservative with respect to existing conditions, as all major drainage facilities have also been designed in order to meet the more restrictive City criteria, 1.2 Previous Studies Spring Creek has been the subject of numerous City master planning studies and updates, as well as the implementation of many drainage improvement projects, Of particular note for the current study, Spring Creek was studied as part of the original Flood Insurance Study (PIS) for the City of Fort Collins, and the most recent PIS update [FEMA. 1996], For Spring Creek, the 1996 PIS update was based on revisions completed for the City of Fort Collins in 1993, It is noted that a CLOMR based on design information for the current project (Case No, 99-08-0IOR) was obtained on December 10, 1998, The topographic mapping used for the 1993 Spring Creek revisions represents the best available pre-project mapping for the current study area, This mapping is an orthophoto-based topographic map at a scale of I" = 100' with a contour interval of 2 feet. The two 1993 revisions work maps which provide coverage of the current study area (Sheets 6 and 7) are included with this report. 1.3 Purpose and Scope of Study The primary purpose of the current study is to hydraulically analyze the Centre A venue bridge at Spring Creek for existing runoff conditions as defined by FEMA, along with preparing all requisite information and documentation for submittal to FEMA for a Letter of Map Revision (LOMR) for the Centre Avenue extension and Spring Creek bridge, As mentioned above, due consideration has also been given to the hydraulic analysis of facilities based on fully-developed basin conditions as required by the City of Fort Collins, The fully-developed condition analysis will be documented in a separate report to be completed by Anderson Consulting Engineers, Inc, T:'.oPFN\:ocsrtnl cncsrlDl fema-LOMR final-rpL\\pd 3 ANdERSON CONSulTiNG ENGiNEERS, INC.