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I I I I I I I I I I I I I I I I I I I . Water surface contours plotted at irregular intervals . Preliminary or surveyed HEC-2 cross sections plotted Flood Insurance Rate Map (fIRM) . Published by FEMA . Effective date: February 15, 1991 . Contour interval: No contours . Scale: I inch = 1,000 feet . Datum: National Geodetic Vertical Datum of 1929 . Regulated lOO-year and 500-year flood boundaries and floodway plotted on map . Water surface elevations plotted at 1 foot intervals . Cross sections plotted (extended sections) . Roadways and street names are shown along with flood insurance zones USGS 7.5 Minute Quad Ml\Ps (Pipestone North and Pipestone South. Minn ) . Map dates: 1967 . Contour interval: 10 feet . Scale: 1 inch = 2000 feet . Datum: 1927 North American Datum Aerial PhotoW<lph of Pipestone. Minnesota . Map Date: May 13,1991 . Scale: 1 = 800 feet According to the FIS, cross-sections for use in the hydraulic model were field surveyed, According to the FIRM, the published water surface elevations are tied to National Geodetic Vertical Datum of 1929 (NGVD 1929), Therefore, the surveyed cross-sections used in the FIS HEC-2 model were assumed to be tied to the same datum. All of the conceptual designs for the proposed improvements for this study were based on the results of a proposed conditions HEC-2 model, which is also based on NGVD 1929, Proposed Improvements Analyses for the improvements included evaluation and conceptual designs of proposed levees, channels, and interior drainage facilities along the Main Ditch. In addition, anticipated levee effects on existing flood boundaries were evaluated and preliminary cost estimates for 100-year and 500-year levels of protection were developed, 9th Street NE to IJ.pstream Study Limit The proposed improvements along this reach consist of removing excess vegetation and debris from the existing channel and constructing new levees. Water surface elevations from the 6