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. MASTER DRAINAGEW A Y PLAN PIONEER DITCH AT STERLING,COLORADO . APPENDIX A 1. INTRODUCTION At a meeting held during August 1994, the City of Sterling, Colorado, requested that the following information be provided to them as part of the Section 22 study; (1) plots of existing and design cross sections along Pioneer Ditch, (2) design velocities and cross-sectional areas at bridge locations along Pioneer Ditch, (3) Pioneer Ditch HEC-2 files for existing and design conditions, and (4) a sketch of the Sand and Pawnee Creek 100-year flood boundary at the downstream end of Pioneer Ditch showing the flood plain area reduced by the detention pond and channel improvements along the ditch. This appendix addresses each of the items listed above. 2. CROSS SECTION PLOTS There are two sets of cross sections enclosed in this appendix--those representing existing conditions along Pioneer Ditch and those representing design conditions. The existing conditions cross sections were taken from HEC-2 files compiled by Resource Consultants, listed in reference 2.1 of the main report. When the information was available, overbank sections were combined with channel sections to provide the City with one working model. There are some sections where overbank information was not available; therefore, only the channel is shown on the plots and in the HEC-2 file. Each cross section has two plots included in the packet. The first is an overall plot showing the overbanks and channel configuration. The scale on the overall plots varies drastically due to the variation in the depth of the channel and the width of the overbank sections. The second plot is an enlargement of the channel area plotted at the same scale as the other channel sections. For design conditions, existing sections were modified to include bridge and channel improvements described in Tables A1-A3. 3. CHANNEL AND BRIDGE IMPROVEMENTS Table Al summarizes the five reaches that require benns and/or channel improvements to contain the lO-year future local drainage flood. Table A2 shows existing and design bridge data, including cross-sectional areas and velocities, for bridges recommended for primary improvement. Those bridges recommended for secondary improvements are described in Table A3. Primary bridges are those that need to be modified, with the detention pond and channel improvements described in Table AI, in order to contain the design flood. Secondary bridges are those that do not cause the design .