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Colowyo PR3 adequacy response memo <br />April 21, 2011 <br />11. Regarding Figure A-1, the following questions/comments should be addressed, and <br />any associated changes in the SEDCAD model should be made: <br />a) It appears that Structure 40 (aka D1) and its drainage area do not extend far <br />enough to the west. On the figure, the channel is truncated at the ridgeline, <br />however, the disturbed area extends beyond the ridgeline, and runoff from <br />part of the disturbed area would not be captured by the drainage system and <br />would not be treated by the sediment pond. <br />b) Why is the ditch in area A26 labeled D15? Is this a mistake? <br />c) It appears that a small area that drains to Structure 19 is missing on the <br />figure. The Subwatershed Hydrology Detail table lists two small tributary <br />areas but only one is shown on the figure. <br />d) For mountain brush areas, the legend in Figure A-1 should indicate a CN of <br />41, not 57. <br />e) For juniper areas, the legend in Figure A-1 should indicate a CN of 73, not <br />63. <br />f) For bare areas, the legend in Figure A-1 should indicate a CN of 91, not 85. <br />g) The area that drains to ditch D7/D8 (Area A-30) needs to extend to north. <br />12. In the design details in Table 7-23C-1, some of the details for the perforated riser for <br />the Little Collom Pond (namely the barrel diameter, barrel length, and barrel slope) do <br />not match these details in the Structure Detail for Structure #1 in the SEDCAD report. <br />13. Within Exhibit 7, Item 26, on the Little Collom Pond Design Drawing, Figure 1, please <br />address the following errors: <br />a) The Area-Capacity table does not match the Elevation-Capacity-Discharge <br />table in Exhibit 7, Item 23. Please confirm which table is correct and that the <br />contours on the figure are correct and match the correct table. <br />b) One of the construction notes has text that has been truncated. <br />c) This figure has references to the floating siphon that must be removed. <br />Rule 4.05.7 Discharge Structures <br />1. Please provide documentation that energy dissipation is not required at the <br />downstream end of the lower clear water diversion or provide the design detail.