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Colowyo PR3 adequacy response memo 4 April 21, 2011 <br />number 3 above, additional information is required regarding the "near source" ponds. <br />3. Regarding the SEDCAD model documentation for the worst-case scenario (Exhibit 7, <br />Item 23), many of the issues previously noted were addressed by Colowyo, however <br />additional deficiencies in the revised model and documentation need to be addressed <br />as noted in the following items. <br />4. The ditch downstream of Area 3 does not extend around the ridgeline on Figures Al <br />and E1 (Exhibit 7, Item 23) as it does on Map 41 B (see Little Bear Draw). Please <br />explain or revise figures. On Figure Al, should area A3 extend to west? Also on <br />Figure E1, the scale bar appears to be wrong. <br />5. Please remove all references to the floating siphon, for example page A-1. <br />6. The Structure Networking table indicates which areas drain to which channels for a <br />few of the channels (for example Structure 6 is fed by Area A-35), but not for most <br />channels. Please provide this information for all channels. <br />7. It is stated in the text of Exhibit 7, Item 23 that Table 1, Part A will be used for CN <br />values used in all current modeling. This table gives a CN value of 91 for bare soil, but <br />the values in the Subwatershed Hydrology Detail table are 85. Please address this <br />discrepancy for bare soil and for any other applicable land use categories. <br />8. On the SEDCAD model overview sketch (figure entitled Network Sketch 7-23A), <br />should the long natural channel drain to structure 5 rather than structure 6? <br />9. Regarding the Subwatershed Hydrology Detail table, the following <br />questions/comments should be addressed: <br />a) It appears that subwatersheds for structures 5 and 6 were interchanged. In <br />particular, it appears that Area A-2c was erroneously included in portion of <br />model for structure 6 and Area A-35 was erroneously included in portion of <br />model for structure 5. <br />b) Was Area A-39a excluded from the model? Perhaps it should be included in <br />portion of model for structure 43. <br />c) Area A-30 should extend to Structure 39 (aka D7/D8). <br />d) The undisturbed portion of Area A-6 appears to have been excluded from <br />the model. Please clarify or add this portion to model. <br />10. Regarding the Subwatershed Time of Concentration Details table, it appears that <br />subwatersheds for structures 5 and 6 were interchanged (related to issue above). <br />This error impacts the times of concentration.