2016-09-26_REVISION - M1980244 - Laserfiche WebLink

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• There is a reference to the"Ditch along Road, 6"Deep x 24" Wide". Where is the detail for this ditch? RESPONSE: Detail 5, Section D has been added to Drawing CCVSAII-6, which is provided in Attachment 13. 58. Appendix 10, Drawing CCVSAI I-7 • The first bullet on page 4 of this document indicates runoff was estimated using SCS Curve numbers. The basin parameters listed on Drawing CCVSAI I-7 present"C: 0.50" suggesting the rational method was used. Furthermore, Sedcad output, which does not use the rational method, is provided in Appendix 10. What is the meaning of the"C: 0.50"? If it's not used in the analyses, remove it from the drawing and replace it with appropriate parameters. RESPONSE: Drawing CCVSAII-7 has been revised for clarification. The noted C:50 was a relic and confusing AutoCAD label. The basins have been further detailed using both AutoCAD Civil3D and an updated SEDCAD model. The flow segments are labeled for each basin on Drawing CCVSAI I-7. The segments are duplicated in the SEDCAD model, of which three output files are included as attachments hereto. See Attachment 13. Civil3D labels on the drawing show the up-gradient sheet flow reaches. SEDCAD uses a different"erent method for those areas, of which woodland type terrain was selected. The times of concentration are relatively consistent with both approaches. Photo 3:Stream Channel of Poverty Gulch Adjacent to Basin ChiTunBypass The three SEDCAD files are for 1) 5 yr/24-hr, 2)10 yr/24-hr, and 3)100 yr-24-hr discharges(See Attachment 12). The 5 yr model was used to "calibrate"the SCS Curve Numbers to approximate historical conditions, specifically the flow past the Chicago Tunnel site in the existing stream bed. That stream bed is shown on Photo 3. SAInc staff has been observing storm water management at the site for nearly 20 years and have Page 27 of 30