2023-10-31_REVISION - M1973021 ‎(2)‎

• Permit No: M1973021
• IBM Index Class Name: Revision
• Doc Date: 10/31/2023
• Doc Name Note: Attachment B - Final Phase III Drainage Report
• Doc Name: Request for Technical Revision
• From: Holcim - WCR, Inc.
• To: DRMS
• Type & Sequence: TR9
• Media Type: D
• Archive: No

Table of Contents
1. General Location and Description................................................................................................. 5
1.1 Location and Description of Property..................................................................................... 5
1.2 Project Description................................................................................................................. 5
1.3 Major Drainage Basins........................................................................................................... 7
1.4 Sub-Drainage Basins............................................................................................................. 8
2. Drainage Design Criteria............................................................................................................. 11
2.1 Development Criteria Reference and Constraints................................................................ 11
2.2 Hydrological Criteria............................................................................................................. 11
2.3 Hydraulic Criteria ................................................................................................................. 11
2.4 Geotechnical Stability.......................................................................................................... 12
3. Drainage Facility Design ............................................................................................................. 13
3.1 Proposed Sub-Drainage Basins .......................................................................................... 13
3.2 Runoff Modeling................................................................................................................... 14
3.3 Diversion Channel Design ................................................................................................... 15
3.4 Diversion Channel Geotechnical Assessment .................................................................... 16
3.5 Water Quality Enhancement BMPs...................................................................................... 16
3.6 Additional Permitting Requirements..................................................................................... 16
4. Conclusions ................................................................................................................................ 17
5. Limitations................................................................................................................................... 18
6. References ................................................................................................................................. 19
Appendices
Appendix A: FEMA Flood Insurance Rate Maps..................................................................................23
Appendix B: Drainage Area Maps..........................................................................................................25
Appendix C: CDPHE General Permit COG500000 Discharges Associated with Sand & Gravel
Mining and Processing, Certification COG500320, and Stormwater Management Plan....28
Appendix D: USDA Soils Map................................................................................................................394
AppendixE: Hydrology.......................................................................................................................457
AppendixF: Hydraulics ......................................................................................................................464
Appendix G: Diversion Channel Slope Stability Analysis............................................................. 471
Appendix H: Diversion Channel Design............................................................................................483
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