Stormwater Design Standards

Larimer County have adopted the Larimer County Stormwater Design Standards, effective September 1, 2023 . These standards apply to the design and construction of stormwater facilities within unincorporated Larimer County.

The Board of County Commissioners adopted the new Standards on August 14, 2023.

Larimer County Stormwater Design Standards (2023)

• Full Manual & Appendices - 2024
• Appendices Only - 2024

Mile High Flood District (MHFD) Manual

• MHFD Manual, Volume 1: Management, Hydrology, and Hydraulics
• MHFD Manual, Volume 2: Structures, Storage, and Recreation
• MHFD Manual, Volume 3: Stormwater Best Management Practices (BMPs)

Larimer County Stormwater Design Standards By Section

• Cover & Table of Contents
• Chapter 1 - General Provisions
• Chapter 2 - Drainage Report Submittal Requirements
• Chapter 3 - Drainage Principles & Policies
• Chapter 4 - Floodplains
• Chapter 5 - Rainfall
• Chapter 6 - Runoff
• Chapter 7 - Streets
• Chapter 8 - Inlets
• Chapter 9 - Storm Drains
• Chapter 10 - Culverts
• Chapter 11 - Bridges
• Chapter 12 - Open Channels
• Chapter 13 - Hydraulic Structures
• Chapter 14 - Detention (Storage)
• Chapter 15 - Post-Construction Stormwater Controls
• Chapter 16 - Construction Stormwater Management
• Chapter 17 - Revegetation

Appendices

• Appendix A - Submittals Checklist
• Appendix B - CSM Guidance Document
• Appendix C - CSM ESCP Checklist
• Appendix D - CSM Standard Forms
• Appendix E - CSM Construction Symbols
• Appendix F - CSM Standard Notes
• Appendix G - CSM Erosion Control
• Appendix H - CSM Sediment Control
• Appendix I - CSM Materials Management
• Appendix J - CSM Site Management
• Appendix K - Seed Mixes for Revegetation

*CSM = Construction Stormwater Management

Previous Versions

• Larimer County Stormwater Design Standards (2005)

Resolution

• Resolution Adopting the Larimer County Stormwater Design Standards