The Arapahoe County Stormwater Management Manual was adopted by the Board of County Commissioners on January 30, 2007. The Stormwater Management Manual details the County’s requirements for the planning, design, construction and operation of stormwater facilities within the unincorporated areas of the County. 

Since its original adoption, revisions have been made to provide clear guidance, regulations and updates. A Revision and Update Summary of most of these changes is provided below.

For additional information, please contact the Public Works and Development Department at 720-874-6500.

• Stormwater Management Manual
  • Table of Contents, eff 6-25-21
  • Manual Revision History
• SMM Chapter 14, eff 6-25-2021
• Phase I Drainage Report Checklist
• Phase II Drainage Report Checklist
• Phase III Drainage Report Checklist
• Drainage Letter of Conformance Checklist
• Drainage Report Certification Statement
• 20/10 Calculator
• WQ Matrix – inside Cherry Creek Reservoir Basin
• WQ Matrix – outside Cherry Creek Reservoir Basin
• NPDES Permit Area Map

Control Measure Standard Details: 

• General Details
• Forebay Detalls
• Outlet Structure Details
• Extended Detention Basin (EDB)
• Modified Extended Dentention Basin (MEDB)
• Bioretention/Rain Garden (RG)
• Sand Filter (SF)
• Grass Swale (GS)
• Grass Buffer (GB)
• BMP Materials Specifications (SEMSWA)