Stormwater Detention-Retention

The Pima County Regional Flood Control District has prepared the manual: Design Standards for Stormwater Detention and Retention (Manual) to supersede the Pima County/City of Tucson Stormwater Detention/Retention Manual. The Manual contains some substantive changes, including replacement of the threshold retention requirement with a first flush retention requirement (retaining the first 0.5 inches of rainfall), introduction of the use of integrated site planning and other Low Impact Development practices, description of acceptable methodology for hydrologic and hydraulic analysis, more specific design standards, and a description of  inspection and maintenance responsibilities for detention and retention facilities.

• Design Standards for Stormwater Detention and Retention Manual - Board Version (November 2015)
• Appendix A - First Flush Retention
• Appendix B - Example LID Peak Discharge Calculations
• Appendix C - Stormwater Harvesting Memorandum
• Appendix D - The Method Used by the SWH Spreadsheet
• Appendix E - Details
• Appendix F - Maintenance Checklist
• Appendix G - Covenants
• Appendix H - Hydrograph Rise Time

Stormwater Detention/Retention Manual History

Prior to the 2015 manual, the District regulated stormwater detention/retention through the Stormwater Detention/Retention Manual developed in coordination with the City of Tucson. The revision process involved an extensive literature review to establish modern best practices. Proposed revisions were reviewed by the Flood Control District Advisory Committee and the development community prior to adoption. The latest revision was adopted by the Board of Supervisors on December 15, 2015.