Pima County, AZ Environmental Rules: Stormwater Management (2026)
Key Facts
- Applies to
- Unincorporated Pima County new development
- Standard
- Storm Water Detention/Retention Manual
- Alternative
- Fee in lieu of detention, chief engineer approval
- Approving official
- Pima County chief engineer
Summary
New development in unincorporated Pima County must reduce peak or volumetric storm water runoff, using the county's Storm Water Detention/Retention Manual, unless a fee in lieu is approved.
Any new development shall provide some method of peak or volumetric runoff reduction, unless fees in lieu of detention are proposed pursuant to Section 16.48.040 and approved by the chief engineer. The amount of reduction is stipulated within the Storm Water Detention/Retention Manual. The peak runoff reduction should be provided through detention of storm water and storm water harvesting for supplemental irrigation, where possible. The Storm Water Detention/Retention Manual, approved for use by the board, or other applicable engineering standards for storm water control and/or storm water harvesting that is approved by the chief engineer shall be used for design. Any revisions to the Storm Water Retention/Detention Manual will be reviewed by the flood control district advisory committee, prior to adoption by the board as updated design standards for detention/retention. (Ord. 2010-FC5 § 1 (part), 2010; Ord. 2005 FC-2 § 2 (part), 2005; Ord. 1999 FC- 1 § 1 (part), 1999; Ord. 1988 FC-2 Art. 14 (part), 1988)
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-64: Contains Supplement, with local legislation through Ordinance 2026-9, passed 7-28-2026, current through 7-28-2026).
Full Breakdown
Any new development in the unincorporated county must provide some method of peak or volumetric runoff reduction, unless the developer proposes and the chief engineer approves fees in lieu of detention instead. The required amount of reduction follows the county's Storm Water Detention/Retention Manual, and peak runoff reduction should be achieved through storm water detention or harvesting for supplemental irrigation where possible.
Violations & Fines
Developing without providing runoff detention or an approved fee-in-lieu arrangement violates Pima County Code Chapter 16.48; the county can withhold approval of the development plan until a compliant detention or retention design is submitted.
Frequently Asked Questions
Can I pay a fee instead of building a detention basin in unincorporated Pima County?
What standard sets the required runoff reduction amount?
Sources & Official References
Other rules in Pima County
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