Maricopa County, AZ Environmental Rules: Stormwater Management (2026)
Key Facts
- Enforcing agency
- County Drainage Administrator (Planning & Development)
- Clearance exemption
- Buildings 200 sq ft or less
- Design standard
- 100-year storm event required
- On-lot retention
- Barred on residential lots under 1 acre
- Appeal deadline
- 30 days to Drainage Review Board
Summary
Grading and drainage plans need Drainage Administrator clearance before development in unincorporated Maricopa County; buildings 200 square feet or smaller and non-fixed pipe-rail fencing are exempt unless sited in a retention basin or drainage way.
Provided no development is to be located within a retention basin or drainage way, a drainage clearance shall not be required for: (i) any building with an area of 200 square feet or less, or (ii) for pipe rail type fencing that is not permanently affixed to the ground.
Full Breakdown
Maricopa County's Drainage Administrator, the Planning and Development Department director or a designee, reviews and approves grading and drainage plans for entitlements and development in unincorporated areas under MCZO § 905. A drainage clearance is required before development proceeds, with a final clearance inspection needed before certificate of occupancy. Buildings of 200 square feet or less and unattached pipe-rail fencing are exempt, unless located in a retention basin or drainage way. Residential lots under one acre cannot use on-lot retention. Drainage systems must be engineered to the 100-year storm event and cannot increase peak discharge onto neighboring property; violations bring notices of non-compliance recorded against the property title.
Violations & Fines
Developing without required drainage clearance lets the Drainage Administrator record a notice of non-compliance against the property's title, order removal of improvements, and pursue compliance action; appeals go to the Drainage Review Board within 30 days.
Frequently Asked Questions
Do I need a drainage clearance to build a shed in unincorporated Maricopa County?
Can I put a retention basin on a small residential lot?
Sources & Official References
Other rules in Maricopa County
Compare Maricopa County to another location·View the Arizona environmental rules overview
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