Chandler, AZ Environmental Rules: Stormwater Management (2026)
Key Facts
- Max retention basin depth
- 3 ft in a 100-yr, 2-hr storm
- Max side slope
- 4:1 horizontal to vertical
- Drainage deadline
- 36 hours after a storm event
- Design standard adopted
- 2023 Engineering & Design Standards Manual
- Violation penalty
- Civil infraction under Code § 1-8.7
Summary
Chandler requires new development to submit a stormwater retention plan and adopts Maricopa County drainage standards by reference. Retention basins must limit water depth to 3 feet in a 100-year, 2-hour storm, keep side slopes no steeper than 4:1, and fully drain within 36 hours under City Code Section 45-3.
45-3.B. All retention basins shall have a design capacity such that water depth is limited to a maximum of three (3) feet resulting from a one hundred-year, two-hour storm. The City Engineer may approve a greater water depth when a positive method of water disposal, such as pumping facilities, is available and under the control of the City or another governmental agency. The depth of the basin shall be measured from the basin's low outfall point. Side slopes shall not be steeper than 4:1 (horizontal: vertical)... 45-3.F. All stormwater must be evacuated from a parcel through means of percolation on site within thirty-six (36) hours of a storm event. Drywells are permitted to drain surface retention areas only when no other means of disposal is available.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 79).
Full Breakdown
Chapter 45 of the Chandler City Code, entirely rewritten by Ordinance No. G. A requires a conceptual stormwater collection and retention plan with any preliminary plat, construction plan or site development plan, showing the collection method, retention basin depth and side slopes, retention calculations, high-water elevation, outfall point, and the disposal method within thirty-six hours. B caps retention basin water depth at three feet for a one-hundred-year, two-hour storm, measured from the basin's low outfall point, and limits side slopes to no steeper than 4:1 horizontal-to-vertical, though the City Engineer can approve a deeper basin where pumping facilities exist or a gentler slope departure for an innovative, safe design.
F requires that water to fully evacuate through on-site percolation within thirty-six hours, with drywells permitted only when no other disposal method is available. E. Section 45-4 separately lets the City drain, at the owner's expense, any privately owned retention basin left standing more than thirty-six hours.
Violations & Fines
Standing water left in a private retention basin beyond thirty-six hours lets the City enter and drain it at the owner's expense under Section 45-4, with costs assessed as a lien on the property if unpaid under Sections 45-4.1-45-4.4. Failing to maintain or altering a stormwater system so it no longer functions as engineered is a declared public nuisance under Section 45-5 and a civil infraction under Section 45-10.B, escalating to a misdemeanor for willful or negligent violations under Section 45-10.C.
Frequently Asked Questions
How deep can a Chandler retention basin get during a storm?
Do I need a drainage plan to build in Chandler?
What happens if my retention basin does not drain?
Sources & Official References
Other rules in Chandler
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Stormwater Management in Nearby Cities
How other cities in Maricopa County handle stormwater management.