Phoenix City Code 32C-103: Who Maintains Retention Basins and Drywells

The duty is one sentence: "A person shall maintain best management practices and post-construction stormwater controls, including but not limited to stormwater retention and detention basins, drywells, and storage structures." The same section requires records: "The owner shall keep the records for a minimum of five years from the date the record is created and shall make the records available to the City upon request."

The city's manual adds the schedule for drywells: "it shall be the owner's responsibility to clean and maintain each structure to assure that each remains in proper working order. Under no condition shall the regular maintenance schedule be greater than every three years."

The program on top of the code:

• Inventory. "Effective July 1, 2022, the City of Phoenix has started implementation of a program to inventory, track, inspect, and confirm adequate maintenance of post-construction stormwater controls for public and private projects of one acre or more."
• First inspection. "Applicable projects will undergo a site inspection within one year of construction completion."
• A written plan. Since March 1, 2024, a site-specific maintenance plan goes in with the grading and drainage or paving plans.
• Yearly self-checks. The plan template says "Annual self-monitoring of the permanent controls by the property owner or their designee is required," and the city randomly picks owners each year to return an inspection form.
• Access. Under 32C-106, denying a city representative reasonable access "is in violation of this chapter."

• Post-construction stormwater control. The code's words: "any device or feature permanently installed and designed to manage or treat stormwater, including but not limited to retention, detention, storage, infiltration, or treatment systems."
• Best management practices (BMPs). The everyday habits and fixes that keep pollutants out of stormwater: sweeping, clearing grates, fixing leaks.
• Owner or designee. The owner, or a property manager or contractor the owner assigns. The code starts by presuming the owner of record controls the property.
• Self-monitoring. The owner's own yearly inspection of the controls, written down and kept.

Any person with controls on the property: owners, property managers and tenants who run the site. The inventory, the one-year inspection and the O&M plan apply to projects of one acre or more with permanent controls whose construction application went in on or after June 30, 2022, as the city's page lists them.

Leases matter, but the city starts with the owner. Under 32C-107, the owner of record is presumed to have control "unless the owner establishes that another person has knowingly and in good faith accepted responsibility for the activity or property at issue." So a tenant who knowingly took on basin upkeep can carry the duty, but the owner has to show it, which makes the lease wording and the tenant's records the evidence.

Older sites under one acre aren't in the inventory program, but the maintenance duty in 32C-103 still applies to them.

A property manager takes over an office park. The files have the grading plans but no drywell records. The manager starts a log, books cleaning for any well without a record in the last three years, and keeps every invoice and photo for five years.

A new distribution center gets its first-year visit. The city inspects within a year of completion, checks the basin against the O&M plan, and later the owner does the yearly self-check.

A tenant signs a triple-net lease. The lease makes the tenant maintain the basin, and the tenant signs off on it knowingly. Here the answer flips: if the basin fails, the city still starts with the owner of record, but the owner can point to a tenant who "knowingly and in good faith accepted responsibility." That only works if the lease says so clearly and the tenant's cleaning records exist, so the owner asks for them every year.

1. 1Find the controls. Pull the approved grading and drainage plan and the O&M plan, if one was filed.
2. 2Start the record file now: inspection dates, photos, cleaning invoices, and what was fixed. Keep each for five years.
3. 3Clean every drywell on a schedule of three years or less, and after any storm that leaves water standing more than 36 hours.
4. 4Do the yearly self-inspection on projects in the program, and return the city's form if you're picked.
5. 5Keep the drywells in ADEQ's myDEQ inventory, and update it when the property sells.
6. 6Write the duty into leases and service contracts, knowing the city still looks to the owner.

• "The city maintains private basins." Private basins carry a stamped "No City Maintenance" sign for a reason.
• "Only new sites have to maintain anything." The inventory program is new. The maintenance duty in 32C-103 covers all controls.
• "If it drains eventually, it's fine." The standard is empty within 36 hours.
• "Records are optional." The code requires five years of them, on request.
• "The tenant is responsible, so I'm not." The city presumes the owner is in control until the owner shows a tenant knowingly accepted the duty. Without a clear lease and records, that presumption stands.

The penalty section, 32C-107, makes a violation a Class 1 misdemeanor, and "A person who violates this chapter is subject to a civil sanction of not more than $2,500.00 for each violation. Each day of each violation shall constitute a separate violation."

Drywell cleaning is specialty civil work. If the basin is fine but storm or floor drains inside the building back up, a licensed plumber can camera and jet those lines.