Phoenix City Code 32C-103: Can You Wash a Parking Lot Into the Storm Drain?

The rule starts with a ban and then lists exceptions: "A person may not release to a publicly owned right-of-way, retention or detention basin, or public storm drain system any substance that is not composed entirely of stormwater, except for the following." Note the reach. A public street, gutter or alley counts, and so does a publicly owned basin, not just the grate at the curb. Our reading is that a private on-site basin isn't a safe place for wash water either: the code defines a release as disposing "into or on any land in a manner that significant materials, pollutants, or stormwater has the reasonable potential to be introduced into the public storm drain system."

The allowed list, all "provided those releases are not a significant source of pollutants," includes:

• Water line flushing and potable water sources.
• Landscape irrigation, irrigation water and lawn watering.
• Air conditioning condensation.
• Foundation drains, footing drains and crawl space pumps.
• Individual residential car washing.
• Dechlorinated swimming pool discharges.
• Street wash water.
• Uncontaminated pumped groundwater, rising groundwater, springs, and firefighting water.

Commercial pressure washing, dumpster pad rinsing, restaurant mop water and fleet washing are not on the list. Our reading: they need a city discharge permit or an AZPDES permit, or they go somewhere other than the storm system. The city's restaurant brochure says the same thing in practice: "Pour mop and wash water into the mop sink or down floor drains… NOT into gutters, alleys, parking lots or a storm drain."

• Stormwater. Rain and its runoff. Anything else mixed in makes it a non-stormwater release.
• Public storm drain system. Catch basins, curb inlets, pipes and channels that carry runoff away. It's separate from the sanitary sewer.
• Right-of-way. The street, gutter, sidewalk and alley. Hosing wash water into the gutter counts as a release even if it never reaches a grate.
• Street wash water. The code doesn't define it. Our reading is that it means washing of public streets, not a private parking lot.
• Significant source of pollutants. Even allowed water loses its pass if it carries soap, oil or debris in quantity.

Anyone who releases water in Phoenix: business owners, property managers, restaurant staff, and the pressure washing, window cleaning and mobile detailing crews they hire. Section 32C-104 adds a written stormwater management plan for anyone who "conducts an activity on nonresidential property" with a reasonable potential to affect stormwater, and the plan's required practices include "Maintenance and cleaning of storage areas, work areas, drives, parking lots, vehicles, and buildings."

This doesn't cover water that goes to the sanitary sewer through a legal connection, such as a mop sink or floor drain inside the building. That's governed by the city's sewer rules in Chapter 28, including its grease rules.

A shopping center hires a pressure washer. The crew blocks the inlets, vacuums up the wash water and hauls it off. That keeps the release out of the storm system, which is the point of the rule.

A restaurant rinses its grease bin area into the alley. The water carries grease, food scraps and cleaner into the right-of-way. That's a release of non-stormwater, and it breaks the city's own mop-water guidance.

A homeowner washing the family car in the driveway. Here the answer flips: "Individual residential car washing" is on the list. Move the same wash to a business washing its delivery vans and it isn't.

1. 1List every outdoor wash job on the property: sidewalks, drive-thru lanes, dumpster pads, loading docks, vehicles.
2. 2Route what you can to the sanitary sewer through an indoor mop sink or approved drain, with grease devices where the city requires them.
3. 3Require pressure washing contractors to capture and haul their wash water, and put that in the contract.
4. 4Write the stormwater management plan 32C-104 asks of nonresidential activities, including parking lot cleaning practices.
5. 5If a discharge can't be avoided, apply for a city permit under 32C-105. The code sets the fee at "at least $1,000.00 per year," for up to five years.
6. 6Keep grates and basins clean so what does reach them is only rain.

• "Biodegradable soap makes it fine." Not in Phoenix, whose list has no pavement or building washing at all. Chandler is the Valley exception: City Code 45-6 allows pavement washing with biodegradable soaps after hazardous materials are removed. Tempe and Paradise Valley lists don't include it either.
• "Street wash water covers the parking lot." A private lot isn't the street, in our reading.
• "The retention basin is on my property, so I can drain into it." The ban's text names publicly owned basins. A private basin that drains to a drywell or overflows to the street can still count as a release under the code's definition, so treat that as our reading and ask the city before using it.
• "The contractor is responsible, not me." The owner of record is presumed in control unless the owner shows someone else knowingly accepted responsibility, and anyone "causing or contributing to a violation" must report it and stays liable for fines. The owner and the contractor can both be on the hook.
• "A little rinse water doesn't count." The exceptions all turn on not being "a significant source of pollutants," and rinse water carries what it rinsed.

The penalty section, 32C-107, makes a violation a Class 1 misdemeanor, with a civil sanction "of not more than $2,500.00 for each violation. Each day of each violation shall constitute a separate violation."

If your floor drains and mop sink are the legal place for wash water but they're slow or backing up, HQ's commercial drain cleaning clears and cameras those lines, with free estimates.