Can you hose a dumpster pad into the storm drain?

Storm drains are made for rain. Chandler's stormwater page says the goal is to make sure only rain is in the storm drain. It also explains that storm systems generally do not treat water before it is discharged. What goes in comes out at a retention basin, a wash or a park, and pollutants like oil and grease can stick to the pipes on the way.

Sanitary sewers work the other way. They carry wastewater from sinks, floor drains and other fixtures to a treatment plant. Wash water from a dumpster pad belongs on that side, and only through a route the city allows. If the difference is new to you, do storm drains and sanitary sewers connect explains how the two networks are kept apart.

Your lot's own catch basins, retention basins and drywells are part of the same problem. Dirty water that goes down a private grate does not disappear. It travels to the structures downstream, adds sediment and grease, and can clog them. Sediment and grease can cut into a drywell's ability to drain. See can a plugged drywell be cleaned or replaced for what happens when one plugs.

Phoenix is the clearest example in the Valley, and the same idea appears in most cities. The rule is in City Code 32C-103.

• 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 a short list of exceptions.
• The exceptions include releases under a discharge permit, emergency firefighting, and a list that covers water line flushing, landscape irrigation, air conditioning condensation, individual residential car washing, dechlorinated swimming pool discharges and street wash water.
• Commercial wash water from a dumpster pad, a loading area or a lot cleaning job does not appear on that list. Treat it as prohibited unless the city tells you otherwise in writing.
• A person also may not install or use a direct connection to the public storm drain system without written permission from the City Manager.

The list is written for the public storm drain system, and it also covers publicly owned retention and detention basins. A private lot drain often leads to a private basin, so the wording does not fit every case. But it usually connects to a public system somewhere, and the safe assumption is the same: only stormwater goes in. Ask your city if you are unsure where your lot drain ends up.

### What a violation can mean

City Code 32C-107 says a violation of the chapter is a Class 1 misdemeanor and each day is a separate offense. It also allows a civil sanction for each violation, with each day counted separately. The code also says the owner of record of the property where a violation occurs is presumed to be the person with control, unless the owner shows that someone else knowingly and in good faith accepted responsibility.

That last point matters for landlords. If a tenant's cleaning crew washes a pad into a grate, the owner may be the first name the city looks at. It is worth adding a line about wash water to your vendor contracts and lease rules. See who is responsible for parking lot drainage for how leases usually divide the work.

Scottsdale's water quality guidance for pressure washing is a good model, since it lays out the steps. The same ideas apply almost anywhere in the Valley.

1. 1Plan the disposal first. Decide how you will contain the wash water and where it will go before you start. Get permission to use the disposal point.
2. 2Block the storm drains. Use gravel bags or berms, or seal the drain with plugs or rubber mats. Berms may not work well when the drain sits at the bottom of a slope or there is a lot of water.
3. 3Pre-clean. Sweep up trash and dirt before you wet wash. Use dry methods and absorbents on small oil spots.
4. 4Use less water. A low-volume nozzle and cleaning products without hazardous substances make the wash water easier to handle.
5. 5Collect all of it. Use an approved containment method. Wet/dry vacuums, sump pumps and vacuum pumps can pull wash water up after the job. Scottsdale adds that wash water with high pollutant concentrations, including cleaning compounds, must be fully collected and may not be left to evaporate.
6. 6Dispose of it properly.

### Where the wash water can go

Scottsdale lists two ways to dispose of collected wash water:

• Through a pretreatment device. Discharge to the sanitary sewer through a fats, oils and grease interceptor or a petroleum, oil and grease interceptor. Scottsdale says the easiest access point is the business mop sink, or the cleanout located before the interceptor.
• By a liquid waste hauler. A permitted third-party company takes the water to a treatment site. Scottsdale says the hauler must be permitted by the Arizona Department of Environmental Quality to manage wastewater.

Not every city accepts every method, and your building may not have an interceptor. Mesa's code, for example, bars storm water and surface water from the sanitary sewer unless the city approves it, and it lists other prohibited substances as well. So call your city's stormwater or pretreatment office before you plan a wash-down routine. For the sewer-side rules on interceptors, see does a loading dock drain need an oil and grease separator.

Some dumpster pads have their own drain plumbed to the sanitary sewer. If yours does, that may be the intended disposal path for wash water, but check your site plans and confirm with the city. Do not assume the pad drain and the parking lot grate lead to the same place.

If a crew washed into a drain by mistake, act quickly and keep it factual.

• Stop the water and block the inlet.
• Collect what you can with a vacuum or absorbent pads.
• Write down what was washed, the date, the amount and the drain location.
• Have the catch basin sump cleaned and ask how the material will be disposed of. See what a catch basin is and how often to clean it.
• Call the city's stormwater program if the release was large or included chemicals.

Treat the storm drain like a rain-only line. Wash pads with the drain blocked, collect the water, and send it to an approved sanitary point or a permitted hauler. If the site is a warehouse or industrial yard, ask whether state industrial stormwater rules also apply, which is covered in do I need a stormwater permit for a warehouse or loading dock. Put that in writing for your janitorial and pressure washing vendors. It takes a few minutes of planning and avoids a city notice that lands on the property owner.