What can a Mesa business not put down the drain? City Code 8-4-15 prohibited discharges and limits

Subsection (A) says no person may discharge into the public sewer any of the following:

• Interference or pass-through. Wastewater that could disrupt the treatment plant or pass through it untreated.
• Clear water. Storm water, surface water, groundwater, roof runoff, subsurface drainage, single-pass cooling water or condensate that may constitute inflow, unless the City Manager or Water Resources Director approves it.
• Fire and explosion hazards. Pollutants with a closed cup flashpoint below 140 degrees F, or that push the sewer past 10 percent of the Lower Explosive Limit on any single reading.
• Solids and grease. Solid or viscous pollutants, animal fats, oils and grease, petroleum oil or nonbiodegradable cutting oil "in amounts that will cause" interference, pass-through or obstruction.
• Toxic or corrosive waters. Substances that injure the plant, cause corrosive structural damage, endanger people or produce toxic gases that threaten workers.
• pH. Below 5.0 or above 10.5 standard units.
• Heat. Above 150 degrees F, or in amounts that inhibit biological treatment. In no case may the temperature at the plant headworks exceed 104 degrees F.
• Dilution. Wastewater diluted in place of pretreatment to meet a standard.
• Hazardous waste. A non-domestic discharge with a hazardous waste characteristic, unless the city approves it in writing on request.
• Named chemicals. Benzene above 35 micrograms per liter and chloroform above 2,000 in a grab sample, and zero for DDT, DDE, aldrin, lindane, heptachlor, PCBs and similar compounds.

Subsection (B) adds daily average limits for Class I industrial users, and for a Class II user the city names in writing: arsenic 0.13, cadmium 0.047, copper 1.5, cyanide 2.0, lead 0.41, mercury 0.0023, selenium 0.10, silver 1.2 and zinc 3.5 milligrams per liter. Subsections (C) through (E) add city-set limits, best management practices and mass limits set in permits.

• POTW. The publicly owned treatment works, the city's sewers and treatment plants.
• Interference and pass-through. Disrupting the plant's process, or letting pollutants through it.
• Closed cup flashpoint. The temperature at which a liquid's vapors can ignite in a lab test. Lower means more flammable.
• Class I, II, III. Mesa's industrial user classes. See the discharge permit page.

Every person discharging to Mesa's sewer, not only factories. The clear-water, temperature, pH and grease rules reach restaurants, car washes and any commercial building. The metal limits in (B) apply to Class I users, and to a Class II user only after a written city determination.

A steam kettle line. A kitchen drains hot condensate to the sewer. The limit is 150 degrees F at the point of entry, so the designer looks at cooling or tempering that flow before it leaves the building.

A car wash. If a cleaning product drives the wastewater below pH 5.0, the discharge is prohibited no matter how small the site is.

The edge case. A shop discharges very little, but one batch dumps a solvent with a low flashpoint. The rule says "in no case," with no minimum volume.

1. 1Walk the building's drains and list what each one receives: hot water, steam condensate, cooling water, rinses, oils.
2. 2Check temperature and pH against the 150 degrees F and 5.0 to 10.5 limits.
3. 3Send roof, cooling or condensate flows to an approved outlet, or ask the city for written approval.
4. 4If you are in a regulated class, get the permit and its limits. See the discharge permit page.
5. 5For a kitchen, size and maintain the grease interceptor.

• "Only industrial sites are covered." Subsection (A) says "no person."
• "Hot water is harmless." Above 150 degrees F it is prohibited.
• "The grease rule has a number." Mesa's text ties it to obstruction and interference, not a concentration.
• "Chandler's pH limit applies." Mesa's window is 5.0 to 10.5.