When does a Gilbert business have to pretreat its wastewater? Town Code 66-234

Subsection (a) lists the instances in which "pretreatment will be required," and says the director shall give the permit applicant the pretreatment levels that must be reached:

1. 1When the director finds, on the initial permit application, that the proposed industrial waste must be pretreated to lower any component of the discharge.
2. 2When the town must improve the discharge from its wastewater treatment plant. The director then requires a permit holder to install or enlarge pretreatment facilities to lower the affected component.
3. 3When any wastewater prohibited under the article is produced. The producer pretreats to the extent required, before discharging to any town sewer.
4. 4The director reviews whether a pretreatment method is acceptable, on sound engineering and operational evaluations.
5. 5Pretreatment facilities are always subject to inspection by the director, or to a joint inspection by the director and the Cities of Phoenix or Mesa.
6. 6When plant expansion or changes in operations increase a permittee's strength or volume of discharge, the director may require additional pretreatment, unless the permittee previously made industrial cost recovery payments for reservation of additional industrial capacity.

The same subsection puts the cost on the permit holder and adds a paperwork duty: the owner keeps written records of all cleaning, repair, calibration and maintenance, at the facility, for at least three years, and gives them to the director on request.

The rest of the section sets the process. Sludge removed by the pretreatment facility is disposed of under federal, state and local law (b). Dilution or commingling as a partial or complete substitute for adequate treatment is prohibited (c). Detailed plans go to the director for approval before construction, and later significant changes to the approved facilities or operation must be reported and approved (d). Once plans are approved and a permit issued, the plans are placed on file with the director in permanent, reproducible form, without cost to the town, before a building permit will be issued (e). Pretreatment facilities must obey a demand to halt a discharge immediately when the director gives notice of imminent endangerment or interference with the treatment works (f). Tampering with monitoring or sampling equipment to alter readings is unlawful (g).

• Pretreatment: reducing or eliminating pollutants, or changing their nature, before they enter the town's treatment works, by physical, chemical or biological processes, process changes or best management practices.
• Pretreatment device: the town's list includes grease removal devices, oil interceptors, sand and grit interceptors, solids traps, lint traps, metal recovery units, hair traps, silver recovery systems and acid neutralization tanks.
• Director: the director of the department of public works or the director's designee.
• Wastewater the article prohibits: the list is in 66-231(b), and it includes water hotter than 150 degrees Fahrenheit, and animal fats, oil and grease in amounts capable of obstructing the sewer.
• Commingling: not defined in 66-234. Our reading is mixing a strong stream with a clean one so that the combined sample looks better.

Permit applicants and permit holders under the industrial permit sections, and any producer of wastewater the article prohibits. A user outside all three has no subsection (a) trigger.

Grease removal devices, parts-washing and vehicle bay pretreatment are driven by other sections. Where a pretreatment device is installed, 66-243(d) separately requires the owner or operator to maintain it at their expense, keep it easy to reach and keep the same three years of records.

A new production facility applying for a Class A permit. The director sets the pretreatment levels. The engineer draws the tank and treatment equipment, the director approves the plans, and the permit issues. Then a reproducible plan set goes on file with the director before the building permit.

A plant expands. The new line raises the volume of its discharge, so the director may require more pretreatment. If the plant earlier paid industrial cost recovery to reserve that capacity, the unless clause in subsection (a)(6) applies. The answer flips on the payment history.

The edge case: a plant mixes its strong stream with clean cooling water before sampling. That is commingling as a substitute for treatment. Subsection (c) prohibits it, and 66-231(b)(15) bars unpolluted process water and cooling water unless the director approves it.

1. 1Ask the town for the pretreatment levels that apply. The code says the director submits them to the permit applicant. Call the Town of Gilbert at (480) 503-6000 and ask for Public Works.
2. 2Have the plans for every pretreatment facility drawn in detail, and send them to the director for approval before any construction.
3. 3When the permit issues, file the approved plans with the director in permanent, reproducible form before you apply for the building permit.
4. 4Apply for the building permit through the One Stop Shop portal (OneStopShop.gilbertaz.gov), or call Development Services at (480) 503-6700.
5. 5Report any significant change to the approved facilities or how you run them, and wait for approval.
6. 6Start the maintenance log on day one and keep it at the facility.

• Plan review by the director means we comply. Subsection (d) says the review does not relieve the permit holder of responsibility for modifying and operating the facilities to produce a compliant effluent.
• The building permit comes first. Subsection (e) puts the plans on file with the director before a building permit will be issued.
• Keeping records off site is fine. Subsection (a)(6) says the records are kept at the facility.
• Mixing waste streams is a cheap fix. Subsection (c) prohibits dilution and commingling as a substitute for adequate treatment.

Gilbert's own text governs; this page explains it.