Industrial Pretreatment Program

Helping businesses capture pollutants at the source to protect people, wastewater infrastructure, and the environment.

Working with Business

The Wastewater Department is charged with making sure that harmful substances aren't discharged into our sewer system. Our Industrial Pretreatment Program is set up to talk to businesses and identify things that can be a problem.

The City has a Pretreatment Ordinance that allows us to condition or deny businesses from discharging some substances into the sanitary sewer—substances that create safety hazards, damage structures, interfere with treatment plant operations and processes, or that can't be removed and pass through into biosolids or with the effluent into the Spokane River.

The Pretreatment Program's first step is to survey businesses to determine whether they have the potential to discharge anything other than domestic wastewater. The information gathered by the survey is used to determine what the business has to do and informs us about what is in the wastewater system. We can also help businesses to avoid any accidental spills. The information is also reported annually to the Washington State Department of Ecology.

Business owners should understand the regulations that apply to their wastewater discharge, and comply with applicable regulations and standards. Let's take a look at what's required.

Domestic Dischargers

Businesses that discharge wastewater only from restrooms or hand sinks are considered Domestic Dischargers. They are responsible for ensuring that no Prohibited Discharges are introduced to the sewer system from their facility. This level of normal domestic use is not regulated.

Minor Industrial Users

Businesses that discharge wastewater containing nondomestic pollutants must abide by Prohibited Discharge Standards and follow industry-specific Best Management Practices (BMPs) to keep their wastewater as clean as reasonably possible.

BMPs can prevent the release of pollutants that can damage the sewers or the treatment plant, cause the plant to release pollutants that violate its Permit, or endanger wastewater personnel.

For example, restaurants that do not properly maintain their grease interceptors can cause grease clogs in the sewer resulting in sewer backups into streets or basements; auto repair shops that do not properly dispose of used solvents can cause an explosion hazard in the sewer or at the plant headworks; and car wash operations that use acidic cleaners and do not properly neutralize their wastewater prior to discharge can cause acid damage to the sewers.

Significant Industrial Users

The City of Spokane requires all Significant Industrial Users to obtain a Wastewater Discharge Permit.

A Significant Industrial User is:

  1. A user subject to categorical pretreatment standards as defined by the US Environmental Protection Agency. These processes by their nature generate pollutants that, if unregulated, can disrupt treatment processes, pass through the plant unchanged and pollute the river, or create hazardous conditions in the sewer or treatment plant.
  2. A user that:
    1. Discharges an average of 25,000 gallons per day or more of process wastewater to the sewer (excluding sanitary, noncontact cooling and boiler blow down wastewater); or
    2. Contributes a process waste stream which makes up 5 percent or more of the average dry weather hydraulic or organic capacity of our treatment plant. “Organic capacity” means the capacity of the treatment plant to treat wastewater as opposed to the “hydraulic capacity” or capability to accept and handle fluids; or
    3. Is designated as such by the plant's superintendent because it has a reasonable potential to cause an adverse effect on the plant's operation, adverse impact on the City's ability to comply with its operating permit, cause the plant to violate any pretreatment standard or requirement, or because of other regulatory control needs. (Source: 40 CFR §403.3(v))

Pretreatment program staff scientists inspect such permitted businesses, sample their wastewater discharges, and work with them to protect the environment, the wastewater treatment plant, and personnel.

Direct Dischargers

Any industry that discharges wastewater directly to a river or other surface water (Direct Dischargers) must apply for and comply with a Discharge Permit from the Washington State Department of Ecology.

Fats, Oils & Grease

Fats, Oils, and Grease (FOG) are a problem for our sewer system. Fats and greasy waste from commercial kitchens can build up and cause problems, including unpleasant blockages and backups. Oily vehicle fluids from car washing and auto repair are harmful to aquatic life. Both types of FOG should stay away from drains.

Food Service FOG

Here are some simple ways to reduce the amount of food grease going down your drains:

What about grease traps and interceptors?

Grease traps and interceptors are pretreatment devices that capture fats, oils, and grease in wastewater before it enters the sewer. These devices are required in all commercial kitchens due to the critical role they have in preventing costly problems in your pipes and in the sewer. However, these devices can’t do the job alone. Owners and managers of commercial kitchens are responsible for correctly installing, operating, and maintaining their grease control devices. The documents below outline the City of Spokane’s rules, and will help your kitchen run smoothly.

Grease Trap Maintenance
Grease Interceptor Maintenance
Grease Control Device Recordkeeping
Grease Control Device Maintenance Log
Grease Control Device Prohibitions

If your kitchen does not have a grease control device, please call 311 and they will connect you with Business Development Services for free assistance. If you are calling from outside City limits, please call 509.755.2489.

Petroleum Product FOG

The following wastewater Best Management Practices are required to keep petroleum oils out of storm drains and sewer pipes:

  • Determine whether each waste material is hazardous by using the guidelines in WAC 173-303-9903 and WAC 173-303-9904.
  • Post signs above drains and sinks prohibiting the discharge of chemicals and oils.
  • Never allow wash water or any other liquids to enter the street, gutter, storm drains, or dry wells.
  • Replace leaking containers.
  • Dry sweep floors before mopping or hosing down.
  • Install secondary containment for all liquid storage capable of holding 110% of the largest possible spill.
  • Develop a written spill response plan, keep a spill kit on site, and train employees on proper clean up and disposal.
What about oil/water separators and sand traps?

Oil/water separators are pretreatment devices that capture sediment and oils from wastewater before it enters the sewer. These devices are required by any commercial facility that could have petroleum in their wastewater. Owners and managers of these facilities are responsible for installing, operating and maintaining their oil/water separators in accordance with the City of Spokane’s rules in the fact sheet below:

Dental Wastewater

Dental Wastewater Discharges

Dental practices that discharge waste material into the City of Spokane sanitary sewer system must be in compliance with the City's discharge limits and Environmental Protection Agency (EPA) regulations.

On July 14, 2017, the EPA promulgated new regulations for dental offices in the Code of Federal Regulations, 40 CFR Part 441. Dentists must:

  • Install an amalgam separator(s) that meets the requirements in the Approved Amalgam Separator document, and maintain it according to the manufacturer's recommendations
  • Follow the required policies in the Dental Office Best Management Practices (PDF 307 KB)
  • Submit a One-time Compliance Report to the City of Spokane Industrial Pretreatment Program:
    • By 10/12/2020 for existing offices
    • Within 90 days if the office is new or transferred to a new owner after July 14, 2017

Who needs to submit a compliance report?

All dental practices, both exempt and non-exempt, must submit a One-Time Compliance Report.

Disposal of mercury amalgam

Information about the safe disposal of materials containing mercury may be found at:

Update your practice's contact information

Is yours a new dental office - or have you recently relocated your office within the City of Spokane Wastewater Treatment Facility service area? Please contact us at 509.625.4600 so we can determine whether or not you must submit a One-time Compliance Report.

The Industrial Pretreatment Program staff know that this new reporting process is complex. Please contact us at 509.625.4600 if you have questions and we will be happy to assist you.

SMC Update

Documents for Public Comment

  • No documents for public comment at this time.

Documents for Businesses

Best Management Practices

Wastewater Surveys

Contact Information


Industrial Pretreatment Program
Riverside Park Water Reclamation Facility
4401 N. Aubrey L. White Parkway
Spokane, WA 99205-3939

Office Hours:
Monday – Friday 7:30 a.m. to 4 p.m.

Report Spills to Sewer Immediately
509.625.4600 and 509.625.7900

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