Grease Trap Regulations in Montana

Overview of Montana FOG Compliance Framework

Commercial food service businesses in Montana must control fats, oils, and grease (FOG) sent to city sewers. Montana never asked to run the federal pretreatment program itself. So EPA Region 8 acts as the Approval Authority. Day-to-day enforcement runs through each city's Publicly Owned Treatment Works (POTW).

That split structure means a restaurant, bakery, school cafeteria, or hospital kitchen reports first to a local Authority Having Jurisdiction (AHJ). That AHJ is usually Billings, Missoula, Great Falls, Bozeman, or Helena. Each city writes its own grease interceptor ordinance. Each one sets local discharge limits, issues wastewater permits, and runs inspections. The Montana Department of Environmental Quality (DEQ) then regulates the water leaving each treatment plant. DEQ does this through the Montana Pollutant Discharge Elimination System (MPDES) permit issued to the POTW. The Bozeman Water Reclamation Facility publishes its limits this way.

An operator opening or remodeling a kitchen in Montana has three rule sets to meet at once. The first is the federal ban on harmful discharges under 40 CFR Part 403. The second is the city sewer-use ordinance. The third is the model plumbing code used to install and size equipment. Miss any one and your service can stop. You can also get a notice of violation. Costs climb fast.

Governing Authorities

The Montana Department of Environmental Quality is the lead state agency for water. Its Water Protection Bureau runs the MPDES program for direct discharges to streams and rivers. That means DEQ writes and enforces the discharge permits city treatment plants must hold. But the agency does not regulate kitchens that send waste into those plants. Indirect dischargers like restaurants answer to EPA Region 8 and to each city's pretreatment program.

At the federal level, EPA Region 8 serves as the pretreatment Approval Authority for Montana. The agency reviews and approves local pretreatment programs and steps in when local action falls short.

At the city level, the following authorities run FOG control programs:

• City of Billings — Public Works Department, Water Reclamation Facility: Billings runs an Industrial Pretreatment Program. It is codified in Billings Municipal City Code Article 26-600. The Director of Public Works and approved staff can issue discharge permits, run site checks, and review pretreatment equipment specs.
• City of Missoula — Public Works & Mobility Department: Missoula's program is led by a Lab/Pretreatment Manager. It is grounded in Missoula Municipal Code Title 13, Chapter 13.07. The city's FOG Sector Control Program (Appendix 5-B) spells out the day-to-day rules.
• City of Great Falls — Public Works Department, Environmental Division: Great Falls regulates fats, oils, and grease under the Official Code of the City of Great Falls (OCCGF) Title 13, Chapter 12. Ordinance 3113 updated those rules. Kitchens must install grease control equipment, keep it working, and store service records on-site. The city FOG program brochure spells this out.
• City of Bozeman — Water Reclamation Facility: Bozeman runs an EPA/State-approved industrial pretreatment program under Bozeman Municipal Code Chapter 40, Article 3. The city updates this code to track federal pretreatment rules.
• City of Helena — Public Works Department, Wastewater Treatment Division: Helena enforces grease interceptor rules under Industrial Wastewater Regulations (Helena Municipal Code Title 6, Chapter 4). Pretreatment staff inspect Grease Removal Devices on site. The city FOG program brochure describes the visits.

Any food service kitchen outside these five cities should call the local water/sewer department or county sanitarian. Confirm which sewer-use ordinance applies and whether you need a pretreatment permit.

Installation and Sizing Requirements

Montana cities use the model plumbing codes for grease interceptor sizing and installation. The City of Billings, for example, lists the Uniform Plumbing Code, 2018 Edition in its adopted codes. Most other Montana cities also follow the Uniform Plumbing Code (UPC), published by the International Association of Plumbing and Mechanical Officials.

The UPC recognizes two types of interceptors. Hydromechanical grease interceptors (HGIs) are smaller indoor units. Gravity grease interceptors (GGIs) are the larger outdoor vaults used by busier kitchens. Sizing follows two methods drawn straight from the code:

• Flow rate (HGI) method: HGIs are sized in gallons per minute. Per UPC §1014.2.1, no HGI may have an approved flow rate above 50 gpm or below 20 gpm unless the AHJ approves it. The fixture capacity feeding the unit may not exceed 2.5 times the certified gpm rating.
• Drainage Fixture Unit (GGI) method: Gravity interceptor volume is picked from UPC Table 1014.3.6 based on Drainage Fixture Units (DFUs). When DFUs are not known, the unit must be sized to the max DFU capacity of the inlet pipe. Common floor values: 500 gallons (8 DFUs), 750 gallons (21 DFUs), 1,000 gallons (35 DFUs), and 1,250 gallons (90 DFUs).

The UPC also requires gravity interceptors to sit outside the building unless the AHJ approves an indoor location, per UPC §1014.3.4. Outdoor placement cuts sewer-gas exposure and reduces contamination risk during pumping.

Montana cities do not usually publish their own gallon-by-gallon minimums. Designers submit grease interceptor specs during building-permit and pretreatment-permit review. Helena's Industrial Wastewater Regulations require pretreatment equipment to be reviewed before occupancy. Helena Ordinance 3265 sets that rule. Bozeman's pretreatment ordinance also requires plan review for new and remodeled food sites. Check with the local AHJ before you order a unit. Interceptor size affects sewer fees and the cleaning cadence the city sets on the permit.

Cleaning and Maintenance Frequency

Montana's standard rule for grease interceptor upkeep is the "25% Rule." Pump the device before the combined volume of floating grease and settled solids passes 25% of the unit's total liquid capacity. The City of Helena puts this in writing in its FOG program brochure. It tells operators to "Keep GRDs at less than 25% full of grease and debris." Missoula uses the same threshold in its FOG Sector Control Program.

How often you must pump depends on your kitchen's grease output and the size of your unit, not on a single statewide interval. Helena's program is the most explicit. It tells operators to clean indoor hydromechanical traps weekly. It also tells them to clean exterior gravity grease vaults at least every six months, or sooner if the 25% threshold is reached, per the Helena FOG brochure. Other Montana cities set the interval through the wastewater discharge permit or pretreatment agreement they issue to each kitchen. So two restaurants on the same block can have different schedules.

The 25% Rule lines up with national guidance. Standard FOG management notes summarized by the Massachusetts Health Officers Association say a grease trap must be checked monthly. It must be cleaned by a licensed septic hauler when grease reaches 25% of the trap's effective depth, or at least every three months. That gives you a default interval where no city sets a cadence.

A state-licensed septic pumper or grease hauler must do the pumping. Pumped waste must go to an approved receiving facility. That is usually the city treatment plant headworks or a permitted disposal site. The Billings Public Works wastewater overview notes the rule. Decanting (pouring skimmed water back into the trap), partial pumping, and sending removed waste to storm drains are all banned in every Montana city.

Routine maintenance should also include checks of inlet and outlet baffles, access covers, and connected piping. Crews must remove all floating grease and settled solids during pumping. Damaged covers, gaskets, or structural defects should be repaired right away.

Record-Keeping and Manifest Requirements

Records are the backbone of pretreatment enforcement. Under 40 CFR §403.12(o)(2), Industrial Users in the National Pretreatment Program must keep monitoring records for at least three years. That period extends during any open lawsuit tied to the user's discharge or the POTW program. Montana cities use this three-year baseline as the floor.

Billings follows the Montana Local Government Records Retention Schedule and the federal three-year minimum for industrial-user logs. Great Falls, under its FOG program, requires kitchens to keep records of servicing, pumped volumes, and repairs on-site. Inspectors can review them during business hours. Missoula's FOG Sector Control Program (Appendix 5-B) tells users to keep an updated logbook of grease control activities. The Superintendent can ask for it at any time.

The records most often required are:

• Pumping manifests or service reports: One document for each service event with the date, volume of waste removed, condition of the device, and disposal location. The hauler usually signs the manifest along with someone from the kitchen.
• Maintenance logs: A running record of cleaning dates, hauler company name, and any repairs or changes to the grease removal system.
• Disposal receipts: Proof that pumped waste was delivered to an approved receiving facility.
• Inspection reports: Copies of any city pretreatment inspection reports, with deficiencies noted and corrective actions taken.

Records should be ready right away when a city pretreatment inspector arrives. Falsifying records, destroying manifests, or giving false information can be treated as a separate violation. That comes on top of the original maintenance failure and can lead to permit suspension under the city's discharge-permit conditions.

Fines and Penalties

Local FOG violations in Montana are usually treated as municipal civil infractions. Penalties are set by city administrative citation schedules, not by a single statewide table. Each Montana city's grease ordinance is enforced through the same step-by-step process the city uses for other sewer-use violations: written notice, administrative citation, compliance order, and, in the worst case, suspension or revocation of the wastewater discharge permit.

State law sets the dollar cap for an initial municipal civil infraction. Under Montana Code Annotated § 7-1-4150, the penalty is not more than $300 per violation. For a repeat offense, the cap is $500. Each city sets specific dollar amounts within those caps in its citation schedule. Ask the local pretreatment program for the current schedule. Do not rely on figures published elsewhere.

Beyond the municipal infraction process, several distinct exposures exist:

• Cost recovery for sanitary sewer overflows: If FOG from a kitchen causes a blockage that leads to a sanitary sewer overflow, the city can bill the responsible party for emergency response, cleanup, and pipe repairs. That cost comes on top of any administrative penalty. The EPA's 2004 Report to Congress on CSOs and SSOs (EPA-833-R-04-001) found blockages caused 74% of SSOs and grease caused 47% of those blockages. Montana cities use this data to back up cost-recovery claims.
• State environmental enforcement: If a discharge causes a documented release into the environment, the Montana DEQ may pursue its own enforcement under the Montana Water Quality Act. That action can run on top of any city case.
• Federal enforcement under the National Pretreatment Program: EPA Region 8 is the Approval Authority. It can act directly against a Montana industrial user when local enforcement is too weak. That includes breaches of the federal bans on obstructive and interfering discharges under 40 CFR §403.5.
• Permit suspension or revocation: The hardest penalty is often non-monetary. Loss of the wastewater discharge permit can stop a kitchen from operating until pretreatment is restored.

Citation amounts vary by city and change from time to time. Ask the local AHJ for the current schedule. That means Billings, Missoula, Great Falls, Bozeman, Helena, or your city's public works or wastewater division. Also ask for a copy of the active sewer-use ordinance. Do this before you assume any figure.