Grease Trap Regulations in Wyoming

Overview of Wyoming FOG Compliance Framework

Wyoming food service operators face a two-layer system. The state sets the legal frame. Cities run the day-to-day pretreatment programs. The Wyoming Department of Environmental Quality (WDEQ), Water Quality Division, oversees water quality permits and sewer construction approvals statewide. Local Boards of Public Utilities and city wastewater divisions enforce the actual fats, oils, and grease (FOG) rules through their own ordinances and discharge permits (WDEQ Water & Wastewater Program).

This split structure is normal across the United States. Federal law under the Clean Water Act delegates pretreatment to Publicly Owned Treatment Works (POTWs). POTWs act as Control Authorities for indirect dischargers like restaurants and institutional kitchens (40 CFR Part 403). The same federal rule bans any discharge of "solid or viscous pollutants in amounts which will cause obstruction" in the sewer. That clause is the legal hook that lets Cheyenne, Casper, Laramie, and other Wyoming cities require grease interceptors at food service sites (40 CFR 403.5(b)(3)).

The reason these rules exist is empirical. In its 2004 Report to Congress, the EPA found that 74 percent of sanitary sewer overflows came from blockages. Of those blockages, 47 percent came from grease, including grease from restaurants, homes, and industrial sources (EPA SSO Report, EPA-833-R-04-001). Wyoming's cold climate, long pipe runs, and spread-out population make this risk worse. Cooled FOG hardens faster in winter, so catching it at the kitchen is the cheapest way to protect the public sewer.

Governing Authorities

The Wyoming Department of Environmental Quality, Water Quality Division issues construction permits for sewer systems and sets statewide water quality standards. It also pursues enforcement under the Wyoming Environmental Quality Act. WDEQ does not publish a single statewide model FOG ordinance. Cities draft their own programs. Most reference the Plumbing & Drainage Institute model and EPA pretreatment guidance (WDEQ Water & Wastewater).

Day-to-day FOG enforcement happens at the city level. The verified municipal contacts and ordinance citations are listed below.

Cheyenne

The Cheyenne Board of Public Utilities (BOPU) Industrial Pretreatment Program handles FOG compliance under Cheyenne City Code 13.20.545 (Cheyenne BOPU FOG Program). BOPU customer service is at (307) 637-6460. The Industrial Pretreatment Program mails to ATTN: IPP, Board of Public Utilities, 2416 Snyder Ave., Cheyenne, WY 82001 (BOPU IPP page). New or expanding food service sites file an Industrial Discharge Survey before connecting (Cheyenne BOPU survey form).

Casper

The City of Casper Wastewater Collection Division enforces pretreatment under Casper Municipal Code Chapter 13.32 (Wastewater Pretreatment), Section 13.32.030 (Casper Municipal Code via Municode). Sewer questions and emergencies route to (307) 235-8481 or (307) 235-8213. The utility office is at 200 N David St., Casper, WY 82601 (Casper Sewer & Wastewater). Casper publishes a "cool, contain, and trash" message for FOG. Cool the grease, store it in a sealed container, and put it in the trash, not down the drain (Casper FOG guidance).

Laramie

The City of Laramie Utility Division Industrial Pretreatment Program runs Laramie Municipal Code Title 13, Chapter 13.78 (Wastewater Pretreatment and Disposal) (Laramie Industrial Pretreatment Program). The Pretreatment Coordinator is at (307) 721-5204. The broader Utility Division is at (307) 721-5280. The utility office is at 4373 N. 3rd St., Laramie, WY 82072 (mailing: P.O. Box C, Laramie, WY 82073). New facilities complete the city's Industrial Waste Survey before discharging (Laramie Industrial Waste Survey).

Rock Springs

The Rock Springs Water Reclamation Facility, Pretreatment and Collections runs FOG compliance under Rock Springs Municipal Code Article 11-6 (Public Sewer System) and Article 7-4 (Plumbing and Sewer Code) (Rock Springs City Ordinance Directory). The Pretreatment and Collections Supervisor is at (307) 352-1466. The Water Reclamation Facility main line is (307) 352-1465. The facility is at 2300 W Sunset Dr (I-80 and Gookins Rd), Rock Springs, WY 82901 (Water Reclamation Facility page). City guidance states that "projects requiring grease traps, sand and grease interceptors, or any special sewage treatment must be approved by the City of Rock Springs Pretreatment and Collections Supervisor at (307) 352-1466. Restaurants and any food service facility must submit plans to the Sweetwater County Health Department" (Rock Springs Building Ordinances). Permit submittals route through the city's Building Inspections & Permits Portal.

Gillette

Gillette runs FOG compliance through its public works and wastewater operations. At the time of writing, a current Pretreatment Coordinator contact and ordinance section could not be confirmed against the city's official .gov site. Operators in Gillette should check the official city website for the active program coordinator, ordinance citation, and submittal forms (City of Gillette).

Installation and Sizing Requirements

Wyoming cities adopt model plumbing codes for grease interceptor design. The 2024 Uniform Plumbing Code, published by IAPMO, is the main reference in the western United States. It underpins most local installation standards (IAPMO). The code splits two unit types. Hydromechanical grease interceptors (HGIs) use baffles and air entrainment in a compact under-sink unit. Gravity grease interceptors (GGIs) rely on large exterior vault volume and longer hold time.

For HGIs, UPC §1014.2.1 caps approved flow rates between 20 and 50 gallons per minute. The Authority Having Jurisdiction can approve other rates (UPC §1014.2.1). The same section limits the total fixture capacity feeding an HGI to no more than 2.5 times the unit's certified gpm flow rate. That cap stops a sudden sink dump from blowing emulsified grease through the unit (UPC §1014.2.1).

Pipe-diameter sizing under UPC Table 1014.2.1(1) gives operators a fast check on whether an existing interceptor matches the kitchen plumbing (UPC Table 1014.2.1(1)):

• 2-inch grease waste pipe: 20 gpm full pipe flow; 20 gpm interceptor for a one-minute drainage period or 10 gpm for a two-minute drainage period.
• 3-inch grease waste pipe: 60 gpm full pipe flow; 75 gpm interceptor for one-minute drainage or 35 gpm for two-minute drainage.
• 4-inch grease waste pipe: 125 gpm full pipe flow; 150 gpm interceptor for one-minute drainage or 75 gpm for two-minute drainage.

For exterior gravity interceptors, UPC §1014.3.6 sets minimum volume by Drainage Fixture Units (DFUs). 8 DFUs need at least 500 gallons. 21 DFUs need 750 gallons. 35 DFUs need 1,000 gallons. 90 DFUs need 1,250 gallons (UPC §1014.3.6). Gravity units must be installed outside the building. The Authority Having Jurisdiction can approve an indoor location in a well-ventilated, normally unoccupied space (UPC §1014.3.4).

The parallel International Plumbing Code is used in many eastern states and is referenced by some Wyoming building departments. It requires a grease interceptor or automatic grease removal device for fixtures and equipment with grease-laden waste in restaurants, hotel kitchens, hospitals, school kitchens, bars, factory cafeterias, and clubs. Covered fixtures include pot sinks, prerinse sinks, soup kettles, wok stations, floor drains, and sinks into which kettles are drained (IPC §1003.3.1). The IPC defines a Gravity Grease Interceptor as a plumbing appurtenance of not less than 500 gallons capacity (IPC Chapter 2 Definitions).

Final sizing, slope, baffle layout, and sampling-port detail must be approved by the local wastewater utility before install. Cheyenne, Casper, and Laramie each require plan review through their pretreatment programs above (Cheyenne BOPU; Casper Code Ch. 13.32; Laramie IPP).

Cleaning and Maintenance Frequency

The shared rule across municipal FOG programs is the 25% Rule. A grease interceptor must be serviced before the combined volume of floating FOG and settled solids passes 25 percent of the unit's liquid volume (EPA National Pretreatment Program). Once that line is crossed, the active clear-water zone is too thin to slow incoming wastewater enough for separation. Emulsified grease then passes into the public sewer.

Cheyenne sets a specific minimum interval. The BOPU tells facilities to "clean the grease interceptor every 90 days or at a frequency specified by the Board of Public Utilities" under Cheyenne City Code 13.20.545 (Cheyenne BOPU FOG Program). The same guidance tells operators to verify the interceptor and its parts are in place and fully working. Operators must email or mail the cleaning manifest from the hauler to the IPP within 14 days of service (Cheyenne BOPU 14-day manifest rule).

Laramie takes a discretionary approach under Chapter 13.78. The Superintendent approves the cleaning frequency and may adjust it based on observed maintenance practices. Operators must give a copy of the most recent cleaning record to the Superintendent within five days of service (Laramie Municipal Code Chapter 13.78).

Casper does not publish a fixed numeric pumping cycle for food service sites in the public-facing portions of Chapter 13.32. The city emphasizes source reduction (cool, contain, trash) and case-by-case enforcement through the Wastewater Collection Division (Casper Municipal Code Ch. 13.32; Casper Sewer & Wastewater). Operators in Casper, Gillette, and Rock Springs should confirm their site's specific frequency directly with the wastewater utility. The 25% Rule is the operational floor.

No matter the city, partial skimming does not count as a service event under standard pretreatment practice. A compliant pump-out removes all FOG, solids, and wastewater. The hauler then takes the load to a permitted receiving facility for disposal.

Record-Keeping and Manifest Requirements

Federal pretreatment rules set the recordkeeping floor for industrial users, including covered food service sites. Records of monitoring activities and results must be kept for at least three years. The period extends automatically during any unresolved litigation involving the discharge or the POTW pretreatment program (40 CFR 403.12(o)(2)).

Laramie applies a longer local standard. Chapter 13.78 tells each user to keep on record for at least five years all cleaning and other maintenance done to the grease trap or grease filtering device. Records must be available to the Superintendent on request. A copy of the most recent cleaning record must be submitted within five days of service (Laramie Municipal Code Chapter 13.78).

Cheyenne's manifest workflow is procedural rather than calendar-based. Each cleaning manifest from the licensed hauler must reach the Industrial Pretreatment Program within 14 days of the service, by email or mail (Cheyenne BOPU FOG Program). A complete manifest documents the service date, gallons removed, hauler ID, and the disposal facility that took the waste.

Operators should also keep, alongside hauler manifests, the original install permit and as-built drawings. Add internal inspection logs that document FOG and sludge depth. Keep any best management practice training records for kitchen staff. These supporting records are what auditors look for when a manifest gap or a sewer backup triggers a site visit.

Fines and Penalties

State-level enforcement authority for environmental violations sits in Wyoming Statutes §35-11-901. That includes unpermitted FOG discharges that affect public sewers under the Wyoming Environmental Quality Act (Wyoming State Legislature). The penalty tiers rise sharply based on intent and history (W.S. §35-11-901):

• Standard civil violation: up to $10,000 per day of violation (W.S. §35-11-901).
• Willful or knowing violation: up to $25,000 per day, with possible imprisonment (W.S. §35-11-901).
• Subsequent conviction: up to $50,000 per day, with possible imprisonment (W.S. §35-11-901).

These caps are statutory ceilings, not the typical first-incident outcome. In practice, WDEQ and local utilities open with a Notice of Violation and a corrective compliance schedule. They escalate to formal orders and administrative penalties if the facility fails to act. The most serious or repeat cases get referred for civil penalty assessment under §35-11-901 (W.S. §35-11-901; WDEQ Water Quality Division).

City pretreatment programs run their own enforcement on top of the state statute. Cheyenne's BOPU can require added sampling, raise cleaning frequency, or refer cases to the city attorney when an operator misses manifests or breaks local discharge limits (Cheyenne BOPU IPP). Laramie's Superintendent may raise cleaning frequency based on observed performance under Chapter 13.78 (Laramie Municipal Code Chapter 13.78). Casper, Gillette, and Rock Springs each enforce through their own wastewater divisions and city ordinance procedures (Casper Municipal Code; City of Gillette; City of Rock Springs).

The cost math for an operator is simple. A scheduled pump-out and a manifest filed on time costs a small fraction of one day at the §35-11-901 standard penalty tier (W.S. §35-11-901). It also avoids the much larger downstream cost of a sewer backup, a health closure, or a referral to a willful or subsequent-conviction tier.