40 CFR 63 Subpart 6C: EPA Gasoline Dispensing

Regulatory citation: 40 CFR Part 63, Subpart CCCCCC, National Emission Standards for Hazardous Air Pollutants for Source Category: Gasoline Dispensing Facilities

What Is the 6C Rule?

Subpart CCCCCC, often called the 6C rule, is an area source air toxics standard for gasoline dispensing facilities (GDFs). A GDF is any stationary facility that dispenses gasoline into the fuel tank of a motor vehicle. The rule covers retail gas stations, fleet fueling sites, rental car lots, municipal yards and similar facilities, including their storage tanks and cargo tanks during delivery. Loading aviation gasoline at airports is excluded, and the rule does not by itself require a Title V permit.

Why the 6C Rule Matters

Gasoline vapor contains benzene and other hazardous air pollutants. Most vapor escapes when a tanker fills an underground or aboveground tank, pushing vapor out of the tank vent. Submerged fill and vapor balance systems keep most of that vapor in the system.

Core Requirements

1. Calculate Monthly Throughput (63.11111 and 63.11132)

Requirements depend on monthly throughput, calculated on a rolling basis: total gasoline loaded into or dispensed from all tanks for the current day plus the previous 364 days, divided by 12. Once a facility moves into a higher tier, it stays in that tier even if throughput later drops. A facility that rises into a higher tier has 3 years to comply.

2. Follow Work Practices at Every Facility (63.11116)

All GDFs must minimize gasoline spills, clean up spills promptly, cover open gasoline containers and fill pipes with gasketed seals when not in use, and minimize gasoline sent to open waste collection systems. Facilities under 10,000 gallons a month need no notifications or reports, but must make throughput records available within 24 hours of a request.

3. Use Submerged Fill at 10,000 Gallons a Month or More (63.11117)

Facilities at or above 10,000 gallons a month must also fill tanks through a submerged fill pipe. Fill pipes installed on or before November 9, 2006 must end no more than 12 inches from the tank bottom. Those installed later must end no more than 6 inches from the bottom. Tanks under 250 gallons are exempt. An Initial Notification is required.

4. Install Stage I Vapor Balance at 100,000 Gallons a Month or More (63.11118 and Table 1)

Facilities at or above 100,000 gallons a month must also use a vapor balance system during tank deliveries. Vapor connections must seal on disconnect, vapor lines must be vapor-tight, and cargo tank pressure must stay at or below 18 inches of water pressure and 5.9 inches of water vacuum during transfer. Adaptors must resist over-tightening and loosening, and gauge wells need submerged drop tubes. New facilities, and tanks built after November 9, 2006, need dual-point systems. Some small tanks and floating-roof tanks are exempt from vapor balance but must still use submerged fill.

5. Set and Test Pressure/Vacuum Vent Valves (Table 1 and 63.11120)

Pressure/vacuum (PV) vent valves must open at a positive pressure of 2.5 to 6.0 inches of water and a negative pressure of 6.0 to 10.0 inches of water, within set leak rate limits. Facilities in the vapor balance tier must test PV valves and run a static pressure test of the vapor system at installation and every 3 years after. Cargo tanks that deliver to these facilities need annual vapor-tightness certification.

6. Submit Notifications and Reports (63.11124 and 63.11126)

Facilities at or above 10,000 gallons a month submit an Initial Notification within 120 days of becoming subject. Facilities in the vapor balance tier also submit a Notification of Compliance Status and a notification at least 60 days before a performance test. Test results are reported within 180 days, and an annual malfunction report is due by March 15 if a malfunction occurred.

7. Keep Records for 5 Years (63.11111(e) and 63.11125)

Keep throughput records, test results, cargo tank vapor-tightness records and malfunction records for 5 years.

Common Compliance Approaches

Track Throughput Every Month

Use fuel delivery or dispensing records to update the rolling average each month, so a move into a higher tier is caught early.

Build a Delivery Checklist

Check that the vapor hose is connected before product flows, caps and adaptors are tight, and spill buckets are clean after each drop.

Calendar the 3-Year Tests

Schedule PV valve and static pressure tests well before the due date and keep the reports with your compliance file.

Example: 6C Compliance in Practice

A convenience store dispenses about 120,000 gallons of gasoline a month, so it falls in the vapor balance tier. Its underground tanks have submerged fill pipes and a dual-point Stage I vapor balance system. Before each delivery, the driver connects the vapor return hose first. Every 3 years, a contractor tests the PV vent valves and runs a static pressure test, and the store keeps the results, throughput records and its compliance notification for 5 years.

Related regulations: EPA underground storage tanks, EPA SPCC rule, EPA Title V operating permits.

Note: EPA's 2024 gasoline distribution rule and its 2026 reconsideration proposal covered bulk terminals, bulk plants and pipeline facilities, not gasoline dispensing facilities. Subpart CCCCCC was last amended in 2020 and 2021. Many states set stricter rules, including lower vapor balance thresholds and Stage II vapor recovery, so check your state air agency's requirements.

Frequently Asked Questions

Does the 6C rule apply to my fleet fueling site?

Yes, if it is a stationary facility that dispenses gasoline into motor vehicle fuel tanks and is at an area source. Requirements depend on monthly throughput.

How is monthly throughput calculated?

Add the gasoline loaded into or dispensed from all tanks for the current day and the previous 364 days, then divide by 12. It is a rolling average, not a single calendar month.

Do small gas stations have to do anything?

Yes. Facilities under 10,000 gallons a month must follow the work practices, such as minimizing spills and keeping containers covered, and must provide throughput records within 24 hours of a request.