1. Introduction to Overfill Prevention for USTs
Presented by: Ted Unkles
UST Program Coordinator
Vermont Dep’t of Environmental Conservation
Montpelier, Vermont
(802)

2. Overfill prevention: why is it important?
Tank overfills can result in large spills.
One particularly awful overfill in Biloxi, Mississippi, released more than 500 gallons of gasoline (August 9, 1998).

3. Biloxi Overfill tragedy
Gas flowed into the street and caught fire.
5 people sitting in traffic died in the fire; a 6th survived but was severely burned.

4. Overfill prevention: Regulatory Requirements
Federal UST Regs: 40 CFR§280.20(c) for new UST systems, and (d), for existing UST systems.
Most states (probably all) have requirements in their UST regs that mirror these federal requirements.

5. Overfill prevention – regulatory requirements
All regulated UST systems must have a device that will do one of the following:
Stop delivery when the tank is no more than 95% full; or
Slow down the delivery when the tank is no more than 90% full; or
Alert the delivery driver with a high level alarm one minute before overfilling.

6. Overfill prevention – regulatory requirements
Other options -- Federal regs also allow devices that will:
restrict flow 30 minutes prior to overfilling, or
automatically shut off flow so that product never touches any tank-top fittings.
These options are not commonly used, and many states do not allow them.

7. Automatic fill pipe shutoff (a.k.a. “flapper valve.”)

8. Automatic Fill Pipe Shutoff
They can be set at 95% of the tank’s capacity.
If the hose is not attached to the fill pipe securely, it can come loose.
If the drop tube is not mounted properly inside the fill pipe, the whole unit can be slammed into the bottom of the tank.

9. Ball Float Valve (a.k.a vent restriction device)

10. Ball Float Valve

11. Ball Float Valve

12. Ball Float Valves All fittings on top of the tank must be vapor-tight.
They cause pressurization of the vapor space, which can cause problems with vapor recovery systems.
They don’t work with coaxial vapor recovery systems.
If a tank has a remote fill the gauging port must be capped tightly.

13. Ball Float Valves
Ball Float valves are not allowed on new UST systems.
But many tanks are equipped with ball floats, and they can still be used as long as they continue to function properly.

14. Audible Alarm
The alarm must be visible and/or audible to the driver making the delivery.
Too often, the alarm is inside the building, as part of the console.
The alarm itself does nothing to stop the flow into the tank. The driver has to stop the flow manually.

15. Quick Summary
All regulated USTs must be equipped with a device that will do one of the following:
Stop delivery at 95% full (auto fill pipe shutoff); or
Slow delivery at 90% full (ball float) – but remember, these are not allowed for new UST systems;
Alert the delivery driver 1 minute before overfill occurs (audible alarm).

16. Questions? Call me at (802) 522-0488, or
me at: