Comm 10 Clarification

Several questions have been posed relating to the overfill requirements on USTs. The Comm 10 Spill and overfill prevention requirement applies as below:
Heating oil tanks (Comm 10.310 (5)) refers to Comm 10.505 for USTs 4,000 gallons or greater. Comm 10.310 (3) requires overfill prevention for heating fuel tanks less than 4K, but via other methods.

Comm 10. 350 Hazardous substance tanks overfill prevention is not addressed due to the specific compatibility issues and hazardous substance properties and characteristics.
Comm 10.505 applies to USTs that take delivery via a tight connect with the delivery hose. This applies regardless of the tank being "12,000 gallons, but being filled no more than 50% of capacity."

For USTs that routinely take delivery by hand-held nozzle and the fill pipe is not equipped with a tight connect fitting auto-shut-off is not required. Maintaining a tight connection with a hand-held nozzle poses a challenge, even with the gasket collar, and in many situations where a drop is via a "hand held nozzle, if the tank had a flapper type auto shut-off, when the shut-off activates it would produce a safety concern from blow back at the person fuelling and the surrounding area.

PEI RP 100-05-7.3.2 includes the following: "Shut-off devices that are designed for use with underground tanks should only be used with gravity deliveries and where there are liquid-tight connections between the delivery hose and the fill pipe."

Sheldon Schall, Chief
Storage Tank Regulation Section
Wisconsin Department of Commerce

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