Tanks of ________ gallons or less capacity are exempt from federal UST regulations.

• A. 100
• B. 120
• C. 150
• D. 110

Answer: (D)

Underground storage tanks (USTs) have a size-based exemption in federal regulations. Tanks with a capacity of 110 gallons or less are not subject to most federal UST requirements, such as leak detection, spill and overfill prevention, corrosion protection, and operator training. The reasoning is to reduce regulatory burden for very small storage while still focusing oversight on larger systems that pose greater environmental risk. Therefore, the standard threshold used in the regulations is 110 gallons, which is why that value is the correct fill-in. Tanks larger than that threshold would fall under the federal requirements.