Which of the following is NOT a common material for UST construction?

Concrete is generally not a common material for underground storage tank (UST) construction due to several factors. While concrete may be used in some configurations, it is not suitable as a primary construction material for USTs because of issues related to groundwater permeability and chemical resistance. Most USTs are constructed from materials that can effectively contain hazardous substances and resist corrosion and degradation.

Steel, fiberglass-reinforced plastic, and double-walled systems are common choices because they offer enhanced durability, longevity, and safety. Steel tanks are robust and can be treated for corrosion protection. Fiberglass-reinforced plastic is known for its resistance to a variety of chemicals, making it suitable for storing fuel and other hazardous liquids. Double-walled systems provide an additional layer of containment, minimizing the risk of leaks and environmental contamination, which is critical for UST compliance and safety. Thus, the context demonstrates that concrete is not typically used for USTs, making it the correct answer to identify as NOT a common material in UST construction.