To be subject to EPA rules, what must be the capacity of a UST?

The correct answer is based on the regulatory framework established by the Environmental Protection Agency (EPA) concerning underground storage tanks (USTs). The EPA requires that any underground storage tank with a capacity of 110 gallons or more must comply with specific regulations aimed at preventing leaks and protecting the environment. This regulatory threshold is set to ensure that larger tanks, which have a greater potential impact on the environment if they leak, are subject to stricter controls and monitoring.

This means that just having a capacity of 110 gallons triggers the requirement for adherence to EPA guidelines, including proper installation, maintenance, and monitoring practices to mitigate risks to groundwater and soil contamination. Tanks under this threshold may not be required to follow the same stringent regulations, which is why the capacity figure is crucial.

In summary, a UST must have a minimum capacity of 110 gallons to be subject to EPA rules, making this option the correct choice.