Which of the following is a requirement for mounting horizontal outside oil tanks?

The requirement for mounting horizontal outside oil tanks includes the use of floor flanges at the base of the steel leg. This is crucial because floor flanges provide stability and support for the tanks, preventing shifting or tipping caused by external factors such as wind or seismic activity. Proper support helps maintain the integrity of the tank and reduces the risks of leaks or spills, which can have environmental consequences.

Floor flanges create a strong and secure connection between the tank legs and the mounting surface, which is necessary for the safe and effective operation of the tank. This contributes to compliance with safety regulations outlined in the Maine Fuel Code and helps ensure that the oil tank operates safely while minimizing risks.

The other options, while related to the overall setup of oil tanks, do not represent a standard requirement like the use of floor flanges. For instance, while concrete pads can provide a solid base, they are not explicitly required in every installation, and allowing open air beneath the tank may not always be feasible or safe, depending on site conditions. Wooden supports, while they may be used for temporary measures, are generally not considered a best practice for the long-term stability of metal tanks.