For which situation is a double-walled tank typically required?

A double-walled tank is typically required for underground installations due to safety and environmental protection concerns. The outer wall of the double-walled tank acts as a secondary containment barrier designed to prevent the escape of fuel or hazardous materials into the surrounding soil or groundwater in case of a leak from the inner tank. This is particularly important for underground tanks, where leaks can go undetected for extended periods and can cause significant environmental contamination.

Furthermore, regulations are often stricter for underground installations in recognition of the potential risks associated with fuel storage below ground. By using double-walled tanks in these situations, the risk of leaks and subsequent environmental damage is significantly mitigated, aligning with the standards outlined in the Maine Fuel Code and similar regulations.

While aboveground and portable installations may also have their own safety requirements, these typically do not necessitate the use of double-walled tanks to the same extent as underground tanks, where the likelihood and potential impacts of leaks are higher.