Which type of tank is designed specifically for preventing environmental spills and leaks?

Double-walled tanks are designed specifically with an inner and an outer wall, providing an additional layer of protection against spills and leaks. The space between these two walls acts as a secondary containment area. This design is crucial for preventing environmental contamination as it captures any potential leaks from the inner tank before they can escape into the surrounding environment.

In contrast, single-walled tanks only have one layer, which offers no secondary containment, making them more susceptible to environmental risks if they develop leaks. Open air tanks expose contents directly to the atmosphere, which does not provide any practical solution for preventing spills onto the ground. Portable tanks, while useful for transport, also do not have the necessary design features to prevent environmental spills in a stationary context. Therefore, double-walled tanks are the preferred choice for minimizing the risk of environmental contamination.