What is an underground storage tank (UST) commonly used for?

An underground storage tank (UST) is commonly used for storing heating oil in residential areas as well as gasoline and other petroleum products. These tanks are typically installed underground to protect the contents from environmental effects and to minimize the risk of fire or explosion. USTs are also designed to prevent leaks, which is essential because petroleum products can be hazardous to the environment and human health if they leak into the ground or groundwater.

The use of USTs for heating oil specifically allows homeowners to store fuel for heating systems safely. This is particularly relevant in regions where home heating is dependent on oil as a primary source of energy. The other choices do not accurately reflect the primary functions of USTs. For instance, while hazardous waste can be stored in similar tanks, USTs are not solely dedicated to this purpose. Similarly, freshwater supplies are typically not stored in USTs due to the potential for contamination, and collecting rainwater is generally managed using different systems, such as above-ground cisterns or rain barrels. Therefore, the correct answer reflects the primary use of USTs in residential settings for heating oil storage.