Before permanently closing a UST that remains in the ground, which action must be taken?

• A. Notify the DEQ within 5 days
• B. Remove the tank from the ground
• C. Recycle the tank as scrap
• D. Fill with inert solid material

Answer: (D)

When permanently closing a UST that remains in the ground, the essential step is to fill the tank with inert solid material. This inert fill immobilizes the tank, prevents the creation of voids, and reduces the risk of ground subsidence or future contamination pathways if any residual contents were present. It effectively seals the tank in place so it cannot become a conduit for leaks.

In practice, you would first ensure the tank is emptied and any vapors are addressed, and then place inert material (such as concrete or other solid, non-reactive fill) into the tank until it is completely filled.

Other options aren’t the required closure action in this scenario: notifying the regulatory agency is a regulatory step that may occur as part of the process, but does not physically close the tank; removing the tank from the ground or recycling it is relevant only if you’re closing by removal, not when closing in place.