How long after temporary closure should a tank be permanently closed by a certified UST supervisor?

The requirement for how long a UST can remain temporarily closed before it must be permanently closed is based on established regulations. In Washington State, once a tank is temporarily closed, it must be permanently closed within a maximum period of 12 months to ensure safety and environmental protection. This timeframe is critical because prolonged storage in a temporary status could lead to potential leaks or contamination, which may pose significant risks to the surrounding environment and public health. Therefore, having a 12-month limit helps ensure that any risks associated with the storage tank are adequately managed.

The other options do not align with this regulatory timeline, leading to insufficient monitoring or control of potential hazards that may arise during a prolonged temporary closure. Thus, the correct response is indeed based on compliance with regulatory standards aimed at promoting safety and environmental integrity.