What additional requirements are mandated for a UST system closed for 3 months or more?

Selecting the option that stipulates leaving vent lines open while capping and securing other lines, as well as performing tightness tests, aligns with best practices for managing a UST system that has been closed for 3 months or more. This procedure ensures that the fuel system remains safe from environmental contamination and potential hazards associated with vapor buildup.

Specifically, keeping the vent lines open allows for pressure equalization, which is vital to prevent the tank from collapsing or experiencing structural damage due to changes in temperature or atmospheric pressure. Sealing other lines helps to prevent any potential leaks from going undetected, while the tightness tests are a critical measure for identifying any leaks that may have developed prior to the closure. This approach mitigates environmental risks and complies with regulatory standards ensuring the UST is maintained in a responsible manner during a period of inactivity.

Other options, while related to UST management in some capacity, do not adequately address the particular requirements for systems that have been out of use for extended periods. For instance, seals on openings may not be sufficient in terms of pressure management, and simply conducting a full inspection does not include the necessary actions for venting and securing lines or monitoring for leaks. Removing the tank entirely is not typically mandated simply due to a