Define “closure” with respect to USTs.

Closure, in the context of underground storage tanks (USTs), refers to the process of properly shutting down and decommissioning a UST when it is no longer in use. This involves specific guidelines and procedures to ensure that the tank is safely taken out of operation, including emptying and cleaning the tank, removing it if necessary, and properly disposing of any remaining materials. The closure process is vital to prevent environmental contamination, especially from hazardous materials that may have been stored in the UST.

This definition highlights the importance of compliance with environmental regulations and emphasizes safety and proper procedure in ensuring that the closure is handled effectively. Proper closure is essential for protecting groundwater and other environmental resources from potential leaks or spills, which is why it stands out as the correct choice.