What must be removed from a facility before termination of authorization to discharge?

The correct choice highlights the importance of managing materials that could contaminate storm water before a facility is authorized to terminate its discharge. Significant materials—such as chemicals, oils, and other substances—can pose environmental risks if they come into contact with rainwater or storm water runoff. This runoff can carry pollutants into nearby water bodies, potentially violating environmental regulations and harming ecosystems.

By ensuring the removal of all significant materials that may be exposed to storm water, facilities can reduce the risk of pollution and comply with discharge authorization requirements. This is fundamentally important in maintaining water quality and fulfilling regulatory obligations related to storm water management.

The other options, while related to facility closure or compliance, do not specifically address the critical issue of material management concerning storm water exposure. Operational equipment, temporary structures, and landscaping materials may not directly influence the potential for storm water contamination as significantly as hazardous or polluting materials do.