In addition to any reporting of an actual or confirmed release, the owner must also take steps to identify, mitigate and monitor fire and explosion hazards, such as the presence of free product or vapors in the tank excavation.
The owner must also take action to prevent further release of the regulated substance to the environment.
This includes removing and safely storing as much of the regulated substance from the tank excavation and tank system as necessary, and taking any steps needed to prevent the migration of the regulated substance. These procedures are specified in API RP1604 - Closure of Underground Petroleum Storage Tanks.
Commerce publishes a guide for the assessment and reporting of suspected and obvious releases from UST systems. You can access and download this guide to your desktop from the Commerce Storage Tank Regulation home page.
As the Class A operator you are responsible to verify that all of the above activities and tasks are completed, and ensure that copies of the proper documentation is maintained for future reference.