(a) Owners and operators of underground storage tanks shall, in response to all confirmed releases, comply with all applicable statutory and regulatory reporting and response requirements.
     (b) Notwithstanding any other corrective action taken, an owner or operator may, at a minimum, and prior to submission of any plans to the Agency, remove the tank system or abandon the underground storage tank in place, in accordance with the regulations promulgated by the Office of the State Fire Marshal. The owner or operator may also remove visibly contaminated fill material and any groundwater in the excavation which exhibits a sheen. For purposes of payment for early action costs, however, fill material shall not be removed in an amount in excess of 4 feet from the outside dimensions of the tank.