(a)
(1) Any party found liable for any costs or expenditures recoverable under §§ 8-7-512, 8-7-514, 8-7-515, and 8-7-517 which establishes by a preponderance of the evidence that only a portion of such costs or expenditures are attributable to his or her actions shall be required to pay only for that portion.
(2) If the trier of fact finds the evidence insufficient to establish each party's portion of costs or expenditures, the court shall apportion the costs or expenditures, to the extent practicable, according to equitable principles, among the responsible parties.
(3) The Hazardous Substance Remedial Action Trust Fund shall pay any portion of the total expenditure in excess of the aggregate amount of costs or expenditures apportioned pursuant to this section.
(b)
(1) In any action under this section, no responsible party shall be liable for more than that party's apportioned share of the amount expended from the fund for the hazardous substance site.
(2) The apportioned share shall be based on a responsible party's total volume of the hazardous substance at the hazardous substance site at the time of action taken under this subchapter.
(3) Any expenditures required by the provisions of this subchapter made by a responsible party, before or after suit, shall be credited toward any apportioned share.