(a) This section applies at a site where the owner and the operator are different persons or at a site where there is more than one underground storage tank, petroleum storage tank, or a combination of both.
(b) Each owner and operator of an underground storage tank or petroleum storage tank at a site to which this section applies and from which a release or threatened release occurs is responsible for taking all corrective action at the site which may be required under this subchapter; provided that liability for the expenses of corrective action among owners and operators may be apportioned as provided by this section.

(c) All owners and operators of underground storage tanks and petroleum storage tanks at a site to which this section applies shall attempt to negotiate a settlement among themselves as to the apportionment of expenses.
(d) If the owners and operators reach a settlement as to the apportionment of expenses on or before the 30th day from the date on which the commission issues an order requiring corrective action, they shall submit the settlement to the commission for review. If the commission approves the settlement, the parties shall be liable for the expenses of taking corrective action in accordance with the approved settlement. Any action for breach of contract on the settlement agreement shall be to the district court of Travis County.
(e) If the parties cannot reach a settlement by the 30th day after the commission issues its order, the commission shall file suit in the district court of Travis County. In its petition, the commission:
(1) shall request the court to apportion the expenses of corrective action among the owners and operators; and
(2) may request the court to award recovery of costs as provided by § 26.355 of this code. In the alternative, the commission may file an action for recovery of costs at a later time.
(f) Where the owner or operator can prove by a preponderance of the evidence that liability for the expenses of taking corrective action in response to a release or threatened release is divisible, that person shall be liable for the expenses only to the extent that the impact to the groundwater, surface water, or subsurface soils is attributable to the release or threatened release from his underground storage tank or petroleum storage tank.
(g) The court may allocate corrective action costs among liable parties, using such equitable factors as the court determines are appropriate if the evidence is insufficient to establish each party’s divisible portion of the liability for corrective action under Subsection (f) of this section and joint and several liability would impose undue hardship on the owners and operators.
(h) If the court apportions liability for the expenses of corrective action as provided by Subsection (f) or (g) of this section, cost recovery against the owners and operators shall be based on the apportionment.
(i) The commission may use the petroleum storage tank remediation account to take corrective action at any time before, during, or after the conclusion of apportionment proceedings commenced under this section.
(j) Any owner or operator of a petroleum storage tank at the site may voluntarily undertake such corrective action at the site as the commission may agree to or require. An owner or operator who undertakes corrective action pursuant to this subsection may have contribution against all other owners and operators with tanks at the site.
(k) Nothing in this section:
(1) prohibits the commission from using the waste management account to take corrective action as provided by this subchapter and having cost recovery for the waste management account; or
(2) affects the assessment of administrative penalties by the commission for violations of this subchapter or rules or orders adopted thereunder.
(l) At the request of the commission, the attorney general shall file suit on behalf of the commission to seek the relief provided by this section.
(m) The commission shall consider the person who is in day-to-day control of a petroleum storage tank system at a site that is in violation of this subchapter to be the:
(1) person primarily responsible for taking corrective action, for corrective action costs, for receiving a notice of violation, or for paying a penalty assessed; and
(2) primary subject of an enforcement action or order under this subchapter.