Mass. Gen. Laws ch. 21E, § 5
(b) Any person otherwise liable for any costs or damages set forth in subclauses (i), (ii), (iii) and (iv) of paragraph (a) who establishes by a preponderance of the evidence that only a portion of such costs or damages is attributable to a release or threat of release of such oil or hazardous material for which he is included as a party under clauses (1), (2), (3), (4) or (5) of said paragraph (a) shall be required to pay only for such portion.
No person who is liable solely pursuant to clause (1) of paragraph (a) and who did not own or operate the site at the time of the release or threat of release in question and did not cause or contribute to such release or threat of release shall be liable to any person who is liable pursuant to clauses (2), (3), (4), or (5) of said paragraph, except that any such person liable solely pursuant to clause (1) of paragraph (a) shall be liable to the commonwealth as set forth in paragraph (d).
(c) Subject to the limitation provided in paragraph (d), there shall be no liability under paragraph (a) for a person otherwise liable who can establish by a preponderance of the evidence, (A) that the release or threat of release of oil or hazardous material and the damages resulting therefrom were caused by:
(e) All persons liable pursuant to this section who are liable for a release or threat of release for which the commonwealth incurs costs for assessment, containment and removal shall be liable, jointly and severally, to the commonwealth for their liability as set forth in this section.
In an action for recovery by the commonwealth of the costs it incurs for assessment, containment and removal, for the purpose of inducing the party in question and others to voluntarily and without delay participate in carrying out and paying for response actions, and not for the purpose of imposing a penalty, the commonwealth shall have the right to seek and recover more than the actual costs it incurs for assessment, containment and removal, subject to the following provisions.
In cases where the department has issued an order pursuant to sections nine and ten to a person liable pursuant to this chapter and such person has unreasonably or in bad faith failed or refused to comply with such order, the court shall award the commonwealth not less than two times nor more than three times the full amount of its response costs, plus litigation costs and reasonable attorneys' fees, against such liable person. In such an action, the burden of proof shall be on such person to persuade the court by a preponderance of the evidence that it acted reasonably and in good faith in failing or refusing to comply with the department's order. If such person so persuades the court, such person's liability to the commonwealth for response action costs in that action shall be only the department's actual recoverable response costs, plus litigation costs and reasonable attorneys' fees.
In all cases not provided for in the preceding paragraph, the court may award the commonwealth up to three times the full amount of its response costs, plus litigation costs and reasonable attorneys' fees, against a person liable pursuant to this chapter. In such an action, the burden of proof shall be on the commonwealth to persuade the court by a preponderance of the evidence that such person acted unreasonably or in bad faith in not carrying out a response action or actions for which the commonwealth is seeking recovery of more than its actual response costs, aside from litigation costs and reasonable attorneys' fees. If the commonwealth so persuades the court, the court shall use its equitable discretion to determine the appropriate multiple of response costs, not to exceed three times the response costs, which shall be awarded to the commonwealth against such liable person, plus litigation costs and reasonable attorneys' fees. If the commonwealth does not so persuade the court, such person's liability to the commonwealth for response costs in that action shall be only the department's actual recoverable response costs, plus litigation costs and reasonable attorneys' fees.
Without limiting the generality of the foregoing, solely for the purpose of determining whether the commonwealth's recovery may exceed its actual response costs, plus litigation costs and reasonable attorneys' fees, and not for any other purpose, the court shall find that a person against whom the commonwealth seeks such recovery has reasonable grounds and a good faith basis for failing or refusing to perform or pay for a response action for which the commonwealth is seeking such recovery if, within a reasonable time after first being notified by the department that the department wants said person to perform or pay for such response action or actions, said person asserts and demonstrates that performing or paying for such response action or actions was beyond his technical, financial or legal abilities, or that he was not given adequate notice and reasonable opportunity to perform or pay for such response action or actions.
(h) Any person who owns a one- to four-family residence that is a site at which the department has incurred costs for response actions shall not be liable to the department for those costs if he can establish by a preponderance of the evidence that:—
(3) he immediately notified the department of the release of the oil or hazardous material upon the site as soon as he had knowledge of it.
The defense established by this subsection shall not apply (1) if the department can establish by a preponderance of the evidence that said owner knew or had reason to know of the release when he became the owner of the residence or (2) to the cost of any response action necessitated by the leakage of oil from leaking underground storage tanks used to contain oil and underground pipes ancillary thereto or ancillary to above ground storage tanks at the site unless the owner can establish by a preponderance of the evidence that such tanks and pipes were not located on the site at the time of, or installed after the acquisition of the site, and he did not know or have reason to know of the release at the time he acquired ownership or possession of the site. In no event shall said owner be deemed to have had reason to know of the release of oil or hazardous material on the site unless a reasonable inquiry would have disclosed such presence at the time when the site was acquired by said owner, so long as the purchase price paid by said owner bore a reasonable relationship to the value of the site in the absence of oil or hazardous material. For the purposes of this paragraph, a reasonable inquiry shall mean visually inspecting the site for obvious signs of the release of oil or hazardous material. Should such visual inspection indicate that oil or hazardous material had been released at the site, a reasonable inquiry shall also include a further assessment to be performed by or under the supervision of a registered professional engineer, hydrogeologist or other qualified scientist with expertise in such matters. The defense established by this paragraph shall apply to all outstanding claims for costs by the department for response actions conducted or maintained since March twenty-fourth, nineteen hundred and eighty-three.
(j) An agency of the commonwealth and a public utility company that owns a right of way that is a site at which the department has incurred costs for response actions shall not be liable to the commonwealth for those costs if the agency or public utility company, respectively, can establish by a preponderance of the evidence that:
(7) it did not know or have reason to know of the presence of oil or hazardous material on the site when it came into possession of the right of way.
For purposes of this subsection, the phrase ''public utility company'' means the Massachusetts Municipal Wholesale Electric Company established pursuant to chapter seven hundred and seventy-five of the acts of nineteen hundred and seventy-five, or any successor thereto, Massachusetts municipal light departments organized under chapter one hundred and sixty-four or any other special law, and Massachusetts gas and electric companies made subject to the jurisdiction of the department of telecommunications and energy by any provision of law except chapter one hundred and ten A of the General Laws and chapter six hundred and fifty-one of the acts of nineteen hundred and ten, as amended.
(l) Any governmental body or charitable corporation or trust which holds a conservation restriction, agricultural preservation restriction, watershed preservation restriction or affordable housing restriction pursuant to section 32 of chapter 184 shall not be deemed to be an owner or operator if all of the following requirements are met: