Section 4. The department, whenever it has reason to believe that oil or hazardous material has been released or that there is a threat of release of oil or hazardous material, is authorized to take or arrange for such response actions as it reasonably deems necessary. Releases and threats of release for which the department undertakes such response actions, and the extent of such response actions, shall be determined by reference to the Massachusetts contingency plan. Prior to undertaking any response action, the department shall notify the owner or operator of the site or vessel or a fiduciary, city or town or secured lender that has title to or possession of a site or vessel of its intent to take such action. Such notice shall not be required when the department does not know the identity or location of the owner or operator or of a fiduciary, city or town or secured lender that has title to or possession of a site or vessel, or when because of an emergency or other circumstances, the giving of such notice would be impractical. In the event the department and the department of public health jointly determine the need for, scope and cost of a study of the public health effects of a release or threat of release of oil or hazardous material, the department shall provide for the conduct of such a study under the direction of the department of public health.

Nothing in this section shall preclude assessment, containment and removal by any person threatened or damaged by such release or threat of release, provided such assessment, containment and removal is conducted in accordance with the Massachusetts contingency plan and consistently with assessment, containment and removal actions conducted by the department. Chemicals shall not be used in the assessment, containment and removal of released oil or hazardous materials unless and until their use has been authorized by the department.

Any person who undertakes a necessary and appropriate response action regarding the release or threat of release of oil or hazardous material shall be entitled to reimbursement from any other person liable for such release or threat of release for the reasonable costs of such response action. If two or more persons are liable pursuant to section five for such release or threat of release, each shall be liable to the others for their equitable share of the costs of such response action. All claims and actions for contribution, reimbursement or equitable share by persons other than the commonwealth pursuant to this paragraph, except those pending in court on the effective date of section four A shall be subject to, and brought in accordance with, the procedures set forth in section four A.

Any person who without charge renders assistance at the request of a duly authorized representative of the department in removing oil or hazardous material released shall not be liable, notwithstanding any other provision of law, for civil damages as a result of any act or omission by him in removing such oil or hazardous material, except for acts or omissions of gross negligence or willful misconduct.

Any person, except a person who is liable pursuant to clause (1) of paragraph (a) of section five, who provides care, assistance or advice in response to a release or threat of release of oil into or on to the tidal waters of the United States including without limitation the territorial sea, or to any tidal shorelines adjoining any waters of the United States, or to the zone established by Presidential Proclamation numbered 5030 dated March tenth, nineteen hundred and eighty-three, including without limitation, the ocean waters of the areas referred to as ''eastern special areas'' in Article 3 (1) of the Agreement between the United States of America and the Union of Soviet Socialist Republics on the Maritime Boundary, signed June first, nineteen hundred and ninety, and said care, assistance or advice is consistent with applicable state law, or the National Contingency Plan or as otherwise directed by the federal on-scene coordinator predesignated by the United States Environmental Protection Agency or the United States Coast Guard to coordinate and direct a federal response for oil removal under subpart D of the National Contingency Plan, or by the state official with responsibility for oil spill response shall not be liable, notwithstanding any other provision of law, including section five, for removal costs or damages which result from actions taken or omitted to be taken in the course of providing such care, assistance, or advice, except with respect to personal injury or wrongful death, or if such person is grossly negligent or engages in willful misconduct. For the purposes of this paragraph, the term damages shall mean any damages, costs, expenses or economic loss of any kind for which liability may exist under the laws of this state resulting from, arising out of or related to the discharge or threatened discharge of oil. As used in the preceding sentence, the term discharge shall mean any emission, other than natural seepage, intentional or unintentional, and including but not limited to spilling, leaking, pumping, pouring, emitting, emptying or dumping of oil, oil refuse, oil mixed with wastes, other than dredge spoil, or petroleum, but not including hazardous substances which are specifically listed under 42 USC 9601 (14) (A) through (F) and which are subject to the provisions of that Act. Nothing in this section shall affect the liability of a person as described in clause (1) of paragraph (a) of section five, for oil spill response under any other provision of the General Laws.