(a) An engineer or contractor performing a program of remedial action or cleanup of hazardous waste or solid waste under a contract with a state agency or political subdivision of the state is liable under this subchapter for any negligent act or omission or for wilful misconduct that results in an actual or threatened release of hazardous waste or solid waste after the abandonment or conclusion of the program only to the extent that the endangerment to public health and safety or the environment is aggravated as a result of the act, omission, or misconduct.
(b) In this section, "engineer or contractor" means a person, including the employee or subcontractor of the person, who performs a contract for evaluation, planning, designing, engineering, construction, equipment, or auxiliary services in connection with:
(1) identifying a hazardous or solid waste site;
(2) developing a plan to clean up the site; or
(3) supervising or implementing the plan to clean up the site.