The head of a public agency may exempt a particular project, contract, subcontract, grant, tax abatement, or tax credit from the requirements of Section 39-8-4 if the public agency finds, after public notice and hearing, that special circumstances require an exemption to avert an imminent threat to public health or safety. A finding of special circumstances under this section shall not be based on the possibility or presence of a labor dispute concerning the use of contractors or subcontractors who are nonsignatories to, or otherwise do not adhere to, agreements with one or more collective bargaining organizations, or concerning employees on the project who are not members of or affiliated with a collective bargaining organization.