The commission shall not approve any site and related facility unless it determines that there is a substantial likelihood that it will meet the applicable air quality regulations; provided, however, that if the commission determines that the facility is urgently needed, the applicant has made a good faith effort to find acceptable alternative sites and related facilities, and no otherwise approvable site has a substantial likelihood, it may approve the single site and related facility that is otherwise acceptable and that is most likely to meet all applicable air quality regulations. In such event, the commission shall request the ARB and local districts to appear at the hearings on the final report and advise the commission on which site is most likely to meet the requirements.