The State Health Commissioner may close any crustacea, finfish or shellfish growing area without a hearing or an investigation, if he has substantial evidence or information that such area is polluted or likely to be polluted. In such event, the State Health Commissioner shall, within thirty days after such closure or declaration, either reopen the area or make the examination, inspection, and analysis provided for in §§ 28.2-803 through 28.2-808. If such grounds or area is not reopened or declared not polluted within thirty days after closure or declaration of pollution, any leaseholder in the growing area may demand and have a public hearing as to the conditions of the ground or area.