Such city or county ordinance shall take effect 60 days from the date of adoption by the city or county, unless the regional board holds a public hearing on the matter and determines that the city or county ordinance is not sufficiently restrictive to protect the quality of the waters affected. If the board makes such a determination, it shall so report to the affected city or county and also recommend the ordinance, or modification of the city or county ordinance, which it determines is necessary.