Whenever this code of ordinances grants any discretionary power to the Board of Supervisors or any commission, board or officer or employee of the county and does not specify standards to govern the exercise of the power, the power shall be exercised in light of the following standard: the discretionary power to grant, deny or revoke any matter shall be considered in light of the facts and circumstances then existing and as may be reasonably foreseeable, and due consideration shall be given to the impact upon the public health, safety and welfare, and the decision shall be that of a reasonably prudent person under similar circumstances in the exercise of the police power.