Upon presentation of any such petition said board of supervisors shall proceed to a consideration thereof. The said board shall have authority to make any necessary surveys, procure any appropriate plans and specifications, obtain estimates of probable cost of construction and take any other appropriate step for procuring necessary or desirable information with reference to the project embodied in such petition. Said board shall have full authority, by a majority vote of those voting thereon, to grant or deny the object of such petition and to determine the character and type of construction of any such bridge ordered thereon. The several boards of supervisors of the counties of the state shall each likewise have authority, upon their own initiative, respectively, in a proper case, in the discretion of any such board, to order the construction of a bridge over any navigable stream or water within the county, as hereinbefore provided in cases when a petition is presented to a board of supervisors by a city, village or township for the construction of a bridge. Whenever in any case a bridge shall be ordered hereunder, said board shall determine and designate only a bascule type of bridge. No part of such bridge or its approaches shall be suspended over such highway.