(1) The department may, through its own engineers, design and build bridges either with its own employees or by contract, and pay for the construction thereof out of the funds derived from the sale of bonds. No bridge shall be built by the department with its own employees, except after advertising for bids and the reception and rejection thereof as is provided for the construction of primary roads and subject to the further provisions of this chapter as to advertising.
(2) No officer or employee of the department shall have any interest in or association, either direct or indirect, with any person or association having any interest in building or acquiring any bridge or in the sale or purchase of any bond authorized by this chapter.