The boards of supervisors of two adjoining counties may enter into an agreement with any person with whom such boards desire to collaborate for the purposes specified in section 1400, if such boards find that any of the following circumstances exist:
(a) That any bridge is necessary for highway purposes over any navigable body of water lying between such counties.
(b) That any existing bridge over any navigable body of water lying between such counties, and used wholly or in part for highway purposes, whether owned by either county or both counties, or used by either or both by agreement with the owner of the bridge, requires, in the interest of commerce or because of lack of repair:
(1) Reconstruction.
(2) Replacement by a new structure.
(3) Relocation at a place on such navigable body of water better suited to the use of the bridge or to the use of such navigable water.
(Enacted by Stats. 1935, Ch. 29.)