Whenever it is ordered by resolution of the board that any county road shall be laid out and established and altered, widened, or otherwise constructed or improved, the county road engineer employed by the county shall prepare such maps, plans, and specifications as shall be necessary and sufficient. A copy of such maps, plans, and specifications shall be approved by the board of county commissioners with its approval endorsed thereon, and such copy shall be filed with the clerk of the board.
RCW 36.77.010