The Director-State Engineer, or such other officer who may have charge of such matters in this state, shall prepare plans, specifications, and estimates of the cost of construction, which shall be uniform throughout the state, and strain sheets and estimates of cost of all such standard pattern bridges, the estimated cost of which will exceed five hundred dollars each, as are best adapted to the requirements of the several counties; Provided, such plans, specifications, and estimates shall be based upon proper and sufficient data which shall be furnished to the secretary of the county board; and the Director-State Engineer shall supply the several counties with the number of prints of plans and strain sheets and printed copies of specifications, ordered by said counties, free of charge, and he shall retain all drawings in his office to be turned over to his successor.