The department, through its own engineers or through such other engineers or experts as it may employ, shall design all bridges, transportation facilities, and additional transportation facilities to be built pursuant to this chapter, and may build them or any portions of them either by its own employees or by contract with any person. The cost of any or all such bridges, transportation facilities, and additional transportation facilities shall be paid from the proceeds of bonds issued and sold pursuant to this chapter, or from contributions or appropriations from other sources as provided in this chapter.