1. With the approval of the appropriate state or local agency, a board may construct and maintain works and establish and maintain facilities, improvements or projects across or along any public street or highway, and in, upon or over any vacant public lands, which public lands are, or may become, the property of this State, and to construct works and establish and maintain facilities, improvements or projects across any stream of water or watercourse.
2. The board shall promptly restore any such street or highway to its former state of usefulness as nearly as may be, and shall not use the same in such manner as to impair completely or unnecessarily the usefulness thereof.