Each executive department, independent establishment, office, board, bureau, commission, authority, administration, corporation wholly owned or controlled by the United States, or other agency of the Government of the United States, hereinafter collectively and individually referred to as “agency”, which on or after July 29, 1946, has jurisdiction over and custody of any dam constructed or to be constructed and owned by or for the United States, is authorized, with any funds available to it, to design and construct any such dam in such manner that it will constitute and serve as a suitable and adequate foundation to support a public highway bridge upon and across such dam, and to design and construct upon the foundation thus provided a public highway bridge upon and across such dam. The highway department of the State in which such dam shall be located, jointly with the Secretary, shall first determine and certify to such agency that such bridge is economically desirable and needed as a link in the State or Federal-aid highway systems, and shall request such agency to design and construct such dam so that it will serve as a suitable and adequate foundation for a public highway bridge and to design and construct such public highway bridge upon and across such dam, and shall agree to reimburse such agency pursuant to subsection (d) of this section for any additional costs which it may be required to incur because of the design and construction of such dam so that it will serve as a foundation for a public highway bridge and for expenditures which it may find it necessary to make in designing and constructing such public highway bridge upon and across such dam. In no case shall the design and construction of a bridge upon and across such dam be undertaken hereunder except by the agency having jurisdiction over and custody of the dam, acting directly or through contractors employed by it, and after such agency shall determine that it will be structurally feasible and will not interfere with the proper functioning and operation of the dam.

Construction of any bridge upon and across any dam pursuant to this section shall not be commenced unless and until the State in which such bridge is to be located, or the appropriate subdivision of such State, shall enter into an agreement with such agency and with the Secretary to construct, or cause to be constructed, with or without the aid of Federal funds, the approach roads necessary to connect such bridge with existing public highways and to maintain, or cause to be maintained, such approach roads from and after their completion. Such agreement may also provide for the design and construction of such bridge upon and across the dam by such agency of the United States and for reimbursing such agency the costs incurred by it in the design and construction of the bridge as provided in subsection (d) of this section. Any such agency is hereby authorized to convey to the State, or to the appropriate subdivision thereof, without costs, such easements and rights-of-way in its custody or over lands of the United States in its custody and control as may be necessary, convenient, or proper for the location, construction, and maintenance of the approach roads referred to in this section including such roadside parks or recreational areas of limited size as may be deemed necessary for the accommodation of the traveling public. Any bridge constructed pursuant to this section upon and across a dam in the custody and jurisdiction of any agency of the United States, including such portion thereof, if any, as may extend beyond the physical limits of the dam, shall constitute and remain a part of said dam and be maintained by the agency. Any such agency may enter into any such contracts and agreements with the State or its subdivisions respecting public use of any bridge so located and constructed as may be deemed appropriate, but no such bridge shall be closed to public use by the agency except in cases of emergency or when deemed necessary in the interest of national security.

All costs and expenses incurred and expenditures made by any agency in the exercise of the powers and authority conferred by this section (but not including any costs, expenses, or expenditures which would have been required in any event to satisfy a legal road or bridge relocation obligation or to meet operating or other agency needs) shall be recorded and kept separate and apart from the other costs, expenses, and expenditures of such agency, and no portion thereof shall be charged or allocated to flood control, navigation, irrigation, fertilizer production, the national defense, the development of power, or other program, purpose, or function of such agency.

Not to exceed $65,000,000 of any money heretofore or hereafter appropriated for expenditure in accordance with the provisions of this title or prior Acts shall be available for expenditure by the Secretary in accordance with the provisions of this section, as an emergency fund, to reimburse any agency for any additional costs or expenditures which it may be required to incur because of the design and construction of any such dam so that it will constitute and serve as a foundation for a public highway bridge upon and across such dam and to reimburse any such agency for any costs, expenses, or expenditures which it may be required to make in designing and constructing any such bridge upon and across a dam in accordance with the provisions of this section, except such costs, expenses, or expenditures as would have been required of such agency in any event to satisfy a legal obligation to relocate a highway or bridge or to meet operating or other agency needs, and there is authorized to be appropriated any sum or sums necessary to reimburse the funds so expended by the Secretary from time to time under the authority of this section. Of each bridge constructed upon and across a dam under the provisions of this section, there may be financed wholly with Federal funds that portion thereof which is located within the physical limits of the masonry structure, or structures, of the dam, and the Secretary shall in his sole discretion determine what additional portion of the bridge, if any, may be so financed, such determination to be final and conclusive. The remainder of the bridge, and any necessary related approach roads, shall be financed by the State or its appropriate subdivision with or without the aid of Federal funds; but said portion of the bridge so financed by the State or its subdivisions, including such portion thereof, if any, as may extend beyond the physical limits of the dam, shall nevertheless be designed and constructed solely by the agency having custody and jurisdiction of the dam as provided in subsection (a) of this section.

In making, reviewing, or approving the design of any bridge or approach structure to be constructed under this section, the agency shall, in matters relating to roadway design, loadings, clearances and widths, and traffic safeguards, give full consideration to and be guided by the standards and advice of the Secretary.

The authority conferred by this section shall be in addition to and not in limitation of authority conferred upon any agency by any other law, and nothing in this section contained shall affect or be deemed to relate to any bridge, approach structure, or highway constructed or to be constructed by any such agency in furtherance of its lawful purposes and requirements or to satisfy a legal obligation incurred independently of this section.