54 STAT.] 76TH CONG. , 3D SESS.-CH. 409-JUNE 21, 1940 approval, the bridge owner shall, in such manner as the Secretary may prescribe, take bids for the alteration of such bridge in accord- ance with such general plans and specifications. All bids, including any bid for all or part of the project submitted by the bridge owner, shall be submitted to the Secretary, together with a recommendation by the bridge owner as to the most competent bid or bids, and at the same time the bridge owner shall submit to the Secretary a written guaranty that the total cost of the project, including the cost of such work as is to be performed by the bridge owner and not included in the work to be performed by contract, shall not exceed the sum stated in said guaranty. The Secretary may direct the bridge owner to reject all bids and to take new bids, or may authorize the bridge owner to proceed with the project, by contract, or partly by contract and partly by the bridge owner, or wholly by the bridge owner. Upon such authorization and fixing of the proportionate shares of the cost as provided in section 6, the bridge owner shall, within a reasonable time to be prescribed by the Secretary proceed with the work of alteration; and the cost thereof shall be borne by the United States and by the bridge owner, as hereinafter provided. APPORTIONMENT OF COST SEC. 6. At the time the Secretary shall authorize the bridge owner to proceed with the project, as provided in section 5, and after an opportunity to the bridge owner to be heard thereon, the Secretary shall determine and issue an order specifying the proportionate shares of the total cost of the project to be borne by the United States and by the bridge owner. Such apportionment shall be made on the following basis: The bridge owner shall bear such part of the cost as is attributable to the direct and special benefits which will accrue to the bridge owner as a result of the alteration, including the expect- able savings in repair or maintenance costs; and that part of the cost attributable to the requirements of traffic by railroad or highway, or both, including any expenditure for increased carrying capacity of the bridge, and including such proportion of the actual capital cost of the old bridge or of such part of the old bridge as may be altered or changed or rebuilt, as the used service life of the whole or a part, as the case may be, bears to the total estimated service life of the whole or such part: Provided, That the part of the cost of alteration of any bridge for both highway and railroad traffic, attributable to the requirements of traffic by highway, shall be borne by the proprie- tor of the highway: Provided further, That in the event the altera- tion or relocation of any bridge may be desirable for the reason that the bridge unreasonably obstructs navigation, but also for some other reason, the Secretary may require equitable contribution from any interested person, firm, association, corporation, municipality, county, or State desiring such alteration or relocation for such other reason, as a condition precedent to the making of an order for such alteration or relocation. The United States shall bear the balance of the cost, including that part attributable to the necessities of navigation. PAYMENT OF SHARE OF THE UNITED STATES SEC. 7 . When the Secretary shall have approved the general plans and specifications for the alteration of such bridge and the guaranty with respect to the cost thereof, and shall have fixed the propor- tionate shares thereof as between the United States and the bridge owner, he shall furnish to the Secretary of the Treasury a certified copy of his approval of such plans and specifications and guaranty, 499 Recommendation of owner. Written guaranty of cost. Rejection, etc. Commencement of work. Determination and issuance of order. Basis for apportion- ment. Bridge owner. Provisos. Proprietor of high- way. Contributions from Interested persons, etc. United States to bear balance of cost. Setting aside of U.S . share by Secretary of Treasury.