33 U.S. Code § 516 - Apportionment of cost
At the time the Secretary shall authorize the bridge owner to proceed with the project, as provided in section 515 of this title, 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 expectable 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:
1958—Pub. L. 85–640 permitted issuance of an order of apportionment of cost for entire alteration based on the accepted bid for first part of alteration and an estimate of cost for remainder of work where bridge owner proceeds with alteration on a successive partial bid basis.
1952—Act July 16, 1952, made railroads share equally with proprietors of highways in bearing cost of alterations necessary to remove obstacles to navigation.