As a consequence of opposition from the proprietors of the Mersey and Irwell Navigation, it had been intended to terminate the railway on the Salford side of the Irwell. A last minute agreement brought about a change in plan. The river would be spanned by a two arched stone bridge, incorporating a cart road for the use of the Navigation company. The real problem was how to cross Water Street. The levels would not permit an arched bridge to the dimensions demanded by the Manchester Highway Commissioners. The only alternative was a flat span across a distance judged to be too wide. William Fairbairn, in the quest to perfect fireproof mill flooring, had developed a parabolic 'T' section girder that could span such a distance. Thus, the Water Street bridge might be said to be the first modern girder bridge.