Mt Henry Bridge
The north-south freeway system, which provides for the bypassing of the Perth central business district, was planned and developed by Professor G. Stephenson and Mr. J. A. Hepburn in 1955. Apart from the completion in 1959 of The Narrows Bridge, which connects the north and south banks of the Swan River, the whole Freeway plan was adopted by the WA State Parliament in 1963. There have been amendments made to the plan on a number of occasions, brought about by changing demands and following further studies.
The first stage of the southern extension of the road, designated The Kwinana Freeway, saw the completion of the Canning Interchange in 1979. The second stage saw the extension reach South Street, when it was officially opened on 9 May 1982. This included the construction of the Mt. Henry Bridge across the Canning River and its completion, following 34 months of work, in April 1982. When completed, the bridge was (and still is) the longest road bridge in Western Australia, being 688 metres in overall length (including abutments) and 28.8 metres in width.
It accommodates 6 lanes of traffic with a central concrete median barrier. It consists of nine continuous spans of precast, double-cell, single box, post-tensioned, concrete segments, supported by sculptured reinforced concrete piers. There are 7 spans of 76.25 metres and 2 end spans of 63 metres.
An unusual feature of the bridge was the provision of a 3.15 metre pedestrian walkway and cycleway cantilevered from the bottom flange of the superstructure, on each side. The bridge was designed by the Main Roads Department of Western Australia and constructed by the Clough Engineering Group. Construction on site commenced on 31 May 1979 and contractual completion was 24 April 1982. Not a single hour of work was lost through industrial unrest caused by site working conditions or disagreements.The Safety record was very good, with no major incidents recorded, and the percentage of hours lost was 1.07% from some 380,000 hours worked.
