Tasmania in Photographs: Construction of Pontoon Bridge

Unattributed photographs of the construction of the Hobart Pontoon Bridge in 1943 from a booklet published by OLDHAM, BEDDOME & MEREDITH PTY. LTD. HOBART and printed by Pilven & Stephens, Melbourne: Wartime Production.

The bridge was dismantled in 1964.

Foreward by A.W. Knight Esq Chartered Engineer:

"THE HOBART BRIDGE

The Publishers of this little book of views of the Hobart Bridge have invited me to write a short foreword to the publication.

The bridge across the Derwent River at Hobart, Tasmania is of unique construction, being the first of its type anywhere in the world. The major portion of the bridge is a floating concrete structure curved upstream in the form of an arch. It is this feature which enables it to withstand the forces of wind and current without the anchors generally used to hold more orthodox forms of floating bridges in position.

The design of the bridge was conceived by the writer in 1936. In 1936 the Government of Tasmania, which had at that time as its Premier the late Honourable A. G. Ogilvie, K.C., passed an Act authorising a Company to construct the bridge to the design and under the supervision of officers of the Public Works Department, and to operate the bridge as a toll structure.

Construction was commenced in April, 1938, by Timms Bridge Construction Co. Pty. Ltd., Contractors to the Hobart Bridge Company Ltd., and the bridge was opened for traffic in December, 1943. On 4th December, 1943, shortly before the bridge was opened for traffic, it was tested by a very severe southerly storm. Since that date certain measures designed to increase the strength of vital parts of the bridge have been carried out, and others are under consideration. There is good reason to believe that these measures will prove effective.

The building of this bridge has proved a major task, and is the outcome of the joint efforts of those concerned in the spheres of politics, business and engineering. In the political field, the late Honourable A. G. Ogilvie, K.C., played a vital part, and, since his lamented passing, the Honourable Robert Cosgrove has been responsible as head of the Government.

H. S. Barnett, Esquire, carried out all the early negotiations for the construction of the bridge, and was responsible for arranging the necessary finance and the insurance, and, when the Hobart Bridge Company was formed for the purpose of constructing the bridge, Mr. Barnett was appointed the Company's Managing Director. The results of his enterprise and ability speak for themselves.

The other Directors of the Hobart Bridge Company are:-E. M. Johnson, Esq., K.C.; R. A. Chandler, Esq.; C. H. Grant, Esq.; Edney P. Moore, Esq.; and H. E. Coleman, Esq. H. H. Cummins, Esq., is Secretary.

One of the features of particular interest is the fact that the bridge was insured by the leading British Marine Insurance Companies and by Lloyds of London, and, following the storm of 4th December, 1943, the Hobart Bridge Company Ltd. was paid an amount of £250,000 by the Insurers in accordance with the terms of the contract of insurance.

The major portion of the funds required for the bridge undertaking were provided by the City Mutual Life Assurance Society Ltd. in the form of a loan to the Hobart Bridge Company Ltd. The balance was provided by shareholders of the Bridge Company. The Government of Tasmania constructed the road approaches for the bridge and has assisted in various other ways, including a loan of £31,000 towards the extra costs of the main abutment.

The cost of the undertaking to the Hobart Bridge Company was in the vicinity of £500,000.
The annual cost of the bridge to cover charges for interest, maintenance, operation and depreciation, amounts to approximately £30,000. This compares with a figure of £77,000 per year for the approximate cost of an orthodox typo of structure on the same site.

The late C. D. Timms, Esq., was Manager for the Contracting Company with F. H. Wood, Esq., as Chief Engineer. Following reorganisation of that Company, G. Leitch, Esq., B.C.E., became Engineer for the Contractor.

The design, plans and supervision of construction of the Bridge was the responsibility of the public Works Department of which G. D. Balsille, Esq., M.I.C.E., M.I.E. Aust., is Director; and the writer is Chief Engineer; D. V. Isaacs, Esq., M.C.E., was Consulting Engineer to the Department; J. A. Slatter, Esq., B.C.E., was Resident Engineer; and C. E. L. Knight, Esq., B.Sc., Surveyor.

The passing of the necessary legislation, the formation of the Hobart Bridge Coy. Ltd., the financing and the building of the bridge spread, over a period of eight years, has involved a tremendous amount of detailed work on the part of all concerned. Voluminous calculations have been made, hundreds of sheets of plans prepared and these plans translated info reality. The floating portion of the bridge alone weighs 25,000 tons, and every pound of this material has been handled by human hands, not once but many times. The two main sections of the floating arch, each more than fifteen hundred feet long, were built in a curve to an accuracy of a fraction of an inch. These were constructed two miles from the bridge site, then towed to the final position and attached to previously constructed anchorages by steel pins which fitted bearings with a clearance of a few thousandths of an inch.

The Lift Span, which weighs three hundred and fifty_ tons, lifts to its full height 150 feet above wafer level in less than 2 minutes. It is balanced by concrete counterweights so that the total moving weight is seven hundred tons. The span is operated with great precision by automatic equipment which reduces hazards to a minimum.

These things are not achieved by chance. They are the result of years of labour by engineers, by surveyors, by draftsmen, tradesmen, by workmen and those engaged on administrative tasks.Their labour has not been in vain, and Tasmania now possesses a public utility that was first mooted more than a hundred years ago.

(A.W.KNIGHT Chartered Engineer)"

The fate of the pontoon bridge?

Wikipedia provides this brief account:

The bridge was opened to toll traffic on 22 December 1943 and the collection of tolls continued until midnight on 31 December 1948. Soon after its opening a violent storm blew in and damaged a section of the bridge, and to prevent the same happening again, the bridge was anchored to the riverbed in the middle and strengthening cables were added to stiffen the structure. After these modifications were completed the lifespan of the bridge was estimated as 21 years.

The bridge provided much better connection between the Eastern and Western Shores, and consequently development on the Eastern Shore sped up and became so dense by the mid-1950s that the floating bridge could no longer handle the amount of traffic that was crossing it. Congestion became a severe problem, and in the late 1950s the decision was taken to construct a completely new bridge, the Tasman Bridge, which opened in early 1964.

The floating bridge was closed to traffic on 17 August that year, and the following day the locking pin was removed and the two concrete sections towed away. For several years they were moored, but one of them sank in November 1970, and the Council undertook to dispose of them. The two halves were cut up and sunk at various locations. The lift span was left in situ for some years but in the end it too was demolished. Today the only reminders of the bridge are the eastern foot of the lifting section which is still in place, and the preserved locking pin. One of the pontoons was sunk at Allonah, and remains in use as a public jetty.