The original Tasman Bridge across the Derwent River, which the
current bridge replaced, was a unique floating bridge which was opened
in 1943. By 1955, constant damage to it by storms and high seas and its
inability to handle the increased traffic using it led the Tasmanian
Government to build a replacement.
That replacement, Tasman Bridge, today links the city of Hobart to the
suburbs on the eastern shores of the River Derwent. As the water to be
spanned by the bridge would span was close to 50% wider than the
channel spanned by the Sydney Harbour Bridge, yet needed to be as high
as that bridge to allow the passage of medium sized cargo vessels, it
was decided to build a bridge supported by a series of piers supporting
nineteen spans, with a single navigation span over the deepest part of
the river, which would be the apex of the bridge. Allowing for a span
width of 42.7 metres, the bridge would have 13 spans to the west of the
navigation span and 6 to the east.
The major part of the bridge is founded on either basalt or dolerite at
depths up to 160 feet below water level. Beneath Piers 4 to 8, the
dolerite is as much as 300 feet below water surface and is overlaid by
very stiff clays, a thin layer of coarse gravel and shingle, very stiff
sandy loam and conglomerate. The underside of the central navigation
span is around 48 metres above mean water level.
Construction commenced in May,1960 and the bridge was first opened to
traffic (2 lanes only) on 18th August, 1964. By 23rd December, all four
lanes became operational. The first ship to pass under bridge, Galway,
did so on 18th August 1964. During peak construction a labour force of
over 400 men was employed on site. The total cost of the new Tasman
Bridge together with approach roads and Lindisfarne interchange was in
the order of £7 million.
Tasman Bridge Disaster
On the evening of Sunday, 5th January, 1975 at 9.27 pm, the bulk ore
carrier "SS Lake Illawarra" loaded with zinc concentrate, drifted out
of the main navigation lane and collided with the Tasman Bridge. Two
piers collapsed along with 127 metres of decking. It was drizzling and
after dark, so visibility was poor. Bridge traffic kept coming over the
rise in the bridge and hurtling into the river below. One driver became
aware of the collapsed span. He stopped his car and tried to warn
others, but most of them took no notice and kept going to their deaths.
Four cars ran over the gap into the Derwent, five occupants died, while
several others managed to escape from their vehicles which were hanging
on the edge of the gap. Seven crewmen from the "SS Lake Illawarra" also
lost their lives.
The impact of the bridge collapse was quickly felt as Hobart was
suddenly cut in two. Eastern shore residents were severely compromised,
transport facilities were tested and to compound the issue further,
most hospitals, schools, businesses and government offices were located
on the western shore. By the next day, three private ferries and a
government vessel were in operation. Health services also needed to be
addressed and within four months most of the essential services needed
by Clarence residents had been provided.
Weeks after the collision a decision had been made to construct a
temporary bridge north of the damaged Tasman Bridge, in order to
restore a direct road link between Hobart and the eastern shore. The
Bailey Bridge was opened to traffic on 16th December 1975. It provided
one lane of traffic each way on a temporary structure crossing at
Immediately after the Bridge collapsed, the Federal and State
Governments set up the Joint Tasman Bridge Restoration Commission to
direct the reconstruction of the Bridge. Specialists in the marine
engineering field undertook an extensive investigation to locate bridge
debris. This survey took a number of months to complete, and parts of
the bridge weighing up to 500 tonnes were located to an accuracy of a
few centimetres, using equipment developed by the University of
Tasmania and the Public Works Department.
Maunsell and Partners were appointed consultants for the rebuilding
project. John Holland Contractors were awarded the contract. The
Federal Government funded the project which began in October 1975.
Engineers decide not to replace pier 19 as there is too much debris on
the site, and so only one pier was replaced and two spans of the three
spans that were brought down in the collision were replaced by a
single, new span. The Tasman Bridge was initially designed to carry
four lanes of traffic, however prior to the disaster, heavy demands had
been placed on the bridge during peak times. It was decided to widen
the bridge as part of the reconstruction works to carry five lanes of
traffic. The Bridge took about two years to re-build at a cost of
approximately $44 million, which was around three times its initial
cost thanks to inflation. The Tasman Bridge was officially re-opened to
the public on Saturday 8th October, 1977.