A tale of five bridges

The River Derwent Crossing between Granton and Bridgewater has a long history, with  successive bridges built over the years that allowed for safe passage across this section of the river.

The idea of a bridge was envisioned to complete the link across the river that the 1836  Causeway had started. The Causeway had been chosen over earlier suggestions for a timber  beam bridge, and ran from the river’s southern bank as far as a deep channel towards its
north bank, due to the need for ships to sail through and provide transport for people and  resources throughout the colony. This final section from the end of the Causeway to the shore  at Bridgewater was crossed by a punt (a cabled-ferry), but a more permanent solution was still  required.

The construction of the modern Bridgewater Bridge was the largest transport infrastructure project in Tasmania’s history at the time of completion. The construction company McConnnell Dowell built the new bridge, in accordance with the design requirements of the Tasmanian Government.

The bridge was required to provide a navigable clearance for boats consistent with the Bowen Bridge, two lanes in each direction, a shared path for pedestrians and cyclists and a minimum design speed of 80km/h.

For the first time in 175 years, the Bridgewater Bridge provides for the movement of larger boats up and down the River Derwent, without the requirement to stop bridge traffic.

Bridge One - Timber Rolling Span Bridge (1849)

The first Bridgewater Bridge began construction in 1847, and was designed by James Alexander Thompson and James Blackburn.

The bridge deviated slightly eastwards at a 180-degree angle from the end of the Causeway.

The structure was made of timber beams built on timber piles, with an ingeniously designed rolling span that moved on iron wheels along rails, controlled by hand winches.

This mechanism allowed a 23 metre section of the bridge to roll open and create a 11m gap for ships and vessels to travel through.

To accommodate this retracted section of the bridge, the timber deck behind it was split lengthwise into two sections that could be moved out of the way by a system of wheels and winches.

The centre of the bridge was supported by a four-columned tower with chains suspending either end of the rolling section.

The bridge was completed in 1849, with a toll-house collecting fares.

By 1880 this first bridge was still in operation, acting as the only traversable road passage across the river. However in the 1890s, travel across the bridge was banned as it was deemed to be unsafe due to deterioration and poor condition, but without an alternative it was still used by many.

The bridge survived alongside Bridges Two and Three for nearly 30 years until it was finally demolished in 1899.

Bridge Two Swing - Span Rail Bridge (1874)

When Tasmania’s railway system was introduced in the 1870s, it was quickly apparent that a river crossing was required to connect Hobart and Launceston.

The logical choice for this rail crossing was the existing Bridgewater Causeway, which to fit the new railway line had to be widened alongside the existing road.

The new rail bridge, completed in 1874, would turn eastward from the end of the Causeway, running roughly parallel to the 1849 bridge and reaching the northern bank of the river about 15 metre downstream of the first bridge.

Due to the advances in technology in the 1840s, this new bridge utilised a swing span system involving a steel lattice girder section that could twist open on a turntable, operated using hand winches.

Unlike many other swing bridges, the swinging span was positioned asymmetrically, with the southern half being considerably longer to allow for a larger opening, and to reduce the total length of the supporting truss. A tow path was installed in the middle of the opening that would guide boats between the openings of the two bridges avoiding any collisions.

In 1886 a locomotive derailed on the bridge, after the span rotated several degrees. A fireman and a passenger were killed in the incident, which prompted an investigation into the operation of the bridge.

This second bridge would survive for nearly 70 years, much longer than expected. However it required a large amount of upkeep and maintenance as it aged, and was eventually replaced by the Bridge Three in 1907, and finally demolished in 1942.

The bridge abutments constructed for the 1874 bridge still remain today on the northern end of the Causeway and the opposite, southern bank of the Derwent.

Bridge Three - Swing Span Road Bridge (1893)

The earlier Timber Rolling Span Bridge (Bridge One) completed in 1849 operated for more than 30 years as the only road link across this section of the River Derwent. By the 1880s it was in increasingly poor condition, and was deemed too dangerous for use in 1888.

In the early 1890s construction began on a new bridge to replace the now unusable Timber Rolling Span Bridge.

This new bridge was designed to extend straight out from the end of the Causeway to reach the other side of the bank, 20 metres upstream from the previous two bridges which curbed east sightly. It was designed with a swing span mechanism, alongside a five metre wide section rotating open to allow ships and boats to travel through it.

The swing span itself was made of heavy girders and was supported by a riveted steel, concrete filled cylinder built into the riverbed.

While Bridge Three was intended to serve motor traffic, it was designed to allow for an inevitable conversion into a rail bridge. While this conversion was intended to happen soon after its construction in 1893, it did not proceed until 1905 when Bridge Two, now 30 years old, was significantly deteriorating, necessitating a new rail crossing.

The conversion of this bridge would require even more widening to the Causeway, completed in 1907, with the first trains crossing in 1908.

Unfortunately, while the two earlier bridges allowed for separate crossings for motor cars and trains, the 1908 conversion of Bridge Three only allowed for a train to cross when all motor traffic had been cleared.

This was extremely inefficient and unpopular, with constant traffic delays made worse by the opening of the swing span that allowed boats to cross. To alleviate this, Bridge Two was refurbished and upgraded into a new road crossing in 1908 remaining in place until 1942.

For more than 50 years Bridge Three continued to be the only rail crossing, eventually demolished in 1946 after the completion of another bridge that would replace it.

The concrete support cylinder, known as a ‘caisson’, can still be seen, half-submerged in the River Derwent, and the 1893 bridge’s northern and southern abutments are still visible on the riverbank and at the end of the Causeway.

If you’re travelling down the Brooker Highway though Derwent Park, you can still see the girder’s used in the bridge’s rotating swing span, being used as part of a rail and walking bridge over the highway.

Bridge Four - Lift Span Bridge (1946)

Construction of the fourth Bridgewater Bridge began in the late 1930s, but was put on hold due to the outbreak of the Second World War in 1939.

It was traversable for small amounts of motor traffic in 1942, with the complicated lifting span mechanism being installed in 1946 after the war ended.

Bridge Four was by far the largest and most mechanically advanced of the Bridgewater Bridges, utilising a lift span system in which the 42.9 metre central part of the bridge could be raised up supported on either end by two 40 metre high span towers, creating a 36.5m wide opening for water craft to travel through.

The central lift span and supports were constructed from strong, lightweight trusses, while the lift span is topped with a lightweight timber deck weighing around 350 tonnes.

The two towers that support the lifting system are reinforced with concrete piers sitting on timber piles in the river. These piers supported the two towers that would lift the central span, counterbalanced with large concrete weights attached to six 44 millimetre wire ropes that passed over a large sheave, or pulley wheel, located on top of the two towers.

This pulley system allows the lift to be pulled up and down and is operated by a powerful twin wound rotor electric motor with a diesel backup engine.

This bridge is recognised as an important landmark for the region, carrying more than 22,000 vehicles a day, renowned for its engineering ingenuity and significance, as well as being the one of longest lasting lift span bridges in Tasmania, lasting for more than 80 years.

Despite this, like the many bridges before it, Bridge Four has undergone significant deterioration, including decaying concrete, sinking support piles, unprecedented stress damage on the counterweight ropes, as well as various other maintenance issues which became more and more frequent.

By 2019, the bridge was reaching the end of its life and the project to construct a replacement began. The existing bridge is scheduled to be demolished in 2025, following the completion of the new bridge, which will sit further downstream.

While the fourth bridge itself will be removed and the Northern Tower arch relocated to the foreshore, several sections of the bridge will remain in their existing locations to highlight the history of the bridge’s development.

These remaining features include the North and South bridge abutments on the foreshore and end of the Causeway, as well as three of the northern and southern concrete support pillars (caissons) for the bridge.

Sections of the bridge will also be repurposed to produce an outdoor contemporary sculpture that will be installed in the Bridgewater foreshore.

Video depicting Bridge Four's lift operations.

Bridge Five - 2025 The New Bridgewater Bridge

The new Bridgewater Bridge represents a significant milestone in Tasmania’s infrastructure history, marking the fifth bridge constructed at the vital River Derwent crossing since 1848.

Opened in June 2025, the bridge was designed to meet the needs of a growing population while honouring the legacy of those who came before, the new bridge reflects a commitment to preserving the cultural, historical and engineering heritage of the region.

The new bridge acknowledges the long-standing significance of the crossing to local communities and industry, ensuring that its story continues for future generations.

References:

• Ian D. Cooper, 2018. ‘Bridgewater Bridge Tasmania: Nomination for Engineers Australia Engineering Heritage Regoniction.’ Prepared for Department and Infrastructure Tasmania and Engineering Heritage Tasmania, p. 8 Fowler, A
• ‘River Derwent, Tasmania – Bridgewater Bridges – Past and Present’, 2011 Smith R, ‘early Tasmanian bridges’, Foot and Playsted
• 1969 Whitham L, ‘the bridges, roads and rails of Bridgewater’
• 1989 Newitt L, ‘convicts and carriageways’, Tasmanian Government Printer
• 1988 O’Connor C, 1997, ‘bridge and causeway engineering Bridgewater heritage assessment’, P27
• Unknown writer, ‘The Illustrated London News’, 12 April 1851,
• P288 Pitt & Sherry, ‘national highway approach to Hobart, Bridgewater Bridge planning study”,
• 1999 Jordan, Nevard and Stewart, ‘Bridgewater crossing of the Derwent River,
• The Midland Highway and national highway approach to Hobart, panel report on heritage, landscape & transport aspects of the Bridgewater crossing’, 2002
• New Bridgewater Bridge Project Heritage impact statement, Purcell, 2021