Tasman Bridge

History

During the 1950s, Hobart's eastern shore underwent substantial expansion due to the opening of the Hobart Airport at Cambridge in 1956. By 1957, the airport was the country's fifth busiest, and the surge in air travel, associated automobile usage and surrounding developments led to a notable rise in traffic, overwhelming the capacity of the existing Hobart Bridge. With its single carriageway struggling to manage escalating traffic volumes and frequent disruptions due to the lifting of the bridge's lift span for passing ships, a necessity emerged for a novel bridge solution. These challenges highlighted the pressing need for a new, more accommodating bridge designed specifically for the increased traffic flow without constant interruptions for maritime navigation.

Design

In 1956, Tasmania's Department of Public Works commissioned Maunsell & Partners Pty Ltd to design the new River Derwent crossing. The stable foundation for the bridge was ensured by the favorable conditions of the riverbed between Queens Domain and Montagu Bay on the eastern shore, which includes bedrock, dolerite, and basalt beneath the silt. The engineers recommended a bridge supported by multiple piers due to the width of the water expanse, similar to that of the Sydney Harbour Bridge but requiring a comparable height to accommodate medium-sized cargo vessels. Consequently, a decision was made to construct a girder bridge featuring twenty-two spans, including a navigation span at its apex, with thirteen spans to the west and six spans to the east, each measuring 42.7 meters wide. To achieve the height of the 60.5 m apex, a large sequence of interval spans was critical in the design to accommodate the weight of concrete required for each heightened pier, with its deepest pile measuring 265 ft below mean sea level.

Criticism of Premier Eric Reece arose in 1958 when concerns were raised by engineers about the susceptibility of the concrete design to potential ship collisions. Investigative reports revealed Reece's dismissal of objections during parliamentary proceedings in favor of the $14 million project over a slightly more expensive suspension bridge option.{{Citation | title=Second Hobart Bridge: report on Tasman bridge, risk of ship collision and methods of protection, September 1978 | author1=Maunsell & Partners | author2=Brady, P. J. E | author3=Joint Committee on Second Hobart Bridge | author4=Tasmania. Department of Main Roads | year=1978 | publisher=Department of Main Roads, Tasmania | isbn=0-7246-0916-4 | url=https://nla.gov.au/nla.cat-vn2893310 | access-date=21 November 2023 |language=English

The bridge was originally built to a design life of about 100 years.

Construction

Tenders were issued in April 1959, and contracts were subsequently awarded to Reed, Braithwaite, Stuart, and Lipscombe in November of the same year. Construction on the eastern shore viaduct commenced in May 1960. A labour force of over 400 workers were employed during peak construction.

Several prerequisites were crucial during construction. The old Hobart Bridge had to remain operational until the Tasman Bridge's completion, and shipping lanes along the River Derwent needed to stay open. The construction posed significant challenges for Hobart as it marked the city's largest and most expensive undertaking to date. Procuring construction equipment, such as jacks and wires, required sourcing from the UK, while reinforced steel had to be imported from the Australian mainland, contributing to the bridge's elevated cost, totaling £7 million, equivalent to $14 million in 2015.

The first two lanes bridge opened on 18 August 1964. The other two lanes opened on 23 December 1964. It was officially opened on 29 March 1965 by Prince Henry, Duke of Gloucester. Upon completion, the Tasman Bridge was the longest prestressed concrete bridge in Australia, utilising 45000 lt of concrete and 5200 lt of reinforcement steel.

Disaster

Main article: Tasman Bridge disaster

On 5 January 1975, the SS Lake Illawarra, a 140 metre bulk ore carrier, collided bow first with the pile capping of Pier 19 and then amidships with Pier 18 while en route to EZ Industries' Risdon Zinc Works with a cargo of 10000 tonnes of zinc concentrate.

The breakage of an important arterial link isolated the residents in Hobart's eastern suburbs – the relatively short drive across the Tasman Bridge to the city suddenly became a 50 km journey via the estuary's next bridge at Bridgewater. The only other vehicular crossing within Hobart after the bridge collapsed was the Risdon Punt, a cable ferry which crossed the river from East Risdon and Risdon, some 5 km upstream from the bridge. It was totally inadequate, carrying only eight cars on each crossing, and although ferries provided a service across the river; it was not until December 1975 that a two lane, 788 m bailey bridge was opened to traffic, 2 km to the north from Dowsing Point to Cleburne Point thereby restoring some connectivity. The bailey bridge remained in use until replaced by the Bowen Bridge in 1984.

The separation of Hobart saw an immediate surge in the small and limited passenger ferry service then operating across the river. He had introduced the locally-built ferries Matthew Brady and James McCabe to the river crossing, from the Hobart central business district to the eastern shore, shortly before the collision. These were soon joined by the , a wooden vessel of 1912 vintage, and Kosciusko, Lady Ferguson and Lady Wakehurst that were loaned by the New South Wales Public Transport Commission.

Following the Tasman Bridge Disaster, former-Premier Eric Reece maintained his defence of the chosen bridge design. Reece argued that the selected design was the sole financially viable option for the state at that time, despite the construction costs doubling throughout the project's execution.

Reconstruction

Reconstruction of the Tasman Bridge by John Holland commenced in October 1975. Due to the amount of debris at the foundations, engineers decided not to rebuild Pier 18. Pier 17 on the western side of the gap was reinforced, and the pile cap and shaft of the pier above water level were replaced. A new pier was built at the site of the decimated Pier 19, and the existing Pier 20, on the eastern side of the gap, was repaired and strengthened. A new span, about 85.5 m long, was built in steel box girder construction between piers 17 and 19, and another new, prestressed concrete span, about 42.5 m meters long, was built from the new Pier 19 to Pier 20.

The annual expenditures on the Tasman Bridge reconstruction were $1.7 m in 1974–75; $12.3 m in 1975–76; $13.2 m in 1976–77 and $6.1m in 1977–78. After two and half years and an approximate cost of $44 million, the Tasman Bridge reopened to the public on 8 October 1977.

Following the reopening of the bridge, the Port of Hobart implemented additional maritime safety measures, including directing large vessels to navigate slightly west of the original main navigation span and providing specialised training to harbour pilots in the use of a laser lighthouse for navigation. Additionally, the City of Hobart configured traffic systems to temporarily halt all road traffic when large vessels approach and pass under the bridge.

Wreck of SS ''Lake Illawarra''

The average depth of the river between piers 17 and 19 is 35 m, with the wreck of the SS Lake Illawarra lying on the bottom covered by a scattering of concrete debris, presenting no navigational hazard to smaller watercraft. 10000 tonnes of zinc concentrate remain in the vessel's cargo hold.

The wreck attracts regular visits from divers. In 2019, the Tasmanian University Dive Club shared underwater footage of the wreck on social media. This footage, championed as the clearest footage ever captured, was attributed by the Derwent Estuary Program to decreased sediment levels in the River Derwent, a result of improved stormwater management measures in the city.

In 2022, the CSIRO and Jacobs Engineering Group collaborated to produce the first complete 3D model of the wreck, bridge, riverbed, and shoreline. The mapping unveiled the ship's placement adjacent to the bridge between piers 17 and 19 on the eastern shore, with its bow near Pier 19, angled at 45 degrees toward the centre of the river. The vessel's bow lies roughly 15 m below the waterline, around 125 m from the eastern shore.

Upgrades

Addition of fifth lane

The bridge deck was widened to accommodate a fifth traffic lane during the bridge's 1975 reconstruction. Utilising a Japanese construction method dubbed the "Nippon clip-on," the central lane incorporates a reversible lane management system for tidal flow operations.

Tidal flow operations

Designed to optimise vehicle flow throughout the day, the reversible lane operates with a traffic light system and a sign above each lane. These signs, working in tandem with the traffic lights, utilise a pulley system to periodically shift over their respective lanes. During morning peak hours, the middle lane directs traffic towards the city side (or western shore), while during evening peak hours, it points back towards the eastern shore. Outside of peak hours, the lane generally directs traffic towards the eastern shore. This adaptable lane configuration maximises the bridge's capacity and reduces congestion by efficiently utilising lanes according to current traffic demand.

LED lighting

In 2019 the Hobart City Council commissioned Decrolux to convert the Tasman bridge's fluorescent lighting with modern LED lighting. Spanning almost 3 km and utilising 1,930 LEDs, the project was completed in 2021. These remotely programmable lights have been utilized for various purposes, including commemorating annual events such as Dark Mofo and the TasPride parade, supporting sports teams like the Hobart Hurricanes and Tasmania JackJumpers, marking special occasions like the inauguration of Queen Mary of Denmark, and raising awareness for causes such as Women's Health Week and Men's Health Week.

Sensors

In 1987, a system of sensors to monitor river currents, tidal height and wind speed was installed by the authorities in the navigation channel beneath the bridge, to assist vessel movements in the vicinity.

2020s refurbishment

In June 2022, the Tasmanian transport ministry announced a investment in the Tasman Bridge: the largest since its 1977 reconstruction. Designed by GHD Group with a target completion date set for 2025, the project includes wider dedicated paths for cyclists and pedestrians, higher barriers separating vehicles and pedestrians, upgraded lighting, and digital signage. In September 2024, the Tasmanian Government announced that it had scrapped plans to widen the shared pathway, though it would proceed with installing new barriers and passing bays.

Gallery

Tasman-under-from-east-shore.jpg|Tasman Bridge from the eastern shore Tasman-bridge-from-south.jpg|Looking towards the Tasman Bridge from Montagu Bay NS14TasmanBridge.JPG|Dinghy and the bridge Tasman Bridge Hobart1.jpg|Tasman Bridge from Mount Wellington Derwent River 013.jpg|A view of the bridge from the river Tasman Bridge from Western shore.JPG|Tasman Bridge from the Western shore Bridge into Hobart.jpg|Entering the bridge from the eastern shore Tasman Bridge towards Rose Bay, Hobart, Tasmania (36103737153).jpg|Entering the bridge from the west side

Notes

References

Sources

References

1. Department of State Growth. (2019). "Department of State Growth Key Arterials Traffic Data Catalogue".
2. (2015-03-28). "Tasman Bridge: 50th anniversary of official opening".
3. (2010). "Cycling South Tasmania – Tasman Hwy and Bridge".
4. (2002). "Tasmanian Year Book, 2000". [[Australian Bureau of Statistics]].
5. Whelan, Janet. "Aftermath, the Tasman Bridge Collapse: criminological and sociological observations". Australian Institute of Criminology.
6. "Tasman Bridge Disaster".
7. Gwynn, Liz. (19 May 2022). "SS Lake Illawarra mapped in 3D as government prepares to upgrade Tasman Bridge".
8. (27 June 2022). "Designs released for $130m upgrade of Hobart's Tasman Bridge".
9. Dearing, W.. (2020-09-01). "Hobart International Airport – A Brief History".
10. "Our history".
11. "Opening of the Tasman Bridge".
12. "Tasman Bridge Pathways Upgrade".
13. (28 November 1959). "New £4m. Bridge For Derwent". [[The Canberra Times]].
14. Giant Bridge Opened ''[[Truck & Bus Transportation]]'' September 1964 page 109
15. Tasman Bridge ''[[Australian Transport]]'' October 1964 page 27
16. (2022-03-28). "Dividing Impact: The Tasman Bridge Collapse". Brick Immortar.
17. (2000). "Bridge gone". Tasmanian Government.
18. Hobart's Temporary Bridge ''Australian Transport'' April 1976 pages 34/35
19. Hobart ''[[Transit Australia. Electric Traction]]'' May 1984 page 93
20. [https://trove.nla.gov.au/newspaper/article/110632428 New terminals for ferries on three weeks] ''Canberra Times'' 11 January 1975 page 1
21. A Friend in Need ''[[Transport News]]'' March 1975 page 3
22. (4 June 1975). "1977 date for bridge". [[The Canberra Times]].
23. "Tasman Bridge Disaster - City of Clarence: City of Clarence". [[City of Clarence.
24. MacDonald, Megan. (2019-10-22). "Wreck of Lake Illawarra, which struck the Tasman bridge, shown in new underwater footage".
25. Marrison, Matthew. (2022-05-20). "New technology lights up the location of SS Lake Illawarra".
26. "Visions of the Derwent's Eastern Shore: a pictorial compilation". John Sargent.
27. The Roads ''Australian Transport'' October 1978 page 6
28. "Tasman Bridge Lighting Upgrade".
29. "Tasman Bridge, from collapse to reconstruction".
30. Sutherland, Isla. (30 June 2022). "Plans released for Hobart bridge refurbishment".
31. (23 September 2024). "Hobart's Tasman Bridge pathway widening plan scrapped, despite advocates saying existing lanes 'too narrow, too exposed, too badly designed'". ABC News.