Tasman Bridge disaster

The collapse of Tasman Bridge isolated two sides of the city which had heavily relied upon it for most daily activities.[7] 30% of Hobart's residents lived on the eastern shore and were effectively isolated. The day after the incident, as 30,000 residents set out for work, they found that the former three-minute commute over the bridge had turned into a 90-minute trip.[8] Within an hour of the incident, the Sullivans Cove Ferry Company started services across the river, and continued its services throughout the night.

Three private ferries were in place the next day while the Kosciusko, Lady Ferguson and Lady Wakehurst that were loaned by the Public Transport Commission, Sydney.[9][10] People on the eastern shore quickly became isolated, as most schools, hospitals, businesses and government offices were located on the western shore. Prior to the disaster, many services on the eastern shore were severely lacking.[11] Access to medical services in particular posed problems for residents in the east, as services consisted only of local clinics. Hobart's hospitals—the Royal Hobart Hospital and the Calvary Hospital—were located on the western shore. What was previously a short drive across the river became a 50 km (31 mi) trip via the estuary's other bridge in Bridgewater. Most of Hobart's cultural activities, such as theatres, cinemas, the museum and art gallery, restaurants, meeting places, lecture theatres and the botanical gardens, were located on the western shore.[12]

The disaster caused a variety of social and psychological difficulties. Although comparatively minor in loss of life and damage, it presented a problem beyond the capacity of the community to resolve.[8] The disaster had unique characteristics and occurred at a time when the effects of disasters on communities were not well understood. "Opportunities for the community to be involved in the response to the disaster and the physical restoration of infrastructure were minimal because of the nature of the event. It is likely that this lack of community involvement contributed to the enduring nature of the effects of the disaster on a number of individuals."[12]

A study of police data found that in the six months after the disaster, crime rose 41% on the eastern shore, while the rate on the city's western side fell. Car theft rose almost 50% in the isolated community, and neighborhood quarrels and complaints rose 300%.[8] Frustration and anger was directed towards the transport services. Visible progress on restoration of the bridge was slow because of the need for extensive underwater surveys of debris and the time required for design of the rebuilding. "The ferry queues did however provide some assistance by providing a forum where people with much in common could vent their frustration."[12] A sociological study described how the physical isolation led to debonding (the setting aside of bonds that constitute the fabric of normal social life). The loss of the Tasman Bridge in Hobart disconnected two parts of the city and had far-reaching effects on the people separated.[13]

The disaster was a major contributor to ferry services being the lifeline for people needing to cross the river for daily work. Bob Clifford was the major operator of ferries at the time, and quickly built more of his small aluminium craft, using his company Sullivans Cove Ferry Company. He later went on to become the major Tasmanian shipbuilder with a firm which continues today, called Incat.[14]

View from the eastern shore showing the rebuilt pylon #18. Pylon #19 was not rebuilt.

In March 1975, a Joint Tasman Bridge Restoration Commission was appointed to restore the Tasman Bridge. The Federal Government agreed to fund the project, which began in October that year. The reconstruction included modification of the whole bridge to accommodate an extra traffic lane, allowing for a peak period 'tidal flow' system of three lanes for major flow and two for the minor flow. Approximately one year after the bridge collapse, a temporary two lane Bailey bridge 788 m long, linking the eastern and western shores of the Derwent, was opened.[11]

Specialists in marine engineering undertook an extensive investigation to locate bridge debris. This survey took several months to complete, and parts of the bridge weighing up to 500 tons were accurately located using equipment developed by the University of Tasmania and the Public Works Department. Maunsell and Partners were appointed consultants for the rebuilding project. The firm John Holland was awarded the construction contract.[15] Engineers decided not to replace pier 19 as there was too much debris on the site.[16] The Tasman Bridge was re-opened on 8 October 1977, nearly three years after its collapse.[1] 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.[17]

The engineering design of the Tasman Bridge provided impact absorbing fendering to the pile caps of the main navigation span capable of withstanding a glancing collision by a large ship, but all other piers were unprotected. This disaster shares some common features with the Skyway Bridge collapse in Florida in 1980, and the I-40 bridge disaster in Oklahoma in 2002, both involving collisions with ships. When river traffic "comprises large vessels, even at low speed, the consequences of pier failure can be catastrophic". In the field of structural engineering, the concept of ‘pier-redundant’ bridges refers to a bridge superstructure which does not collapse when a single pier is removed.[18] Two ‘pier-redundant’ bridges have been constructed in Australia – over the Murray River at Berri and at Hindmarsh Island in South Australia. The probability of ship impact is now regularly evaluated by specialist consultants when designing major bridges. One solution is to protect bridge piers through strengthening or the construction of impact-resistant barriers.[19]

The disaster resulted in changes to the regulations pertaining to shipping movements on the Derwent River. In 1987, a system of sensors measuring river currents, tidal height, and wind speed was installed near the bridge to provide data for ship movements in the area.[20] The Marine and Safety (Pilotage and Navigation) Regulations (2007) contains specific provisions dealing with the Bridge, e.g.:

"The master of a vessel approaching the Bridge to navigate it through a span must (a) have the vessel fully under control; and (b) navigate the vessel with all possible care at the minimum speed required to pass safely under the bridge".[21]

Vessels above a certain size are required to be piloted, and vehicle movements on the bridge are temporarily halted when large vessels are to pass underneath the bridge. As an added precaution, it is now mandatory for most large vessels to have a tug in attendance as they transit the bridge in the event that assistance with steerage may be required.

2005 panorama of Hobart illustrating the extent of the city's reliance on the Tasman Bridge

The disaster stimulated development in Kingborough, a municipality south of Hobart on the western shore, because of the reduced travel times for western shore workers compared to the eastern shore. The eastern shore eventually became a more self-contained community, with a higher level of employment and improved services and amenities, than had been the case prior to the disaster. The previous imbalance between facilities and employment opportunities was redressed as a result of the disaster.[12]

A new bridge crossing the river, the Bowen Bridge, was completed in 1984, a few kilometres north of the Tasman Bridge.