Duratec recently restored Darlington Jetty at Maria Island in Tasmania – gateway to extraordinary landscapes and fascinating histories.
Natural beauty meets rich heritage
Located in the Tasman Sea, four kilometres off the east coast of Tasmania, Maria Island is home to the Tyrredeme people, the Traditional Owners of the land. In 1972, the island was recognised for its fauna, flora and geological values and declared a national park. It is also listed on the National Heritage List, Register of the National Estate and Tasmanian Heritage Register. In fact, the island’s Darlington Probation Station is part of the Australian Convict Sites which became a World Heritage-listed place in 2010.
This historical significance, combined with its cultural importance and natural beauty makes Maria Island a popular tourist destination. Visitors travel to the island by ferry, departing from Triabunna on the mainland and disembarking at Darlington Jetty, the island’s primary access point.
Many storms weathered
The jetty’s location at the exposed, northern tip of the island means it is subject to strong westerly winds, as well as high-energy wave action and swell surges from the north-east. Such weather conditions impact the jetty’s structural integrity and by early 2024, Tasmania’s Department of Natural Resources and Environment recognised the need for repairs.
The jetty had last undergone works in 2014 when the old timber structure was replaced with new reinforced-concrete wave panels. While reactive repairs to storm damage and deterioration had been carried out since then, more comprehensive remediation work was now required to significantly extend the jetty’s service life.
About the jetty
Darlington Jetty is an L-shaped structure, which includes a lower landing platform, and is protected by a breakwater at the head. Its concrete deck is supported by steel piles attached to concrete crossheads in some areas, while other sections feature timber piles. Reinforced-concrete wave panels are designed to break down wave energy and provide protection to moored vessels.
The works required
After investigating the extent of the deterioration, the Department of Natural Resources and Environment divided the works required into three packs consisting of the following tasks:
Work pack 1: Wave panel upgrades and deck repairs
Wave panel upgrades
- Removal of wave panels
- Fabrication and installation of new steel walers to support wave panels
- Reinstatement of wave panels
- Supply and installation of fastenings to wave panels
Deck repairs
- Lifting of deck panels (while wave panels are removed)
- Replacement of bearing pads under deck
- Refastening of deck panels with through-bolts to crossheads
Work pack 2: Pile repairs
- Repairs to selected piles using concrete repair system
- Wrapping of remaining piles with FRP protection system
- Removal of raker piles and installation of steel bracing
Work pack 3: Miscellaneous
- Supply and installation of new fenders
- Supply and installation of new access gate
- Fabrication and installation of new safety barriers
- Coating of safety barriers
- Supply and installation of fasteners to headstocks
- Removal, coating and reinstallation of steel ladders and bollards
Not your average job
There are many aspects of this project that make it stand out from others, not the least of which is its location – stunning scenery, steeped in history. As with all jobs, however, there are always challenges to keep project teams on their toes.
Over the years, Duratec has honed its ability to take an agile approach to projects. Should an issue arise – as it inevitably does – team members take pride in working together to come up with creative solutions.
It’s this sense of project ownership and accountability (a Duratec value) that sets the company apart from the rest; a determination to get things done, perhaps in a way they have not been done before.
Maintaining a ‘live’ jetty
Throughout the works, Darlington Jetty was to remain fully operational, which meant accommodating the Maria Island ferry service. The Duratec team became well acquainted with the timetable, which saw the ferry dock four times a day.
As much as possible, works were scheduled outside of the ferry’s operational hours of 9am to 4pm. When this was unavoidable, however, Duratec’s commitment to establishing clear lines of communication meant the ferry operator was notified well in advance.
Navigating tides
Access to the worksite was greatly affected by tide levels and ocean swells. While Duratec had taken this into account from the outset and analysed tidal charts, the team adopted a flexible approach to access methods and methodologies, largely due to frequently changing conditions. Various marine vessels and temporary access systems allowed team members to choose the method best suited to each situation on a case-by-case basis.
Local people, local knowledge
Further facilitating the navigation of tides and swells was local knowledge of the conditions and familiarity with the jetty itself. Duratec has offices in both Hobart and Launceston, and makes a point of employing people from the areas in which it works. This meant the project team incorporated personnel who were not only used to the tidal conditions but had also worked on the jetty before.
Working on water
To access the jetty, Duratec chose from multiple marine vessels depending on the circumstances, i.e. job location, job duration and tidal conditions. One of the boats had been used for repairs to the jetty in the past, which meant its operator had knowledge of the area and provided a cost-effective solution.
The marine vessels and their uses were as follows:
Ningaloo Spirit: Diving operations and emergency rescue
Ambush: Lifting wave panels and concrete decks
Lego Barge: Lifting steel assets, e.g. walers and rakers
Duratec barge (purpose-built): Pile-wrapping and headstock bolt replacement works
Duratec punt: General transport and emergency rescue
Working under water
Duratec has extensive experience in the marine sector, repairing all kinds of wharf infrastructure, from fenders and dolphins to piles and beams. To complement its own self-performing workforce, the company subcontracts independent operators for specialised tasks. In this case, Duratec engaged trained and qualified divers to carry out underwater repairs, such as the removal of rakers, installation of walers and repairs to piles.
How’s about that weather?
As the saying goes, “you can do much, but you can’t control the weather” and such was the case for the Darlington Jetty works. The program was extended significantly due to weather constraints with works running from June to November 2024.
While wind speed and direction were accounted for at the time of tender, surge conditions caused by ocean swells were more difficult to predict. On a number of occasions, forecasts indicated that winds would fall within workable limits, however, unexpected 5m winter swell events brought about conditions that were not conducive to works in, above or near water.
The expected unexpected
The remediation of Maria Island’s Darlington Jetty was no mean feat. The worksite presented various challenges, many of which were predictable and some that were not. Still, Duratec’s agile approach meant the project team was able to pivot, sometimes at short notice, in order to deliver a successful project outcome.