Bumpy bits straddled by Lyell Highway upgrade

By Rosemary Ann Ogilvie

The long-overdue upgrade to the Lyell Highway, currently being undertaken by Andrew Walter Constructions, fulfils a state government election promise to improve this heavily trafficked route, which runs from Hobart to Queenstown on Tasmanias rugged west coast.

The Lyell Highway Murphys Flats overtaking lanes to Molesworth Road Junction as the project is officially titled is the second section being built by Andrew Walter Constructions. The first stage from Limekiln Point to Murphys Flats and Molesworth Road to New Norfolk, was completed late November 2008. A third stage is yet to go to tender.
The current project, which started at the end of November and is scheduled for completion at the end of June, involves two sites: Part A ($2.5m) and Part B ($1.5m). Running north and south of the notorious section dubbed the bumpy bits, about halfway along the highway to New Norfolk, each site is approximately 2km in length.
Road moves
Much of this highway is built on river flats, explains project manager and civil engineer, Stewart Geeves. Consequently, certain parts of the road settle and move fairly continuously. The bumpy bits section just keeps on moving. Every few years they put more asphalt on, so there are sections that are claimed to have had metres of asphalt applied over the course of 50 years.
The most recent reconstruction was completed a couple of years ago by Roadways, and to date the road has behaved quite well, says Geeves. Its something DIER (Department of Infrastructure, Energy and Resources) has to monitor and maintain as necessary. Theres not much scope to reposition this part of the highway as it runs along the edge of the Derwent River. The banks alongside are fairly steep, so it would involve extensive earthworks, and you would probably encounter some significant rock excavation as well.
The sections now being upgraded however, are mostly on fairly solid ground. The job involves reconstruction along the existing alignment, but with horizontal and vertical curve improvements. The first part requires about 40,000m of excavation, the second 11,000m.
Cut material into hardstands
About one third of this material went into constructing the embankments, says Geeves. The remainder was used either to build hard-stand areas for the Motor Yacht Club of Tasmania, which has a racecourse for power boats, or in constructing level hard-stand areas for local landowners.
With the road being so close to the river, sediment control is a major factor. We used the usual silt-stop fences and basins at the outlets of all the culverts to deal with this. DIER had to make a commitment not to increase the number of culvert outlets into the river. As there are also a number of declared weeds along the alignment, care is required to identify and appropriately dispose of material from these areas.
The fact that this is an extremely busy part of the highway many adults and children in the region commute to Hobart workplaces and schools meant difficulties with traffic flow, especially when the children returned to school in mid-February. It was reasonably manageable up to that point, says Geeves. However, once school started we had quite significant hold-ups in the morning and afternoon peaks. This required a fair bit of extra work, including going back to manual traffic control in order to reduce delays.
While theres an alternative route on the northern side of the river, people tend not to use it because of the lower standard of that road, and it would generally involve a longer trip.
Supportive residents
Despite the delays local residents on the whole have been supportive of the work as theyre pleased to see the upgrade, particularly as it should significantly improve the safety of the road.
The biggest challenge apart from dealing with the traffic is the staging of the work. Some of the levels on the original road and the new road are significantly different, says Geeves. So weve had to stage the construction in order to get the traffic from the old section onto the new one. This is quite tricky, and probably a bit frustrating for drivers as well.
Additional traffic disruption was prevented through the use of precast bases rather than cast-in-situ concrete, in constructing a box culvert across the Highway. This allowed us to get the crossing through within about two days rather than staging it over the course of several weeks, says Geeves. Its a much quicker process, which obviously minimises the inconvenience.
Because the section of the highway between Hobart and New Norfolk is one of Tasmanias earliest roads Denis McCarty, a colourful and entrepreneurial Irish political prisoner turned police constable, built it between 1818 and 1819 heritage issues were significant. Sites in the area with historical and heritage significance include a former mail coach inn site on the southern side of the highway, a National Trust commemorative marker, the Altamont Government lime kilns, quarries, a landing place and a convict settlement.
Georgian homestead
One of the many old houses that line the route, the heritage listed Georgian homestead Scottsdale, had significant restrictions relating to access and tree removal. The historic lime-burning works and limekiln that survive from a distant era when the limestone-rich terrain was quarried and burned to make lime, was fenced off to ensure no one accidentally strayed into them and caused damage.
In common with most other Tasmanian contractors, Andrew Walter Constructions now uses GPS survey systems to do the setting out and to control the levels. Geeves notes that this helps improve productivity, and also reduces direct costs of surveying as the surveyor spends less time on site.
Major contractors for the project include Roadways, which is responsible for sealing, and Zaganite, which is handling the line marking. Humes supplied the pipes and units for the pre-cast box culvert installed across the road. Hazell Bros HBMI Quarry is supplying the aggregate.
Paul Bramich and his crew at Reveg Tasmania are carrying out the landscaping works, including erosion matting and hydroseeding/hydromulching. A relatively new company, Protector Rail, is constructing the guard fence and wire rope safety fence. Theyve done some work for us previously and we very impressed, Geeves said.