Hydro Tasmania has recently completed a project to upgrade the Liawenee Canal in Tasmania’s Central Highlands.

The Liawenee Canal was constructed in 1921 and is used to divert water from Lake Augusta to the Great Lake. The water from Great Lake is taken by tunnel through the Great Western Tiers to the 300 MW Poatina Power Station, Tasmania’s second largest hydro power station.

The aim of the upgrade was to increase the capacity of the canal from 18.5 cubic metres per second to 24 cubic metres per second.

This was achieved by widening 1.2 km of the canal and lowering 800 metres of the concrete invert to increase the flow capacity.

Hydro Tasmania project manager Tim Cubit said the success of the project has meant an increase in generation of 28 GWh with a value of around $1.4 million each year.

“This project has increased the capacity of the canal by around 30 per cent, which is significant in terms of the return to our business and the increased renewable energy generation with relatively low impact,” Mr Cubit said.

“Since the project was completed in May 2007, Hydro Tasmania has already gained an additional 13 GWh which could pre-empt a greater average return than first expected when we started the project.”

During the project several challenges presented themselves that required some creative solutions.

“Originally it was planned to use 45 and 33-tonne excavators with rock breakers to excavate the rock, but this process proved too slow and would result in delays in an already tight schedule,” Mr Cubit said.

“The solution was to drill one metre holes within the rock and blast using PowerGel, which significantly reduced the excavation time.

“Laying the concrete in inclement weather posed a further problem, especially when the temperatures in the Central Highlands averaged a maximum of 12 degrees and best practice for laying concrete is above 10 degrees.

“So we created two separate concrete mix designs to be used according to the prevailing weather pattern. These mixes were managed on site through temperature monitoring and the decision on which mix was required was made before the start of each day.”

A significant aspect was the stakeholder management and the effort that was made to manage stakeholder needs and concerns through ongoing communications with all stakeholders affected by the project. These included Hydro Tasmania’s production group which requires regular information about available generation resources and Tasmania’s Inland Fisheries Service, which uses the canal for spawning trout.

“It was critical that the project be completed on time to meet generation requirements for the winter period, which is Tasmania’s peak energy demand period and coincides with the spawning of brown trout between May and July,” Mr Cubit said.

“Tasmania Police and the Tasmanian Parks and Wildlife Service also use the canal for their water supplies and we arranged for water to be supplied during the outage period.”

Due to the location of the canal and it close proximity to the Central Plateau Conservation area, the project team was required to put in place stringent environmental management protocols.

The surrounding area is home to three endangered species - the Spotted Tailed Quail, the Brown Poa Butterfly and the Tasmanian Devil. A carefully prepared environmental management plan was developed and implemented to ensure the project did not impact on the surrounding environment.

Being built in the 1920s, the heritage values of the canal also required consideration and a Heritage Impact Assessment was undertaken and used during the project.

Overall the project achieved the objective of substantially increasing water flow through the canal into Great Lake, creating a more sustainable storage at a time when the lake was at an historic low level due to the ongoing drought conditions in Tasmania’s Central Highlands.

The project was completed on time and under budget. The contractor for the project was Hazel Bros.