Dam fine work provides outcome in Tasmania

07/07/2022

In Tasmania, teams have been hard at work in challenging conditions to shore up one of Hydro Tasmania’s super important pieces of kit.

With long-term predictions of above average rainfall, Hydro Tasmania (a state-owned renewable energy generator) wanted to raise the crest wall of the Murchison Dam, so the dam was better able to withstand large rainfall events.

A team from VEC Civil Engineering (a Downer Company) worked in rugged conditions on Tasmania’s West Coast to raise the existing dam wall by three metres; raise the access road nearby to match the new dam crest level; and install downstream erosion protection.

As you can imagine, working in a remote location like the site of the Murchison Dam, which is about 50 kilometres north of Queenstown, had its challenges.

The dam itself rises 95 metres above the valley floor, is more than 200 metres long and is wedged into the chasm of Murchison Gorge.

There’s no mobile phone communication in the area, so establishing effective communication on the site, and between the site and Hydro Tasmania was essential to manage risk, in particular for safe evacuation in the event of a dam spill – that’s when there’s so much water in the lake behind the dam that it literally spills over the top.

The work involved complex lifting using a tower crane, in a narrow space, at height around a working dam site.

And while the project was construction only, some re-design was needed because there was no commercially available crane that could handle and fit pre-cast panels units that weighed more than 14 tonnes. While re-designing the panel units was pretty straightforward, modifying VEC’s bridge-building excavator was not so simple!

One thousand cubic metres of concrete, 270 tonnes of steel reinforcement and around 15 thousand hours on site were needed to complete the project.

The result is a legacy for Tasmania, keeping communities safe.

The finished works