A $35.5 million upgrade to Edgar Dam in Tasmania’s southwest has been completed four months ahead of schedule.
It will strengthen the structure against earthquake risk from the nearby Lake Edgar Fault.
The dam is a critical part of Hydro Tasmania’s Pedder Gordon power scheme, which provides 13% of the state’s electricity needs.
Energy and Renewables Minister Nick Duigan visited the remote site today to mark the milestone.
“The $35.5 million upgrade is about further strengthening Edgar Dam, making sure our critical electricity infrastructure remains safe and reliable for decades to come,” Duigan said.
The project was more than a decade in the making, spanning investigations, design, approvals and construction.
It involved removing the concrete face on the downstream side of the dam and replacing it with layers of filter material, rock, gravel and sand to form a reinforcing buttress.
A new crest wall was also built and sealing works carried out on the upstream side.
Some 60,000 tonnes of material were delivered across 2,000 truck trips, with specific sand sourced from a quarry in northeast Tasmania.
Hydro Tasmania CEO Rachel Watson said the work was driven by an evolving understanding of seismic risk since the dam was built in 1972.
“We realised we had a one in 10,000 risk of there being a major shake around here and we wanted to strengthen the dam to make that a one in a million occurrence,” she said.
The dam’s location near the active Lake Edgar Fault has long raised concerns about the low-probability but high-consequence risk of a major earthquake causing downstream flooding in the Huon Valley.
Duigan pushed back against theories of the dam posing a flood threat to Huonville, saying the modelling should not be “used for nefarious purposes” and that Hydro had a responsibility to make communities safe.
The work was carried out inside the Tasmanian Wilderness World Heritage Area, requiring strict environmental controls including vehicle washdowns, limits on working hours and biosecurity measures.
Hall Earthmoving director Chris Hall said up to 50 workers were on site daily at peak construction, with around 28 living at an on-site camp.
Executive General Manager of Assets and Infrastructure Jesse Clarke said no further major works are planned and the reinforcement should keep the dam reliable for the next 50 years or more.
Further seismic work is planned for nearby Scotts Peak Dam over the next couple of years.
