Better days ahead for Florence after a very dark year

The machine has managed to chew through 241 metres of earth since the it was freed two months ago, after an entire year stuck hard and fast beneath Kosciuszko National Park.

The epic entrapment contributed to an enormous cost blowout, with the pumped hydro project expected to cost $12 billion - six times more than originally forecast.

Officials from the Snow Hydro 2.0 project have told senators the wet, soft ground that caused so many problems is behind Florence - for now.

But with more problematic ground ahead, engineers are hard at work trying to prevent a repeat disaster.

"We're mindful that some of the ground conditions ahead of Florence will be challenging, and we are continuing to closely examine options to de-risk this work," Snowy Hydro CEO Dennis Barnes has told a Senate estimates hearing.

There are years of work ahead, with another 15km of boring to go to complete the headrace tunnel.

"We know towards the end of the tunnel, there's in the order of 500 metres to 900 metres of fault zones. We know that will prove challenging."

Mr Barnes says Florence needs to move about 15 metres a day, on average, over the next few years to get the job done.

A range of options are under consideration to speed things along, including procuring another boring machine.

"Over the next one to two months we'll continue the analysis on that and make a decision," he said, adding that it shouldn't require any more money.

Mr Barnes also promised to rehabilitate a large sinkhole that developed in the national park as the machine moved through.

He said Snowy Hydro had recently entered into an enforceable undertaking with the NSW government, including a $300,000 payment to NSW National Parks.

"The hole will be filled in, revegetated. You'll never know it's there."

Australian Associated Press