Portland's aluminium smelter faces "substantial challenges" to ensure its safe and ongoing operations after a storm tore down high-voltage powerlines near Cressy and left the business without power for about three hours on Friday.
The extent of the damage to the 500kV powerline towers means repair works could take some time.
It is the second externally-caused outage to significantly impact the smelter in less than three months following a similar outage in November.
Alcoa of Australia president Michael Gollschewki said it would take some time to assess the operational impact of the significant event, and the focus at this time was on the safety of the plant and its workforce.
Mr Gollschewski said there was also a major focus on getting the second transmission line operational, without which the smelter was at significant danger of further unreliable supplies and operational impacts.
"We have substantial challenges ahead of us to ensure the safe and ongoing operations of the Portland Aluminium Smelter," he said.
Power to the smelter's two potlines was lost about 2.30pm after a storm cell tore six 500kV towers from the ground.
District Six operations officer fire Mark Gunning said an eyewitness reported the sky turning black and square hay bales flying down the road.
Partial power - about 50% per cent capacity - was restored to the smelter's two aluminium potlines about 5.40pm.
It took about another four-and-a-half hours for power to be substantially restored.
The smelter was receiving power from only one of its two incoming 500kV transmission lines, leaving it exposed should there be further supply issues.
Mr Gollschewski said its focus was on ensuring a safe work environment.
"We are extremely grateful to our workforce for their ongoing dedication to the plant," he said.
"We recognise the importance of the smelter to our employees, their families and the community.
"We appreciate the support of government and community leaders who we continue to work with constructively."
Power company Ausnet services said six towers were blown over and two others were extensively damaged, but work to repair them could be lengthy.
"We have crews at the site making the area safe and assessing the extent of the damage," a company spokeswoman said on Friday.
"We will work to repair and reconstruct these lines as soon as possible, given the extent of the damage it will take some time."
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