It was the shire's biggest-ever contract involving its Mount Shadwell quarry and could have put a large cash injection into council coffers.

However, the contract price did not allow for more expensive ingredients requested later by the project managers or extra quarrying costs for larger-than-anticipated volumes for the construction site.

Mayor Cr James Purcell said the station deal yielded "hundreds of thousands of dollars" in profit, but could have made more.

"We made money, but not near as much as we could have if we had taken a more commercial approach," he said.

"In total it was worth about $2m and went on for months supplying material for all of the roads and surrounds at the power station.

"They wanted the recipe changed and we had to put more limestone into it."

Cr Purcell said the result prompted a review of the way the shire handled contracts to achieve better results in the future.

"I think we can do the work well enough, but we have to be more aware of our marketing position," he said.

"This triggered us to look at our processes and develop better results for our contracts."

Origin Energy said it was satisfied with the quality of the shire's quarry material and debunked local rumours that the unusually wet winter had caused problems in getting a firm foundation.

The company expects to start producing electricity from its $640m peak-load gas-fired station on Connewarren Lane Mortlake by the first quarter of next year.

Construction started in March last year and at the peak of construction activity there were 380 workers on site.

"Reductions in the workforce will occur progressively during the coming months in line with the project schedule," a company spokeswoman said.

"The power station will employ six to eight people on an ongoing basis when operational.

"Constructio n of the station foundations was completed to design specifications and the turbines and generators have been aligned successfully within a tolerance of two microns."

The station is linked to the Otway Basin gas fields via a new pipeline from Port Campbell.

Two other gas-fired power stations have been proposed to follow Mortlake.

Santos has planning approval for a site near Orford while AGL Energy has earmarked Tarrone for its proposed station.