That is just the cost for the plant - Holcim is estimating the total development which includes the plant, associated quarries and pits, a new ship to distribute the cement and related national distribution systems at between $400 million and $500 million.
But, despite the new estimates, the Weston plant still remains its preferred option to meet a growing demand for cement in New Zealand.
What could knock it out of contention is the Government's proposed carbon emissions trading scheme.
Its second option is redeveloping its existing Westport plant at Cape Foulwind, which would close if Holcim decided in the first quarter of next year, at the earliest, to build the new Weston plant.
Updated costs for the Westport option are still being finalised and are expected in about a month.
"We expect they will increase by the same order of magnitude," Holcim's capital projects manager, Ken Cowie, said yesterday.
"Those revised costings don't affect our ranking of a new Weston plant as our preferred option."
Mr Cowie said that since 2005 more planning had been done and the estimate was more accurate.
However, what could affect a final decision by Holcim to build the Weston plant could be the Government's Emissions Trading and Renewable Preference Bill, which would establish a carbon emissions trading regime.
It told the finance and expenditure select committee, which is considering the Bill, that Holcim (New Zealand) would not recommend to its parent company that the Weston plant be built if the legislation was passed in its present form.
Holcim's managing director, Jeremy Smith, said that while the company strongly endorsed the Government's decision to establish the trading scheme to help New Zealand reduce its greenhouse gases, it did not encourage Holcim to invest in low emissions technology.
In recent weeks, several amendments to the Bill had been proposed and Holcim continued to discuss the scheme with the Government.
Holcim has received resource consents approval from the Waitaki District and Otago Regional Councils for the new plant, a sand pit at Windsor, limestone quarry at Weston and open cast coal mine at Ngapara, but this has been appealed to the Environment Court.
Environment Court Judge Jon Jackson held a pre-hearing conference on April 28 in Oamaru and indicated a hearing date for the appeals would be dependent on the designation being resolved of the railway line between Waiareka and the Weston plant - a vital component of Holcim's plans.
Holcim's preference is to use the railway line, closed in 1999, to transport materials for construction of the plant and then cement to Timaru's port.
An independent commissioner, Allan Cubitt, appointed by the Waitaki District Council, will consider that designation request from OnTrack at a two-day hearing starting today.
Mr Cowie said that depending on the time frame around the designation, hearing of the appeals could still be held in the last quarter of this year.
