Higher costs and profits than previously forecast are on tap for the proposed Rosemont Mine, says a new feasibility study.

Building the mine will cost $1.226 billion, or 32 percent more than predicted in an earlier feasibility study done in 2009, says the new report, written by M3 Engineering and Technology Corp. of Tucson. The study was done for Augusta Resource Corp., the Vancouver, B.C.-based parent of Rosemont Copper, which is based in Tucson.

The new study looks at the financial impacts of a recently announced change in Rosemont’s mining plans:

• Augusta has said it plans to produce about 25 percent more copper overall than previously announced because it has found more copper sulfide reserves underground than previously estimated.

• At the same time, Augusta is scrapping plans for a heap-leaching, solvent extraction operation that would produce copper cathodes — almost pure copper bars — from copper oxides, which would have produced 155 million pounds of copper over the mine’s life.

The result of these and other changes is that the company’s projected after-tax income — $6.9 billion over the mine’s 21-year life — was pegged at 43 percent higher in the new study.

Investors in the mine project will get a 37.9 percent return after taxes based on the new study, compared to a 28.5 percent return in the 2009 study.

Read more of this story Sunday, exclusively in the print edition of the Arizona Daily Star.