VANCOUVER -- BC Hydro will pay a consortium of three companies about $1.75 billion to build the largest components of the controversial Site C hydroelectric dam.

The Crown corporation announced last month that Peace Hydro Partners was the preferred proponent to build the earthen dam, foundation, two diversion tunnels and spillways in the province's northeast.

It initially estimated the work would cost about $1.5 billion, but announced on Monday it would pay the boosted fee to ACCIONA Infrastructure Canada Inc., Petrowest Corporation and Samsung C&T Canada Ltd.

B.C.'s Opposition New Democrats are criticizing the deal, saying there is no guarantee that British Columbians will get the work.

The BC Building Trades Council also says it is shocked, claiming as many as 1,500 jobs may go to workers from Alberta and Saskatchewan.

Legal challenges against the dam have been launched by several groups and First Nations over concerns about flooding and the impact a new lake will have on the Peace River area.