Australian engineering firm Monadelphous Group Ltd. (MND.AU) said Wednesday that it has secured construction contracts worth a combined A$150 million from BHP Billiton Ltd. (BHP) and Rio Tinto PLC (RIO) for work in Western Australia's Pilbara region.

The contract from BHP is for structural, mechanical and piping installation associated with the construction of an onshore gas plant for the Macedon project near Onslow. The work is scheduled to be completed in the first quarter of 2013, Monadelphous said in a statement.

Monadelphous said it will design and build a gas-transmission pipeline and associated facilities to supply gas from the Goldfields gas pipeline to a new power station at West Angelas for Rio Tinto's iron ore expansion projects. That contract is scheduled to be completed in the fourth quarter of 2013, it said.

-By Robb M. Stewart, Dow Jones Newswires; +61 3 9292 2094; robb.stewart@dowjones.com