Japanese trading house Mitsui & Co. confirmed Thursday it has been selected to build a desalination plant for BHP’s (ASX, NYSE:BHP) Spence copper mine in Chile, as part of a $2.5 billion mine expansion approved earlier this year and which will add another 50 years to the operation’s productive life.

Mitsui will build the plant at Mejillones port, about 60 km north of Antofagasta city, through a joint venture with Técnicas de Desalinazación de Aguas (Tedagua), a unit of Spain’s ACS Group with strengths in water-related business, it said.