BHP Billiton is in the final stages of the approval process for the $30 billion expansion of its existing underground operation at Olympic Dam to create a new open pit mine that would be the worlds biggest – trucks will haul overburden 24/7 for five to six years just to reach the ore body. The combined operations would mine 72 Mt ore per year and would produce 750,000 tonnes refined copper, 19,000 tonnes uranium oxide, 800,000 gold ounces and 2.9 Moz of silver per year.