Gold mining at South Deep, the world's second-biggest deposit, would never be easy. Located an hour's drive west of Johannesburg, the resource holds 63 million ounces that formed in an ancient lake, now crystallized in rock, three kilometers (1.9 miles) underground. Gold Fields Ltd. has spent 29 billion rand ($2.5 billion) on the mine and has repeatedly missed ramp-up targets due to fatal accidents, mistakes and changing mining methods. A complex geological formation, seismic activity as well as the difficulty of operating high-powered diggers in deep tunnels has slowed progress. Now, armed with a new mining plan and costs under control, it says South Deep will operate at full capacity within five years, and will churn out the precious metal for at least the next 70 years.