Codelco said it will invest US$4.88 billion over 74 months to convert its open-cast Chuquicamata mine in Chile into an underground operation, Reuters reported Aug. 8.

The investment is a scaled-down version of its original plans, driven by fluctuating copper prices and higher operating costs. When combined with previous spending, the announced investment increases its total costs of converting Chuquicamata to an underground operation to US$5.55 billion, according to the report. It is expected to extend the mine's life by another 50 years.

The Chuquicamata plan is part of a 10-year, US$39 billion overhaul of the Chilean state-owned copper miner's operations to maintain production at its aging mines. The Chilean government committed to injecting US$1 billion to support the operational revamp.

Reuters added that the previous plan drawn up for the mine in 2012 consisted of four levels for the operations but was reduced to three to save investment and operational costs.

Unionized workers recently downed tools for a day over two employee terminations in July. In December 2016, Codelco struck a 27-month wage deal with six unions at the mine, averting the risk of a possible strike at the time.

Unions are also concerned about what the future of the mine will mean for its workforce of 5,664, according to Reuters.