Codelco has received an environmental permit for a $1 billion expansion of its Salvador mine, the state-controlled copper company said on Friday.

The Rajo Inca project will increase production at Salvador to 90,000 metric tonnes per year of copper, up around 30% from current levels.

Reserves at the underground operation at Salvador are due to run out next year.

Changing the extraction method to open pit mining is therefore urgent as it is the only way to continue operations to extract available resources, Codelco said in a statement.

“We are very satisfied with the speed with which Rajo Inca has advanced. We began prefeasibility studies in 2015 and expect to enter operations in 2021,” said Codelco CEO Octavio Araneda.

Rajo Inca is one of the six major investment projects Codelco is advancing to bolster production at its aging mines.

A new underground operation at the company’s Chuquicamata division entered production last year while a new mine level at the underground El Teniente mine will follow in 2023.