Local media report the state-owned company will accept applications from today from people interested in working on the project.
The miner describes Chuquicamata as the largest openpit mine in the world. The underground expansion, which was originally approved in 2015, is expected to extend its life by at least 40 years.
Codelco generated $1.6 billion in the third quarter, exceeding its target of $254 million more than six-fold.
Its direct cost was 131.8 cents per pound which it said was 9% lower than the industry average.
CEO Nelson Pizarro said at the time that lessons learnt in 2015-16 had instilled cost austerity and productivity "in our DNA" which allowed the company to be competitive beyond the vagaries of the copper price.