Negotiations over the 36-month contract have been lengthy and at times fractious, with members voting to reject a previous offer and strike on March 9.
A 200,000-strong Brazilian claimant group failed to resurrect a 5.0 billion pound ($6.9 billion) English lawsuit against the mining giant over the Fundão dam failure.
Three drill rigs are operating under the protection of Colombian police and the military following an operation that apprehended several people extracting gold illegally at the site.