Robot miners are gearing up to descend one mile to the bottom of the Bismarck Sea near Papa New Guinea. Their mission? To collect deposits of gold, silver, and copper.

The robots are being built by Soil Machine Dynamics, a manufacturer of subsea robotic vehicles, for Toronto-based company Nautilus Minerals, IEEE Spectrum first reported. The robots are being tested in 2016 and, if all goes according to plan, they will depart in 2018 for 30 months.

The massive, subsea robots will be deployed via a nearly 750-foot vessel built in a Chinese shipyard. For their first real foray out to sea, the robots are expected to bring up 2.5 million metric tons of ore containing metal that could cost more than $1.5 million.

Three robots will be sent to collect the ore — all with different jobs. One chews through the metal-rich chimneys that form as a result of super hot water coming out of sulfurous vents in the seafloor. The second robot then comes in and uses its strength to pulverize rock walls.

The third then feeds the crushed rock up a pipe that is dangling from the vessel the robots were sent out on.

Nautilus is attempting to calm any environmental concerns by creating a refuge zone in the leased the land the robots are mining. That refuge zone is intended to provide a source for local fauna to recolonize.