During the Great Depression when people were lucky to find a job, a job for these tunnel workers proved fatal. In the 1930's,  764 of the 1,213 men who worked at Hawk’s Nest tunnel near Gauley Bridge, West Virginia, for 2 months or more, died within 5 years of the tunnel’s completion. They died because they were drilling through the rock which was silica and they contracted silicosis...

The hydroelectric power tunnel was owned by Union Carbide (the US chemical concern best known for the Bhopal disaster in India. Now owned by Dow Chemical Company). The tunnel construction was all gain for Union Carbide. Not only a tunnel was built, but also the excavated silica was used in the concern's steel mills.

https://face2faceafrica.com/article/remembering-the-avoidable-tunnel-disaster-in-the-u-s-that-killed-hundreds-of-black-workers