"B & B Boys: Fred P., Tom N., Al, Tom G. [Tom Gill]
They are at the tunnel entrance at Tennessee Pass, most likely on the east side, not far from the depot location. This is the tunnel that collapsed under the highway in July 2012. They are using movable scaffolding (on train wheels) pulled by a horse along the track in the tunnel in order to perform tunnel maintenance. [Information courtesy of Jimmy Blouch]
