The digging crew are using a skid steer for some reason. Since the idea is to be secretive this makes no sense as:
1. There would be no way to vent the carbon monoxide fumes out of the digging area without using noisy fans 2. They don't use a spotter to prevent the type of accident that occurred from happening. Experienced sandhogs (tunnelers) would know this. 3. The initial digging seems to have been over with, meaning that there was nothing to the skid steer to do in the hole.
1. There would be no way to vent the carbon monoxide fumes out of the digging area without using noisy fans 2. They don't use a spotter to prevent the type of accident that occurred from happening. Experienced sandhogs (tunnelers) would know this. 3. The initial digging seems to have been over with, meaning that there was nothing to the skid steer to do in the hole.
There are no welding curtains around the welding work being done in the dig. This is a rookie mistake as it would cause the men to get welder's burns (eye flashes) and cause injuries.
It actually too dark in the dig project to do any actual digging. OR shoring up, setting forms or even reading blueprints and diagrams.