When we left our heroes, they had dropped the main electrical panel into the basement, prewired with all the connections for module "B". Now they're feeding all the connections for module "D" down through "B" to the basement.
But there's a catch. The conduit through module "B" is obstructed halfway through. So here the SetWright foreman is trying to clear the obstruction, while the crane suspends the 10 tons of module "D" above him. No luck, so he cut a separate passage, and we'll route it properly later.
That conduit existed only to make his life easier.