I am going through the hire in/waiting on a start date process as well.
I'm also at a TVA construction project, so I know that pushing or getting anxious doesn't make things happen.
I know that in my case, there have been times when they've been hard to get in touch with, you've just got to continue to call.
I also know that the HR person that I'm dealing with is working as hard as she can to get the group in.
Just keep calling, understand that they're dealing with more than just you, and they're doing all they can.
To the guy who just attempted career suicide, hope you learned a lesson while staying anonymous.