Mitch,
Welcome and more importantly. congrats on your recovery and for your ability to realize that you are a person who is an addict and that you can escape the hell addiction by seeking new ways to cope and ultimately learn how to live life in a much healthier and happier way.
It is a difficult journey to uncover all the pain and fears that lead one to seeking ways to escape and use, but believe me, it is so worth it to face the fears and conquer them.
I am happy that your employer is open minded and williing to rehire you and even happier to see that it is in a position that lacks easy drug access,and will give you the better chance for succeeding in recovery.