Sonia,
My ex worked with his OW, too. They worked in the same department, but not like elbow to elbow with eachother. The thing is - you probably won't feel "comfortable" as long as they come into contact with eachother, no matter how infrequent. Your H probably doesn't understand that and he may never! He doesn't know the anxiety you have about them running into eachother. The area we live in, my ex had a FANTASTIC job and that was his excuse to stay. The real reason was probably something closer to him not wanting to NOT see her. I begged him to quit and he refused. So, every night he went to work, I got the same sick feeling as I did the night I found out. I didn't sleep (he worked 3rds, too). I was a WRECK. Add to that, that the OW's H took a job there to spy on them and called on every break (2 a.m. and 4 a.m.) with a report of all of their activity. Even if I slept, accidentally

it wasn't for long!
After his OW divorced her H, the very day actually, she told her H that she was "free to chase" my ex and that they'd begun talking again. I told him to get his stuff and be gone by the time I got home from work. He finally realized that I had drawn my very last line in the sand and never went back to the job. He called a friend in construction and started the next day, with him. He took a BIG pay cut, but you know what, I'd rather live on Ramen Noodles than be miserable about him working with HER.
In the meantime, dear Sonia... keep looking out for YOU. Keep journaling, scrapping, exercising, hanging out with the kids. Do anything you can think of to keep your mind off of it.
The thing is, your H has to realize that he's going to have to make some sacrifices for YOU and the marriage. It's not about him or what makes him comfortable. Change is scary for most people, but sometimes, it is absolutely necessary to bite the bullet and JUST DO IT. This is one of those times. He can tell you all the live long day that he's done with her and doesn't talk to her - and that may be true - but nothing but a transfer or new job is going to give YOU the security you need. Your H was in a new situation when he started that job - he's really going to have to think about taking one for the team and looking for something new. Or, at least get the ball rolling.
I'm so glad you came back, Sonia.
Monica
"I have all I've waited for and I could not ask for more"