I had a phone interview first, then was invited for an on-site interview at the mill. That interview was surprisingly casual for a 2 on 1 interview; they asked a mix of experience and technical questions while also giving a general overview of the business and some of the unique challenges it presents. After the interview I was taken to lunch with a couple different people, and again had a very casual discussion. Finally, I was given a tour of the mill itself.
Overall, great interview, professionally done without being overly stressful.