I had to do the first 6 rows for the local NHL team as the rink got flooded. The stands had to be clean enough to eat off of, so no black tar in anti slip part, and underneath couldn't have any dirt or mud. The e coli count they were looking for was 1 in a billion, you have more e coli on paper money you have in your wallet then that.
We were limited in chems by the consulting company, so we ended up using a straight degreaser, a little brushing and 200 degree water and the stands came out awesome. When I showed up they took between 6-7 hours to do one stand with 10 people involved. Once I showed them how to do things right we cut it down to 1 person a stand for 2 hours max with better results. Remember these were flooded, so mud was every where and took sometime to remove.