Currently the mill is closed. However, the grounds are still open and you can photograph the mill from the outside. In fact, the state officials there were very helpful and obliging with my photography yesterday.
The reason it is closed is that there were a couple of dams around that had been built without fish ladders, etc. These dams had been primarily built to provide water for the mill which doesn’t operate anymore. So with the combination of the damage to fish populations and the dams are now obsolete, they were removed. This lowered water levels in the mill trace and the extinguisher draws its water from there. So, currently it doesn’t meet fire safety standards. This is only temporary; the mill will reopen.