One thing I don't understand (well, many, actually): why does the hole have a "one shower a week"? Is this strictly for torture? Not showering seems like a way to degrade and humiliate a person. I (sort of) understand isolating very violent prisoners from the rest of the inmates, but why is torture necessary?
I suppose it's a manpower issue. I guess showers would only happen during the daytime, and outside of meal-times and supervised yard-time. I suppose they could get 3 prisoners per hour through the shower, and probably 40 hours per week shuffling them back and forth to showers. So a pair of guards would be fully occupied doing nothing but supervising showers for 120 inmates in solitary. These numbers my be wildly off, but not an order of magnitude off, and the manpower issue still stands.
Probably a combination of torture and it must be hard work for the prison guards to escort each individual to the showers. So torture and laziness that they can get away with.