This large wheel case or wheel pit stands next to the stream which flows from the north into the head of Cwm Orthin, and on which there were formerly several sizeable reservoirs from which water was piped through siphons to Level 9 mill (NPRN 408866) and the reservoir in Level 4 adit (NPRN 408860). Neatly constructed of huge blocks of slate, it could have housed a waterwheel 40ft diameter by 6ft wide (12.2 x 1.8 metres), but it seems that a wheel was never put in place. A waterwheel in this position might have been intended to drive a cable hauling trucks along the waste tip (NPRN 408869), with a winding drum in the adjacent pit. The water supply would have come from the rectangular tunnel at the side of the high platform a few metres to the west, which would have brought the tailrace water from the wheel which powered the Level 9 mill.
W J Crompton, RCAHMW, 23 July 2009.