Senior Structural Engineer Steve Mettam sent us some photographs taken of the bastion tower ruins during their pre-demolition surveys in early 2014.
The subterranean ‘low chamber’ is not currently accessible, except via use of harness and winch, by experienced confined spaces trained personnel only. The castle ruins cannot be seen from the new raised ‘lockable’ double triangular surface cover. The square chamber approximately 4m x 4m x 4m deep is experiencing some groundwater infiltration. We pumped it out once and used infrared heaters to dry it out, but since the demolition finished at the end of February, it has filled up again now to a depth of 0.5m.
We are trying to determine where the water is coming into the chamber, there is a redundant 300mm dia. service pipe running through it, which we have now CCTV surveyed. I suspect the construction joint between the floor slab and the chamber walls has no waterbar incorporated within it, but the water could also be entering via the surround to the pipe or castle ruins. A survey crew is going to enter the chamber shortly, once we have de-watered it again, to record the chamber’s condition and to try to identify where the groundwater is entering it and we shall make an attempt to ‘stem’ this flow.