I've obtained all the relevant documentation from Costain now, and I am meeting them later in the week to discuss. The output from this process should be an agreed protocol for handling and publicising temporary cave access closures and along pedestrian approach routes to caves as major road works enter the karst area.
Costain's road works are now just touching the upper boundary of the limestone in the Clydach Gorge near to Ogof Nant Rhin for explosives tests. Much later on the substantive road works will reach into the lower Ogof Capel area. So now is the moment that all this starts to affect the caves and caving.
My point is that nobody should have an opportunity to get into or exit a cave onto the surface nearby during any engineering operation that poses a potential risk for the duration of that risk, or to be underground and experience what might seem like an earthquake, or be at risk from rockfall due to thin roof of uncertain qualities, with heavy machinery moving on top or vibrations within the ground. Vibration propagation is partly what the coming week's test will quantify.
This implies closing off a cave at the latest on the day before any test or production blasting begins, having already given as much public notice as possible through all appropriate channels.
One can appreciate that there are many matters for engineers to consider, and stakeholders such as NRW who need to be satisfied, so the clearance from all concerned to go ahead in a particular way on a particular date might all come together quite close to the intended event, thus limiting the notice period available whilst not excusing establishment of safety systems with sufficient reach.
Stuart France
Cambrian Caving Council