mudman said:
You could park at Blackrock and go through the underpass (if it's still open) and walk down from there. However, I don't think there is official pedestrian access at the moment.
The underpass near where the Old Drum and Monkey Inn was situated is supposed to have been converted to a bat flyway using concrete rings. I haven't seen anything in the road-widening plans which explain how pedestrians will be able to cross the road here for passing from the northern to the southern side of the gorge via the Devil's Bridge. This is very important for access to Ogof Capel, Shakespeare's Cave and the Pwll y Cwm riverbed pothole, which provides diving access to Daren Cilau, having been dug open and first passed by a diver from the cave system inside the mountain to the gorge.
Ogof Nant Rhin is some distance upstream and the real access point was the lay-by 2/3 of the way up the Clydach Gorge, heading towards Brynmawr. A climb over the fence and descent to the river would have taken you straight to the cave entrance, almost directly below the bottom end of the parking area.
I've provided to Phil Baker of Costains, via John Hill of Brynmawr (22/5/15 12:13) and, previously, a locally based caver (10/3/14 18:30), extracts from my guidebook to the caves of the Clydach Gorge, describing the location of and access to the various cave entrances in the Clydach Gorge, in order that these can be preserved during and after the roadworks, but I have yet to hear anything back in return.