, Northern Outcrop - Central (Penwyllt to Penderyn)
map using leaflet map:
The entrance is in the quarry floor and is capped & gated.
A small cave connected to OFD via sump. The entrance passage leads to a what was a short sump, Helen's Horror, but has been a crawl since modification in 2010. Beyond is a junction with a small stream: upstream, Ping Pong Passage leads to a choke, downstream, via a 13 metre pitch, to a Default Chamber with water entering from a perched sump and following narrow streamway to a sump.
First discovered in 1938. Rediscovered and extended by SWCC in 1990.
Sump feeds first inlet in Cwm Dwr Jama
SSSI: 0099 Ogof Ffynnon Ddu (Mixed)
SWCC Newsletter 109
Descent 100, pp.38-40, Malcolm Herbert & Helen Langford, Cwm Dwr II: Its rediscovery and exploration