Ogof Afon Nedd Fechan - May 1987.

Ogof Afon Nedd Fechan, the Little Neath River Cave is situated in the upper Neath valley near Ystradfellte, about 10 miles south-west of Brecon in South Wales. I first visited the system in 1980 and have been back many times, exploring most of the passages accessible to non-divers.

The system was discovered in 1967 by divers who pushed the terminal sump in Bridge Cave, a system known since the thirties. The divers struck lucky ... the system they had entered proved to be over five kilometres in length. During the initial explorations, an upstream passage was followed to a point where cracks of light could be seen and surveying the passage located the point in the bank of the river outside the system. An application of 'Dr Nobel's linctus' and the system was open to non-divers via the newly opened 'Flood Entrance'.

About two kilometres into the system, a further streamway sump was encountered. This, and the following two sumps were pushed by divers and a further 2km or so of passage discovered. This part is, as yet, accessible only to divers and having pushed the upstream passages extensively, the sight of the downstream passages on the survey was frustrating, so much so that when college presented an opportunity to learn to dive, I jumped at it!

The upper Neath valley drains a significant area of hills on the lower edge of the Beacons and Black Mountain and consequently swells after rain. The cave floods frequently and quickly requiring great care to be taken with the weather. The streamway beyond the streamway sumps backs up 20 metres in high flood and under such conditions fills to the roof.

After two attempts were washed out with high water conditions, plans were made to do the trip on Spring Bank Holiday weekend. The two weeks before had been fine but the weather had started to break towards the weekend. John and I drove down to Caerllwyn, the Westminster Spelaeological Group's cottage at Hirwaun on the Friday night laden with gear. We'd doubled up on just about everything including additional larger cylinders from which to decant to the smaller bottles. We planned to dive with a 28 cu ft and a 14 cu ft sidemounted, giving us two independent sets each.

The Saturday looked iffy, with localised thunderstorms forecast. Sunday's forecast was better so once again we had to wait. Rather than waste the day, we went over to Ogof Ffynnon Ddu, a feeder of the river Tawe. This system, the deepest in the UK, contains of over 43 kilometres of passage and provides many sporting trips. Later, we spent time preparing our harnesses and generally getting things ready.

We were up at around 9 am on Sunday and after a fearsome breakfast and another check through the kit, we drove over to the Neath Valley. We paid the usual courtesy visit to the farmer and 20p goodwill fee and set about kitting up. We'd fitted the kit into two tackle bags, each weighing 17 kg and were both wearing 6mm wetsuits, 3 kg of lead and 3 kg or so of headlamp battery to ensure we didn't scrape along the roof of the sumps too much. For diving lights, we had two or three Aquaflashes each, fixed to the side of our helmets.

Bridge Cave was entered at 11:45 and we were soon grunting along the initial crawl to the boulder choke. Much passing carrying and dragging of gear got us to Bridge Cave's impressive main chamber, 100 metres long, 10 metres wide and 10 metres high. with a fair streamway in the floor. The roof lowered and after 45 metres of crawling and grovelling we reached sump 1 Bridge Sump. We had both dived this sump at least three times previously and simply put a regulator onto the 28 cu ft. cylinder and hung the valve out of the tackle bag.

I dived first and followed the emergency telephone cable for 18 metres to surface in Little Neath River Cave 2 (LNRC 2). John surfaced about 30 seconds later and we set off on the 1.5 km carry to sump 2. Fortunately about half the route is along the main streamway and the bags could be carried on our backs. The first 150 metres however are only 80 centimetres high, but over half full of water. The 700 metres leading to Sump 2 is also low and a lot of energy was expended transporting the gear.


An hour and three-quarters after entering the system we arrived at Sump 2. We checked through the gear again and helped each other kit up. When we were both happy, I led off from base, squeezing through the 30 cm gap across small stones for 5 metres or so to the sump. A couple of minutes searching revealed the line and I led off, breathing from the 28 cu ft bottle on my left-hand side. The sump was initially 30 cm high, but eased to a more comfortable 80 cm. Width was about 2 metres and the visibility soon cleared to 2 metres.

Finning gently downstream, my lights penetrating the gloom, I followed the line downstream for 35 metres until the floor rose, reducing the passage height, forcing me to squeeze through to surface in LNRC 3. The 40 metre long dive had taken about a minute, with a maximum depth of -2 metres. John surfaced after a short while and we crawled the 10 metres across the chamber that formed LNRC3, 10 metres high by 6 metres wide, to Sump 3.

Checking the gear, John led off and I watched his lamps disappear. I waited holding the line for about a minute or so before fitting the gag and diving. The water was about 8C but I hardly noticed as I was still hot from the carry. Sump 3 started off wide with plenty of height but soon narrowed to 1.5 metres.

As I progressed, a large pothole could clearly be seen in the floor, some 3 metres deep. I pressed on through comparatively large passage, the line keeping me to the right-hand wall - black limestone with veins of white marbling. A slight lowering of visibility after 55 metres signalled the end of the sump. A few more metres and I surfaced in LNRC 4. a lofty passage with a rocky streamway.

Fins were removed and we hobbled over the boulders in wetsuit socks for 45 metres until once again the roof lowered at Sump 4. I dived first, into comfortably sized passage, a metre high and probably 2 metres wide. Identifying a distinct bend to the right meant I was about halfway through and after about a further minute or so the sump widened and the floor rose. This time it was a bit tighter and I had to move boulders aside until I could squeeze into LNRC 5. John surfaced a short while later and we de-kitted, stacked the gear on a sandbank out of the streamway and set off to look around.

We identified Foot and Mouth passage on the right and the main streamway continuing ahead toward Sump 5. However, two slippery overhanging climbs - using thin diving line to haul on - and a 20 metre flat out squeeze saw us at the junction with Contortionist Passage. A right turn and a climb up through some very loose boulders revealed our goal, New World Passage - a large stream abandoned oxbow.

The sandy floor was strewn with boulders and sloped away to the right. As we progressed, the passage widened to 25m and probably 20m high. There are some fair size chambers in the cave, but this is the largest. We continued for 400 metres or so until the passage narrowed. Both left and right provided ways down to the streamway some 14 metres below. These were left for another day as the climbs were awkward and an accident this far into the system would have been disastrous. There were also climbs down through the boulders at the and of the chamber, heading to Lake Chamber.

We retreated back to Sump 4 and continuing down the main streamway for 400 metres or so reached Sump 5. After a good look at the, by now, rather soggy survey and 2 hours after we'd entered New World, we retraced our steps back to Sump 4, re-kitted and commenced the dive out. Visibility was generally better upstream and we both took our time in Sump 3 watching the trout and dropping into the pothole in the floor.

Arriving back upstream of Sump 2, we re-packed the tackle bags and after a short rest and a Mars bar, began the 1.5 km slog back to Bridge Sump. By now we were hot in our diving suits and spent a few minutes cooling off in the streamway. Another half hour's grunting and we surfaced at 18:45 after 7 hours underground, determined to return and explore the bits we'd missed out.

After a good feed back at the cottage, we retired contented to the pub.

Graham Adcock.