IT HAS been 45 years since the first discovery of Otter Hole, a major cave network underneath Chepstow Racecourse.

The cave’s entrance was found in 1970, but it was not until five years later, on 27th December 1975, that the whole 3.2km of crawl spaces, passageways, and vast caverns were accessed. The cave starts on the west bank of the River Wye, below St Arvans, and contains many unique formations.

Within the entrance passage is a tidal sump, a body of water which rises and falls alongside the tide of the River Wye, sealing off the cave for at least six hours in every 12 hour period. The sump is relative to the height of the River Wye, the local rainfall, and the strength of the tide, but rises and falls at least six metres.

In 1970 when the original discovery was first documented, David Parker of the Royal Forest of Dean Caving Club (RFDCC) was searching for potential cave digging sites in the area. He met local man George Gardner, who knew of a short 20 foot cave entrance on the banks of the River Wye, where otters were said to be living, leading to the name.

A small fissure in the rock at the back of the cave let out a strong draught of air, which stopped when the tide rose. This was evidence for a cave system below, and an inclination to the tidal sump which sealed its entrance.

It was not until 14th September 1974 that the first breakthrough was made. A small team from the RFDCC, joined by members of the Gloucester Speleological Society (GSS) and Roy Bennett of the Bristol Exploration Club (BEC) had been digging and blasting through the entrance of the cave over the course of the year. After two days of exploration and further digging, 270 metres of cave were discovered, terminating in a strange lake that stretched on beyond vision. This ‘disappearing lake’ was later deemed to be tidal.

It is this tidal sump that goes towards making Otter Hole so unique and dangerous. John Elliott, who was among the teams that first explored the cave system when it was discovered in its entirety, said:

“The sump is sensitive to local rainfall, the height of the River Wye, and of course the level of the tide. To see the disappearing lake means you’re there at the wrong time, so many people don’t see it. But if you are there to watch it drain it has a sobering effect; I’ve watched it in utter silence, as when it drains, trapped air escapes and it seems to play an extraordinary sound.

“Like a Tube train arriving, it has a rhythmic gurgling, and at some points is like a very loud drumming sound. We learnt our lessons quickly in those early days, about the dangers of it. The first team of three surveyors to go in had tide information but were one hour off. They were crawling through part of the entrance passage when suddenly water started coming up through the floor.

“Quickly struggling to wriggle back, they dropped all their equipment to escape. The last two to get out came through swallowing salt water; the water had risen so high it was nearly lapping the entrance at the surface;. The team had mistimed the highest tide in 100 years. Of course ‘time and tide wait for no man’, least of all cavers.”

Digging continued beyond the tidal sump, as a draught had been found again, and followed to an upper extension. It was on December 27th, 1975, that four cavers from the RFDCC broke through into a large upper passage at the very end of the allowed tidal slot, as time and energy were running out. A large passage with beautiful stalactite formations was followed for 200 metres, before it turned right and grew in size and splendour.

The team had found what is now known as the Hall of Thirty, a collection of massive stalagmites and stalactites. The team were forced to turn from their discovery and return to the surface, before the rising tide trapped them inside. During the following months, after severe storms kept cavers out, the rest of the upper passage was explored. Further caverns of unique formations were explored in the upper extension, with cavers performing cross-tide trips of 13 hours.

Roger Bailey, who was part of the team that dug through the start of the cave system, and was in the group that broke through to the upper formations, said of the experience: “It was hard going at the beginning. The entrance to the cave and the lower passageways are covered with a thick mud, much like the banks of the River Wye itself. Digging was difficult as it usually is, as tools had to be brought through the small crawl spaces and passageways.

“When we finally broke through, we went in as far as we could; the formations are so fragile, we tried to keep as little wear on the passage as we could. There’s something about going into the unknown that appeals to man. I think you reflect on it more when you’re out. But to see those formations for the first time, not seen by any man before, it’s tough to really explain those feelings. It felt timeless, and when you turned your light off, it was pitch black.”

45 years on, and the cave is managed by the RFDCC. Caving groups that enter Otter Hole are accompanied by a warden from the club, and because of the reliance on the tides there are only a set amount of slots available throughout the year. During winter months, the heavy rain fall means accessing the cave is even more dangerous. But the difficulty of entering the cave has had a positive effect on its conservation, as Paul Taylor from RFDCC explains:

“The mantra is that if you don’t want a cave to deteriorate, you don’t find it in the first place. Saying that, Otter Hole is 40 years old for cavers, and still in very good condition. We supply a leader to take groups in, under supervision, and part of the experience involves a certain amount of conservation work. But because of the condition of it, to see the formations for the first time is like seeing it on that first trip 40 years ago. That feeling that the first group felt in 1975 is felt by every caver that sees it for the first time, absolute awe and amazement.

“We’re currently filming in the cave, trying to capture experiences that many won’t see even if they do go down; the draining of the tidal sump for example. We aim to release footage in late 2016.

“To be involved with such a cave is a remarkable experience. To think that when Valentine Morris created his Wye Valley walk around Piercefield House and included a man-made cave grotto; below their feet, untouched and unknown, were caverns more magificent than anything they could have made”

For more information on Otter Hole, and caving in the area, visit the RFDCC website at www.rfdcc.org.uk

For updates on the current filming being undertaken in Otter Hole, and to view earlier footage, visit Redhouse productions, Gloucester, at www.redhousefod.co.uk