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Otter Hole

A short article by ROY BENNETT on an interesting recent discovery in the Chepstow area

Background

The cave entrance was found by R.H.B. as a result of the surface survey work being done in the Chepstow area for the Cambrian Cave Registry.  As first seen, it had a strongly draughting bedding plane a little way inside the entrance, and deeper choked extensions.  The bedding plane had been pushed some way by removing some stal deposit, but there were no signs of any recent digging, and work was commenced by the Wednesday Night Digging Team (Phil. Kingston, Colin Clark and Roy Bennett) aided by frequent applications of bang over a period of about two months.

The previous work had, in fact, been carried out by the Royal Forest of Dean Caving Club following a much in earlier discovery by Dave Parker (R.F.D.C.C. and G.S.S.) and they returned to dig more intensively in the deeper part just after the B.E.C. team started work.  The latter were blissfully ignorant of this activity, only finding out when they went into the lower cave to look for a missing bucket and found to their surprise that a big hole had been dug out and a breakthrough made (actually four days previously).  At this point, one of the diggers and party arrived and a rather heated discussion took place, to be continued later by telephone with the result that it was more or less accepted that the three B.E.C. diggers would take part in further exploration.

The Cave

So far, about fifteen hundred feet has been found with possibilities of further extensions.  The entrance series consists of a number of low bedding planes and rifts and is known to flood dangerously in at least one place on very high tides.  A party has already been caught near the entrance by a tide of over 46 feet which caused a very rapid water rise which almost sumped on the last person through.

Beyond this section, the passageway becomes sizeable with many fallen boulders, much mud and some nice but vulnerable stalagmite formations.  This section ends with a sump which rises and falls about 15 feet with the tide.  It will fall to an easily passed duck at low water and is being enlarged by the Forest Cavers.  At present this is a serious trap as the fall in level depends on the weather as well as the tide.  Thus, although several trips of a few hours to the far side have been made, after the very heavy rain in September it failed to open at all for about three weeks, rising to over ten feet above opening level even at low tide.  A probably by-pass is being currently worked on which should remove this risk except under very wet conditions.

Beyond the sump, a boulder ruckle leads to a mainly rift-like stream passage of impressive proportions and very well decorated in parts.  It ends in a large, loose boulder choke which has at present stopped further exploration.

For details of the R.F.D.C.C. digging and exploration etc, see the Royal Forest of Dean Caving Club Newsletter 54 November 1974.