Jenga vocally connected to River Dove valley!

Last night was another mini-first for the North York Moors.

The Covid Extensions of Jenga Pot, discovered in 2020, have been our focus over the last five years, including digs in the cave which have alluded to a higher level system (several high-level draughty avens and rifts). This led to a temporary distraction at a downstream surface dig to enter this hypothetical section of cave, but as-yet with no success.

We’ve completed the survey, which showed how close the furthest reaches of the Covid Extensions come to breaking out into the next valley west in two places (where the River Dove flows, and itself sinks in several places). This led to a new summer effort at a dig in The Dove itself, at a minor (and dry in summer) sink, which is located about 80m from a particularly draughty high aven at the far reaches of the Covid Extensions (Vaccination Aven), but that too has failed to deliver results.

It became clear that if we were to achieve the valley-to-valley connection (which would be great from a sporting perspective, but would also allow exploration in the Covid Extensions without having to maintain the pumping system at the sumps), we were going to need to focus on one of the branches of the cave that comes very close to the surface.

The simplified survey is shown below, with Tree Root Chamber at the southwest end.

(You can download a full resolution version of this from the York Caving Club publications page).

Tree Root Chamber, the branch at the far southwest of the system, was an obvious target. Small roots emerge through the muddy roof of this chamber, and there is a fresh organic smell. Getting there involves a long slog, through the Jenga Sumps, down Pandemic Passage and along Next Slide Please, which is all good and enjoyable caving. The final 100m however is flat-out wet canal passage, thick with mud, which gives a complete soaking.

The final obstacle is a small chamber which is essentially a wide U-bend and which pools water. Crossing this chamber involves a tight squeeze over a slab at water level and then an immediate face-first plunge into 30cm deep water for a low airspace duck underneath a second slab, with an awkward contortion between them.

At the opposite side of this acrobatic U-bend the passage rises and continues for about 20m, passing numerous tree roots, with a boulder collapse emitting a slight draught, and the walls and roof being nothing more than boulders suspended in thick dense mud. The survey shows this to be at about the same altitude as the field in the next valley, and that it comes within 10m from emerging from the descending slope of the valley.

But the survey could be wrong. It is several hundred metres of surveyed passage from the Jenga entrance, much of it in horrid surveying conditions, so there could be error, plus the overlay with the surface could introduce error too. We were happy to accept that Tree Root Chamber could be up to +/-15m further away from the nominal location. If we wanted any chance of a connection, we would need to pinpoint this more precisely.

Last night saw this effort finally happen. The Jenga sumps were finally drained thanks to an investment in a new generator to power the pumps. The process started several weeks ago and was a bit shaky as the sumps weren’t pumped last year, so the pumps had settled under a reasonable amount of mud. We have fitted an ammeter on the surface so we can see what current is being drawn by each pump to help guide what they are doing (a reading of 6-10A means they are pumping, and less than 6A suggests they are pumping dry, and the sump is clear). However, on startup the pumps were reaching a sufficient current to trip the power. After numerous start/cutoff cycles, whatever mud blockage was preventing startup finally seemed to clear and things seemed to run efficiently. Given that those pumps have been in-situ for over five years, pumping mud slurry and frequently getting buried during winter floods, it never ceases to surprise us their robustness.

After meeting at the Excalibur Pot car park and a plan being formed, a team of three of us (myself, Andy Brennan and John Cameron) headed down Jenga, with an instruction to the surface team to expect us to take 45-50min to reach Tree Root Chamber. We took with us a ferret tracker transponder – something that has worked extremely well in the past at other locations – and even more ambitiously a walkie-talkie, in the hope that if the surface team are able to locate us using the ferret tracker, we might even get a vocal connection.

The sumps were well drained, and with careful technique you can get through them keeping upper body dry, by moving at such speed that the bow-wave does not rebound onto you. It was a pleasure heading down Pandemic Passage after two years away, with the worm casts and water having reset most parts of the cave to as if we’d never been there, no footprints or handprints and lots of fresh piles of organic debris in several places.

Within 40 minutes we were at the canals, and in good spirits, so we made quick progress through them, reaching the final U-bend squeeze/duck. I was the only person in the team who had been through this, and I passed it fine, but John and Andy were unable to get their chests through the squeeze, and the intimidating head-first plunge into water straight out of the squeeze didn’t help with motivation. Therefore, Andy and John remained there, while I went through with the ferret tracker and walkie talkie to set things up.

It was interesting taking the opportunity to properly explore and poke all nooks and crannies of Tree Root Chamber, as both of my previous visits here had been at the end of long trips (once when we discovered it at the end of a long session, and the other when we surveyed it, also at the end of a 5hr trip when we were frozen). Being here feeling relatively fresh and comfortable was a novelty. I pushed myself to the furthest southern reaches of Tree Root Chamber, where there is a 4-5m high mud aven, the highest point and probably the closest to the surface. I was able to dig out a pointy rock, which I used to cut footholds into the mud so I could chimney to the top of the aven where I placed the ferret tracker on a mud shelf. The roof above was dense mud with jammed blocks and nothing solid.

Then I waited, periodically trying the radio in hope of being picked up. Ten minutes and nothing, although I was conscious that we had arrived quicker than expected, so the team on the surface might have only just started looking. Another several minutes later just as shivers were starting to set in, I heard the noise of bang-bang, a crowbar or hammer being banged against the ground outside. We had agreed that there would be a different code at different surface locations, to allow us, if we heard them, to say what we heard in case they did not locate us. In this case, I heard a repeated double bang, followed by pause.

The banging got louder until it seemed to be right above me. Then there was a crackle through the radio. After a little more fine-tuning by the surface team, I was able to get a two-way conversation with them through the walkie-talkies. They had successfully located the ferret tracker transponder and narrowed it down to only 4.5m away. Our experience is that through dense rocky mud, this will likely be an over-estimate.

I then told the team I’d try the ferret tracker another 6m north up the chamber, but nothing was found by the surface team, presumably as I couldn’t get as high there, and this will be another couple of metres under the surface due to the steep slope of the valley.

We headed out, to be greeted by the surface party at the entrance, where we celebrated making the much sought-after valley to valley through trip – at least in audio!

It turns out that the survey and surface overlay was absolutely bang on and the located spot was (annoyingly) amongst a lone cluster of gorse bushes only a few metres up the side of the valley. Most annoyingly, this lies about 5m across a boundary fence into the field, and following a change of ownership several years ago, we have not been successful at getting contact with the new owner (a multi-millionaire who has just built a new mansion on the hills above). The field is not used for anything, and the exact location is amongst a copse of bushes just up a small limestone crag, so we are now going to double our efforts to make contact with the landowner to seek permission to open an entrance.

A superb evening, 100% successful, celebrated by a round of sandwiches, chips and drinks at our regular cavers’ pub, The Crown in Hutton-le-Hole.