By Sam Allshorn
Introduction
This report was prepared following a request to the CNCC for financial support of works undertaken to stabilise and prevent further collapse in the entrance of Dale Head Pot. A brief summary of the author's knowledge of works carried out previously is given, followed by the aims of the work, initial assessment and methods used. Although a brief conclusion is offered, this is very limited. It is believed that on-going access to the cave well into the future would be the best possible conclusion.
History
Here is a brief (probably incomplete) history of actions taken to stabilise the entrance, together with comments that lead to the current work. The floor of the daylight entrance shaft was dug for four years by the NPC until a breakthrough in 1975. The dig followed a rift in the corner of the entrance shaft. The end result was a dug shaft (known as the Dig Climb) about 10m deep that was shored for its entire depth. The shoring used in the dig included 4" thick, solid timber boards and lengths of metal bar. The low passage found at the bottom passed around the side of the filled shaft and is called Heartburn Crawl.
Halliwell (2000) indicated that in 1991 part of the Dig Climb collapsed and blocked access to Heartburn Crawl. Brook et al (1991) mention this blockage after describing the passages beyond and thereby created some frustration to would be visitors. The shoring timbers are under a constant flow of water and when the ends rot the timbers move (or fall out) and the dig experiences a partial collapse.
Phil Parker mentioned that at some stage in the 1990s he and possibly Alan Speight had considered asking for permission to re-open Dale Head Pot, unfortunately nothing was done. In 1997 other cavers visited Dale Head Pot to check the state of the collapse. Apparently the floor of the open entrance shaft was cluttered with rusting, long-abandoned, scaffold poles suggesting an aborted attempt at re-shoring by persons unknown. After an unpleasant climb past unstable shoring on the Dig Climb, they reached the floor and dug out 0.5m of debris. However, they were unable to regain the entrance to Heartburn Crawl because they ran out of space to stack the spoil. In 1999 the same group returned to Dale Head Pot. They installed some new timber shoring on several parts of the Dig Climb and hauled up a large quantity of debris. After several long digging trips Heartburn Crawl was eventually regained. Whilst the cave was now accessible it was not by any means in a safe state and the work done had only provided a temporary solution.
During 2006 a group of cavers went to descend Dale Head Pot and managed to reach the entrance to Heartburn Crawl. Paul Swire (RRCPC/ULSA) sent the following to the Not for the Faint-Hearted (NFTFH) website:
"Following an unsuccessful trip to Dale Head Pot during 2006, I can report that the Dig Climb immediately below the Entrance Pitch requires extreme care and almost certainly more work to make it safe. The wooden shoring is under a constant flow of water and is rotting away. At some point it will collapse catastrophically. I'd recommend rigging a rope off a spit at the top to help avoid touching it. At the base of the dig where you squeeze into a flat-out crawl, an unstable pile of debris a few feet high at floor level in the far side of the rift is liable to collapse and block ingress or more importantly egress from the crawl - it would be impossible to dig it out from inside the cave. Maybe some good Samaritans would consider some remedial work here as a nice challenge?”
After a trip was undertaken by Ian Cummins (WRPC), he sent the following comment to the NFTFH website:
“Below the Dig Climb we had to clear a collapse of some decent-sized rocks and timbers to allow a foot-first entry into the notorious Heartburn Crawl.”
Simon Beck provided the following comment about the state of the Dig Climb:
“Myself and Ian Cummins undertook a trip to the bottom of Dale Head Pot on the 20 October 2007. A handful of cavers warned us of the dangerously unstable shaft in the weeks prior to our trip. The opinions I'd received with regards to the unstable state of the Dig Climb were not exaggerated and I was appalled by the suggestion of using the timber sleepers as an aid to free climb the shaft. Both my partner and I dislodged a boulder or two during the descent and a little digging had to be undertaken to access the crawl at the shafts foot. Obviously remnants of a recent collapse, the buried sleepers were testament to this. There was great risk of collapse not only from the 10m above that form the Dig Climb but also the very unstable pile of debris at the bottom of the shaft that could trap unfortunate cavers. It wasn’t until I returned back up the shaft that the more substantial sections of collapse and missing shoring were seen. A clumsy caver wouldn't have to try very hard to cause a considerable collapse, spelling disaster for those now stuck inside the cave (a nightmare scenario for the rescue services) and serious injury or death for anyone stood at the bottom.”
Aims and objectives
The aim of this work was to permanently (at least 20-30 years) solve the recurrent problem of collapse and resulting loss of access to Dale Head Pot - a major Fountains Fell cave system. Considering the potentially serious implications of a collapse and the additional interest the cave may receive due to its inclusion in the latest guide book (NFTFH) it was decided that a major effort had be made to safeguard access to Heartburn Crawl.
Initial assessment
The upper half of the dig comprised large blocks with little shoring other than occasional scaffold poles (often rusty and loose) and some rotten timbers. There was a lack of small material between the blocks. The lower half of the dig comprised thick timber board shoring supported by some metal bars. The boards were wedged horizontally and tended to be rotten at the ends but reasonably sound in the middle. There were some significant gaps between these timbers.
Method
The work has been carried out over three trips with permission. The most noteworthy trip being an exceptionally cold day resulting in hands being briefly and comically frozen to scaffold poles. A slightly different approach was taken to shoring the Dig Climb. Rather than stabilise the areas of recent collapse, it was deemed necessary to shore the entire shaft from top to bottom. Work was commenced from the top of the shaft working downward to prevent those working being caught in any collapse.
Two sub-vertical parallel poles were placed to a small ledge mid-way down the shaft. Where possible the vertical poles were wedged behind natural rock features. Horizontal poles were placed behind the verticals with 90° joints approximately 50cm apart (figure 1A&B). The horizontals were placed to take advantage of natural features in the same way as the verticals had been. More verticals were placed behind the horizontal poles (figure 1A). The aim of these extra verticals was to reduce the space between the poles through which large rocks could fall.
Figure 1A (above): looking up the shored entrance Dig Climb. 1st half of Dig Climb from a small ledge. Most of the poles on the left hand side were behind a flake. Other rusty pole were already in place along with rotten timbers.
Figure 1B (above): looking up the lower half of the shaft it is possible that smaller material can fall out some sections of the shoring here but no material that would prevent ingress or egress from Heart Burn Crawl.
Figure 2 (above): looking down the lower half of the Dig Climb. The entrance to Heart burn Crawl is in the lower left corner. The triangle stops the shoring being pushed into the shaft. The scaffold in the middle of the picture is shown in more detail below.
Figure 3 (above): looking down on the walled section. The wall created stacking pass so the entrance to the crawl could be made more spacious and provides further stacking space for small material that may get dislodged.
The lower half of the Dig Climb shaft was shored in a similar fashion to the upper half (figure 1B). However, the lack of natural features to place poles behind caused some concern. If a collapse occurred in the lower half of the shaft it could push the new shoring into the small space at the bottom of the shaft. To counter this problem, a scaffolded triangle was built 2.5m above the floor to stop the vertical poles moving out into the shaft (figure 2).
A 1.5m high wall was created opposite the wooden shoring to provide a wedge at the foot of the vertical poles to act in the same way as the scaffolded triangle above (figure 3). This wall also created a useful space to store spoil dug out from the entrance to Heartburn Crawl which would otherwise have had to be hauled up to the top of the Dig Climb.
Purchases
The following list indicates tools and materials purchased for the work.
- 2 scaffold spanners
- Galvanised scaffolding poles (2nd hand)
- Drop forged joints (2nd hand)
The total cost was £499.67 including VAT (see attached receipts). Since 20 four foot lengths of scaffold pole and 40 joints were not used the total cost of materials used on this project was £400. NFTFH has donated £200 to this project as a conservation effort directly related to the book. The total sum requested for this work from the CNCC is therefore £200.
Access
Access to the fell is via the already accepted CNCC agreement in place for Fountains Fell. All visitors should deliver their permit to Mick Atkinson at Dale Head House and should not park on the lane to Dale Head House but in the parking area beyond the cattle grid.
Conclusions
The work carried out will hopefully prevent any further collapse and ensure safer access to Dale Head Pot for the next 20 to 30 years. Figure 4 shows the before and after shots. The surface shaft was also cleaned of all rotting timber and short rusty scaffold that had been abandoned. Numerous bits of fencing wire and plastic sheeting were also removed. Any financial support for this work that the CNCC are able to provide would be hugely appreciated.
Figure 4 (above): Shows the Dig Climb before any work and after work was finished
Acknowledgements
The author would like to thank the game keeper Mick at Dale Head House for granting permission to access the land and use the lane to transport materials and Prof. Simon Botterel of the University of Leeds, for the load of generator and angle grinder. The author would also like to thank the cavers that gave up their time to help with the work and for their contributions to this report: Simon Beck (WRPC/CPC), Phil Parker (WRPC), Mike Cooper (RRCPC/CPC) and Paul Swire (RRCPC/ULSA).
References
Brook, A. et al Northern Caves Volume 2 (published in 1991) page 51.
Halliwell, R. Journal of the BCRA Speleo-History Group Record No. 5 Spring 2000