Anchor replacement works - Sell Gill Holes
A huge number of P-type anchors were installed in our region in the 1990s during a prolific project by the CNCC's Technical Group. This saw most of the classic northern pots anchored, and eliminated the proliferation of a diverse array of less safe and durable anchors that was starting to blight our pitches (often referred to as 'bolt rash') and provided an alternative to spit anchors, many of which were starting to show serious defects.
Today, CNCC is still actively involved in brand new installations, including some of the more esoteric potholes that were not tackled in the 1990-2000s, as well as new discoveries. The IC anchors we use today are slightly different, but the overall process, workload and volunteer dedication remains the same.
One issue that has arisen from the earlier installations is due to the size of the holes (18 mm) needed for the P-type anchors. Over the decades, slight shrinkage in the resin in such large holes has manifested as slight movement in the anchors. For some time, we unofficially advised that a small amount of movement (1-2mm rotationally) was acceptable, if the anchor showed no signs of in/out movement, although this was based only on limited evidence, and had always been a contentious assumption which raised a few concerns.
The BCA's new anchor policy, published this year, is clear that any visible movement of anchors whatsoever is unacceptable.
For many years, CNCC has been pre-empting this, and encouraging cavers to report anchors which show any movement via a reporting tool on our website. Before this year, we'd already tackled several potholes which had received the most reports, including Diccan Pot, Simpson Pot and Swinsto Hole. However, the new BCA guidance has kick-started a more prolific program of anchor replacements, with our team slowly working through years of reports.
As a result of this, you will now encounter more caves with a mixture of older P-type anchors and newer IC-anchors.
Replacing anchors requires the CNCC's custom made puller to extract the anchor. Even anchors with movement still require substantial force to extract them - often deforming the anchor in the process. If we achieve a clean extraction, the original 18 mm hole can be reused. Our newer IC anchors only require a 12 mm hole (for which resin shrinkage should not be an issue) however we have also identified a resin which is rated for reuse of 18 mm holes.
On some occasions, the placement is no longer suitable, or the extraction compromises the rock surface too much (an effect known as ‘dinner-plating’) requiring a new 12 mm hole to be drilled at alternative location.
At the heart of our work is achieving a balance between conservation and safety… never an easy judgement!
Anchor replacement requires even more kit to be carried - the anchor puller and huge spanner add another couple of kilograms to the usual anchoring toolkit! Furthermore, anchor replacement often lacks the kudos of anchoring a new route or cave, and does not get the recognition it deserves.
On Monday 2nd November, Ian Patrick tackled some anchors which had been reported on Sell Gill wet route. In doing so, Ian put a call out to our list of ‘probationary’ installers to see if any fancied some hands-on training. One volunteer, Scott, came forward and got his first experience of how to extract and replace anchors under Ian's supervision, with assistance also from Ian Walker, our Anchor Coordinator.
With Scott at the ‘active face’, Ian Patrick was free to get some photos of the work in progress.
