MAPPING PROJECT 2007 REPORT NO.

Transcription

1 KILSBYS HOLE 5L46 MAPPING PROJECT 2007 REPORT NO. 1 19/20 MAY, 2007 Peter Horne & Richard Harris

2 The 2007 Kilsbys Hole Mapping Project Team would like to express their appreciation to Mr and Mrs Ross and Lora Kilsby for their interest in, and support for, this project, as well as the CDAA for supporting the project's goals and operations. Chris Edwards is also thanked for his generosity in supplying and installing a permanent shot-line which has now been attached to the pontoon with appropriately placed rings for hanging decompression gases (and divers!). 2

3 Introduction After more than two years of planning, negotiation and organisation, the Kilsbys Hole Mapping Project 2007 finally got off the ground with a very successful first weekend on the 19th and 20th of May, With new lease arrangements about to commence allowing increased access and the opportunity for mixed-gas diving in the sinkhole, it was considered timely that experienced members of the Cave Divers Association of Australia (Inc.) study the deeper sections of the site both for our own interest and in preparation for future diving to be done there. Recent 'GoogleEarth' aerial view of Kilsbys Hole clearly showing the shed and the cut access ramp: S , E The original mapping project was conducted over two weekends in 1983 by a party of air divers comprising the inaugural members of the CDAA's Research Group (CDAARG), namely Peter Stace (Coordinator), Robin Garrad, Jenny Hiscock and Peter Horne, assisted by Martin Garrad, Peter Girdler, Ian Lewis and Phil Prust. That brief but highly-focused effort resulted in the production of a relatively high-quality map which was based upon a number of survey lines down to around 40m but which also necessarily left a significant part of the cave only sketched-in. The May 2007 dives involved a core team comprised of experienced mixed-gas cave divers Richard "Harry" Harris (Project Coordinator), John Dalla-Zuanna (a.k.a. "JDZ"), Chris Edwards and Grant Pearce along with air divers Peter ("Puddles") Horne and Ian Lewis. During this first weekend Victorian cave divers Peter Browne and Scott Edwards also assisted on the Sunday morning. A combination of side mounts, back mounts and closed-circuit rebreathers were used over the weekend, and the eight divers undertook a total of 22 dives during that two-day period. Project Activities The principal objectives of this first weekend were to relocate the old main reference stations A, B and C (shown on the old maps as being at depths of 40m, 37m and 45m respectively in 1983 and thus around 38m, 35m and 44m during this study because of the lowered water-table) and to set up a series of survey lines which would later be used for both shallow and deeper (mixed-gas) exploration and survey work, as well as to identify and explore the sinkhole's deepest areas.

4 The original detailed mapping data from the first project unfortunately could not be relocated by the current project team and is believed to have been lost over the years, so it was fortunate that many key measurements and plots of survey lines and stations had been written and drawn on those first maps, thus making it possible to plan detailed dives to some extent. Prior to the commencement of diving activities, a new reference nail was placed on the sinkhole's western lip from which a dropline was lowered to the lake's surface before being dropped to the bottom of the sinkhole at a (water) depth of 25.4 metres. This station, along with several other areas of interest such as the corner fence posts surrounding the sinkhole, was later located via GPS for future reference, and a length of rigid hollow plastic tube was later tagged as Reference Station 00 for the purposes of this project and lowered to the sinkhole's floor from this point. The divers' vehicles and a view of the cut access ramp and sinkhole entrance (RH & PH). View across the entrance showing the location of the new nail for the new Station 00 (PH). 4

5 View facing roughly west, showing the location of the new 00 nail and the general structure of the sinkhole's entrance (PH). Looking down into the sinkhole from the western side; note the old level gauge now suspended completely out of the water (PH). The water level below the lip of the sinkhole was measured at metres, which is almost exactly two metres below a water-level staff gauge which read metres during the first study of the sinkhole in 1983 and which is now suspended some distance above the lake. 5

6 The divers involved with this study: (left) Grant Pearce, Scott Edwards, Peter Browne and Chris Edwards (RH); (right) Project Coordinator Richard "Harry" Harris (PH). Peter Horne and Ian Lewis; JohnDalla-Zuanna (RH). Dive 1 Saturday 19 May 2007 The weather was absolutely abysmal the first day as everyone geared up, with frequent torrential squalls and high winds whipping across the paddocks. Harry and Grant descended first and swam to the old survey tag C, at the top of a flattish boulder close to the deepest known area of the sinkhole, where they dropped a spare (air) scuba cylinder before tying off and moving to the closest wall, from where they commenced checking out numerous deeper holes on the right hand side to a maximum depth of about 58 metres. They then moved up and to the left (i.e. towards the entrance) and followed the wall down again where Harry then carefully negotiated a rather tight restriction while Grant assisted at the entrance. This bottomed-out at about 63 metres, where Harry dropped the guideline reel before commencing their ascent. 6

7 "Welcome to Mount Gambier!" Grant and Chris enjoying the cold, near-horizontal rain (PH/RH). Looking up towards the entrance ramp from the recently-installed pontoon (RH). 7

8 JDZ and Chris preparing for their mixed-gas dives to around 60m (RH). Chris followed the south-eastern (i.e. left) wall during his descent to check out a rumoured 33-36m hole which was believed to lead to a deeper area of the sinkhole without too many restrictive areas. He located one hole which seemed to fit the bill and dropped easily to around 59 metres where he encountered Harry and Grant below. He then explored all of the other apparent holes along the wall, but found no further obvious leads. JDZ went to C where he connected a line to a rock near the peg before running it along the wall in a clockwise direction, near the wall/floor interface. He swam beneath an overhang area and up through a hole, then followed the wall back towards the entry platform. He tied off the line to a boulder about a metre from the wall (later called station A1) and then ran a tape back along the line towards C for a distance of about 98 metres, which is the upper area of the hole mentioned above. Ian and Peter descended to the new 00 station, where Peter untied the lead weight from the vertical dropline and pushed the tube firmly into the bottom before measuring the depth and swimming into the main cavern towards C. From the original map Peter and Ian expected to find C at around metres, but the map soon proved to be incorrect because when they reached it, their depth gauges indicated that it was in fact at a depth of 46 metres. Peter quickly hammered-in a galvanized nail and attached a bright yellow plastic tag before swimming off for about 23 metres with a fibreglass tape reel to try to locate B while Ian held the end of the tape at C. Peter soon located a peg with lines attached at about the right depth and distance from C and signalled to Ian, but when they both got close enough to read the partially-buried tag they found that it was in fact station B1, and it had a totally-rusted piton-top attached (the original 1983 survey pegs located during this weekend were found to have almost completely rusted away, with only their looped tops remaining in some cases). 8

9 Ian and Peter briefly searched in a vain effort to locate B before they moved across to A and then ascended, noting wall features along the way, including a small horizontal passage at a depth of around 21 metres which Ian entered and explored for about 5 metres or so before it became inaccessibly-tight. Peter and Ian getting organised between squalls (RH). Dive 2 Saturday 19 May 2007 Peter and Ian ran a new orange guideline from a large open reel from 00 to A (at a depth of 37.6 metres, as expected) before following a yellow line (from an earlier project) up to an unmarked peg off which other lines had been teed off, at a depth of 35.3 metres (again, as expected and almost certainly B). They then moved across to C where they tied off the line and they then took turns hammering in a steel tapered peg (courtesy of Chris Edwards). Despite this effort and the fact the peg was pushed into the limestone by more than three quarters of its length, it was still far from secure. Ian and Peter then ascended and noted a number of other old lines running up to an old dropper which was about 4m uphill from the new 00 station; these needed to be removed to avoid confusion later. During decompression they also found one particular hole in the wall containing a considerable amount of potentially-important (probably avian) bone material which has already been slightly disturbed; it is felt that this should be carefully removed and forwarded to a qualified palaeontologist sometime in the near future. JDZ went back to A1 and headed around the wall in an anticlockwise direction, starting a line survey involving the collection of angular, distance and depth measurements along the line/tape at each point of contact or change in direction. He also took mental note of a few deeper areas worthy of exploration 9

10 and found one particularly-promising hole. He then wound the tape back to A1 before returning again to the 98m tape point, where he reconnected the tape to the line and dropped down and back to the line tie-off point near C, where he left the tape reel. Harry went back to the area below C where he pushed extensions to both the left and the right (about 2m and 5m penetration respectively), again around the metre mark. He intended to leave his line for further surveying but when he attempted to cut it, he dropped his shears/scissors (borrowed from Grant) and was unable to relocate them in the zero-visibility conditions that ensued. He therefore untied the line so that he could reel back out; he named this area the Scissor Room. Chris continued to explore all possible holes on the left (SE) wall to check whether any of them led to a deeper chamber; he confirmed that the most likely hole actually connects with the area accessible from below C and thus to the area explored by Harry and Grant on the first dive. He also had a brief look in two holes on the opposite (NW) wall, and secured his vertical shotline to a limestone block below the entry pontoon. That evening saw the team filling tanks and enjoying Grant's hospitality at "Pine Tank Dive Lodge" in Glencoe and going through the data so that plans could be made for the dives the following day. Harry refilling his cylinders while JDZ (seated), Grant and Peter Puddles discuss aspects about the mapping dives (PH/RH) 10

11 Dive 3 Sunday 20 May 2007 The weather was much kinder for everyone this time. Scott and Peter B descended first and went down to 00 where they measured the depth as 25.3 metres (24.6m top of PVC tube) before swimming down to A1. There they attached a new tape and swam anticlockwise along JDZ's line back to 'tapepoint 98' (i.e. the end of the other tape), with Peter pegging the tape to the line as Scott ran it out so that Chris could use it for surveying-in any major holes and the floor/wall interface. At a depth of about 45m they left the tape reel and returned to A1 to tie-off the survey line. Chris then started at the 98-metre tape point (about 47m deep) and then worked clockwise, checking out every feature and noting the depth below the tape at regular intervals as well as the wall distances and ceiling heights etc. He finished back at the 48m tape point and also noted the depths at 00 as 25.1 metres (floor) and 24.7m (top of PVC tube). Harry and Grant went back to C where Harry showed Grant a new area to explore (to the right of the Scissor Room). Harry returned to the Scissor Room where he laid a permanent line (thin orange) and pushed a metal tent peg deep into the silt to anchor it. He relocated Grant's lost shears and surveyed out whilst measuring depths and noting compass bearings, but just estimating distances. Maximum depth found was about 64 metres. Grant checked out the hole to the right of Scissor Room, got to about 52m but found no apparent extensions. He went back to C and turned right again, and 8m from C dropped directly to 57 metres to check a floor hole about 1.5 x 3.5m in size, at 49m. This appeared to be more horizontal and was still going down into a smaller area (side-mounts were needed for this exploration). Ian and Peter H descended to 00 where they tied off their orange line reel and swam down towards C; Ian stayed up much higher while Peter tied off at C, and then Ian descended to try to get a straight-line distance from 00 to C so he could put three knots in his line for measuring back at the surface. Ian wasn't sure that the line was running straight but it was hoped that the knot distance would be very close to the original survey anyway (unfortunately it later proved otherwise; Ian's knots showed a distance of 55 metres (51m horizontallycorrected, which was 5-10m too long to fit on the old map). Peter held the reel end of the tape and positioned himself on C so that he could observe Ian while he swam across the chamber uphill towards B (tape distance C-B was 22.1 metres), and he noted JDZ coming up from below and to his left before returning his concentration to Ian. Whilst stabilizing himself for this measurement Peter felt something brush against his left hip but thought nothing more of it; unfortunately JDZ had a somewhat different perspective (see below). When Ian was out of sight and upon receiving two or three short pulls on the tape, Peter reeled up to Ian at B, only to realise he had left the hammer and attached tags back at C, so he quickly returned to retrieve them before going back up to B and nailing in a tag. While Ian put two knots in his line (00-B distance) Peter untied and cut the old yellow B-surface line and the old A-B line (another yellow line running from B to the wall somewhere above C was left in place as it couldn't be reeled back in during this dive). Ian then moved to A and Peter noted the B-A distance (13.5m) before moving across to A and tying on another yellow tag. Ian spent a minute or so untying the old yellow line and putting a single knot in his line (00-A distance) before they both then swam back up to 00, where the loose lines attached to the old 11

12 dropper-peg were then laboriously hand-wound in by Peter before ascending to the first decompression stop. Ian spent the next half-hour noting various wall and structural details of interest. JDZ went back to C where he dropped to 50-55m and checked out some of the deepest holes. Within 20 metres of C he reached the start of the overhang/ swimthrough and found two deep slots; the first (8m from C) was a vertical fissure 0.8m x 1.5m in size bottoming out at around 53 metres, and the other, about 16m from C, dropped to 57 metres where JDZ thought he would be able to easily turn around without going deeper (bottoming-out at around 60m). However as he turned right, a shower of loose rocks came down and he had a few anxious moments as he supported the rocks while throwing them off to his left and moving towards the exit to his right. He then ascended into the area near C where he encountered yet another rock-fall (caused when Peter brushed against the second tie-off rock near C while he was engrossed in the task of noting tape-measured distances as described above). This rock was restrained by the line that was tied to it, so JDZ resecured the line before surveyed back for the remaining 28 metres (i.e. to the 98m line point) before ascending. Dive 4 Sunday 20 May 2007 Harry and Chris spent this final dive tidying up, retrieving cylinders etc and taking some photos of features which might be of interest for this report. Unfortunately by this time, the visibility had deteriorated to such an extent that nothing especially useful was captured on film. JDZ took some video of the wall around the line and collected his tape measure. (RH) (PH) 12

13 Project Outcomes and Recommendations It is important to report that no obvious deepwater cave area was found during the first phase of this project; the bottom team only barely exceeded the maximum depths recorded by earlier research teams (i.e. about 63m) by just a few metres. However there remain a few deeper areas worthy of further assessment and more exploration is also especially required to the SW of C and along the back wall, because no doubt the oncoming wave of trimix divers will push every nook and cranny. The "shallow" end of the sinkhole also requires more detailed examination for possible leads. An orange survey line has been left in the cave connecting 00 with A, B and C, and another orange line also remains around the back of the cave to aid the wall/floor survey there. A number of discrepancies between the original 1983 map and the May 2007 measurements need to be addressed, especially with regards to more thoroughly resurveying the loop 00-A-B-C-00, and much of the old line has now been cleared out except the long yellow line which heads down from the old survey station in the shallows to the wall behind C and possibly a line running from B to the wall above C. The surface-to-c line is well known to most Kilsby divers and is a useful guide throughout the cave, hence why it has not been removed. The team expects to return on at least two further occasions to add more detail to the survey and to continue exploration work. Much of the deep section is best suited to side mounts, and some areas contain a few loose rocks, so all deep divers need to take care. Measurements Summary Survey Station 00 Nail: Western edge of sinkhole, 8.3m from closest edge of small original roof-hole and 5.2m from corner of largest (main) hole away from shed. 00 Nail to Lake Surface: metres. Station Depths 00: 25.4m (PH) 25.3m (SE) 25.1m (CE) A: 37.6m (PH) B: 35.3m (PH) C: 46.0m (PH) Measured Distances (Tape) A-B: 13.5m (PH) B-C: 23.1m (PH) Knotted-Line Measurements 00-A (43.5m*) 00-B (42.8m*) 00-C (55.0m*) (* Approximate only) 13

14 APPENDIX A Plan View Highlighting Survey Data & Discrepancies The red dots represent the rough positions of A, B and C based upon knotted-line measurements only; they were not physically followed to ensure that they ran clear of obstacles, and the 00-C line at around 55m length is especially suspicious because after conversion to horizontal distance, it falls outside of the current map. Purple lines indicate tape-measured distances between the three pegs and are accurate to within at least a centimetre; the dashed line from B to C shows the correct distance of C from B (horizontally corrected) as is indicated by the arc, so it should be somewhere between the red dot and the original blue circled area.

15 APPENDIX B Harry's Planning Sketch of Key Lines and Scissor Room Pontoon MN New survey post 00 Old survey post Old Yellow Line Scissor Room A -64m B C C New lines left in cave Tagged survey point Cave wall New survey area Kilsby s Sinkhole 5L46, South Australia Plan view Rough sketch showing guidelines and survey marks in cave at 21/5/07. Drawing R Harris. Kilsby s Mapping Project 2007 P Browne, J Dalla-Zuanna, C Edwards, S Edwards, R Harris, P Horne, I Lewis, G Pearce. 15