Trip Report - Blacks Mapping Project - May 2009

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The team were part of a CDAA organised mapping project in the Black Hole on the Barnoolut Estate located in Mount Gambier, South Australia. The Barnoolut Estate has approximately 25 sinkholes but very few of them are ever dived. Blacks Sinkhole is freshwater and is approximately 65 metres in depth as a single major tunnel narrowing towards the bottom. This project was to continue from a previous project that had started and been documented many years ago. Valuable historic information was provided by CDAA member Peter Horne and the team used this data as the baseline to continue the mapping datum. The project was to run over a weekend and consisted of various teams with different tasks, to enable the project objectives to be safely and successfully met.

Day One

The first job was for some of the members to put the habitat in as a test run for other operations involving a habitat and for the trimix teams to get experience with using a habitat. Unfortunately due to the steep roof angle, it was not possible to keep the habitat in a stable location, despite numerous attempts. The only way was to drill and dynabolt fixing points into the rock and the team were not willing to damage the cave in this way.

The next task was for the support team to enter the water and set up the decompression tanks at 21 metres and 6 metres. The sinkhole has existing permanent line in it and the second task was for the mid water team to clean up the loose line, so the path was straight forward for the two trimix teams. These guys clean up a lot of the old lines and re-routed some new lines across to an existing datum point.

Trimix team one entered the water late in the day with the aim of following the permanent line to the bottom, checking the condition of the lower lines and searching for any leads that may be worthy of further investigations. Trimix team two entered the water half an hour after the first team with the aim of familiarising themselves with the cave topology ready for their mapping and data logging dive the following day.

Trimix team one surfaced after a great dive. A couple of small leads were explored, but they didn't go any further than what had already been mapped.

Trimix team two had a great dive and confirmed what trimix team one had noticed, this was the first time that both of these team members had dived the cave, so the familiarisation dive was essential so the Sunday dive plan and mapping tasks could be achieved.

Day Two

Day two started with Pete finding that the mask he had left in one of the limestone holes by the waters edge had been seriously eaten by some large and very hungry mask eating rodent. As you can see from the picture at the bottom, it was rendered useless and Pete was now down to his backup mask only. After a check of all other equipment that was left overnight and a hearty laugh for what had transpired overnight, the team were set for the continued mapping work.

The visibility was down considerably from the first day due to activities on that day with the habitat and the many teams taking part in the diving. This made it slower going for the mapping teams. All teams had a similar task, to measure each datum point for depth, take compass bearing of the permanent line and measure the distance between the datum points. A pinger was also used to give side wall, ceiling and floor measurements.

Final Notes

The two days of mapping were a success, as the CDAA now has more accurate data than had ever been gained before. The participants were impressed with the actual accuracy of that original data gathered many years before. The CDAA Science Officer had taken water and soil samples and would take these away for analysis. The datum data collected by the teams over the weekend was inserted into the mapping software by a surveyor and overlaid onto the original data for comparative purposes. He was happy to report that there were no serious errors in the measurements or compass bearings that were taken on the day and this was in full correlation with the original baseline data. This project is part of an ongoing project and not all the required data was able to be taken over the weekend. It has proven to be a valuable training exercise for team members new to mapping and data collection, and they thoroughly enjoyed the experience. Well done to Steve T for organising the logistics and preparing the task lists, it certainly showed how a well executed plan can be carried out when divers are thinking and working in a team diving environment.

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