Location, location, location

Over the past few years the Cambrian Foundation has slowly extended the exploration in Rock Springs at Kelly Park. The current end of the line is at about 1000 feet of linear penetration at an area of breakdown which appears to communicate with the surface, judging by the large amount of surface debris visible (crockery, rusted paint tins, tree branches etc). We knew from survey of the underwater cave roughly where this might be above ground, but there are also a large number of depressions on the surface and it is difficult to know which of these might correspond to the underwater location.

We therefore wanted to try to obtain a more accurate fix for the current end of the line. Mike Poucher was able to borrow Bill Stone’s cave radio location system from the NSS-CDS, and we decided that we would use this to locate two key points in the cave map, one being the end of the line and the other being the end of the large main passage at about 600 feet penetration. It was ‘Dr Kelly Day’ at Kelly Park, so there were plenty of visitors to the spring as well as us.

Renee and I (Andy) would be the dive team, and Mike, Sandy, Rhiannon and Kris would form the surface team. The divers planned to swim the underwater transmitter and its antenna coil to the end of the line, then connect them together and switch on. After a period of 10-15 minutes, they would switch off, disconnect and swim back out to the ‘T’, the second location, where the same process would be repeated. Timings had to be carefully synchronized as there was no way for the two teams to communicate with each other.

Renee and I got geared up, did our pre-dive checks and started into the cave. We were relieved to discover that the flow was not as high as we had feared but the additional drag created by the antenna and battery/electronics canister made progress somewhat awkward, especially in the smaller passages further back in the cave where the flow accelerates through the restrictions. We made good progress and we were about 80 feet from the end of the line when we found that one of our tie-offs in the permanent line had pulled loose (the limestone there is weak and easily breaks). It took us about ten minutes to fix this which made us a little late arriving at the end of the line, our first transmission location. This is in a breakdown area and there is a large rock with a flat top to which the line is tied. We connected the antenna to the canister, switched it on and checked we had a green LED lit to confirm it was working. After five minutes the LED turned red, indicating that transmission had started, and we had another ten minutes to wait to allow the surface team to locate the transmission. Whilst Renee carefully steadied the antenna, making sure it remained perfectly horizontal, I retrieved a reel I had dropped on our previous visit to this room in November 2007.

Eventually ten minutes were up and we switched off, disconnected the antenna and started back out. Unfortunately during the long time we had been waiting at the end of the line extensive percolation (debris dislodged from the ceiling by bubbles) had reduced the visibility to close to zero. For most of the way back to the main passage we had to follow the line by touch only. This should not present any difficulty for a trained cave diver, and it was useful to practice that skill once again. Once back at the T, we braced ourselves between the floor and the ceiling (the flow is very strong here) and set up the transmitter again. Once the requisite ten minutes of transmission had elapsed, we disconnected and picked up our stage cylinder for a leisurely drift out of the cave.

While Andy and Renee were in the water, Mike, Sandy, Kris and I (Rhiannon) were charged with charting their approximate path underwater. We had the ‘cave radio’ receiver with us and we would try and pinpoint exactly where that corresponded to on the surface. Andy had introduced us to the rough place he thought it was prior to diving, based on the mapwork he had done so far and we made sure we were in the vicinity of this in order to receive the signal.

After approximately one hour of dive time, we heard the high pitched sound of the transmitted signal and Mike was on the case. He had to listen for a ‘null’ in the signal which is where the sound drops off momentarily. There were several spots where the signal seemed weaker but by moving the transmitter around into different positions, and tracing how the signal changed Mike was able to work out where the underwater team was. Unfortunately we were a little off in our best guess of where the end of the line was and had started in the wrong position. We were able to trace them by following the signal from the cave radio but this took time and after the predetermined length of time Andy and Renee turned the radio transmitter off – just as Mike had tracked them to their specific location. This turned out to be about 20 yards further into the woodland, in a different ground depression than we had first thought.

The four of us then walked back to the 2nd agreed spot and waited for the signal indicating the dive team had reached the T. This is where the underwater line divides into 2 distinct paths about 600ft into the cave. The signal came through very strongly and very close to where we were standing, and it took Mike only a couple of minutes to identify exactly where Andy and Renee were, 15 feet of water and 30 feet of rock beneath us. We marked where we were with a stick for surface reference and took a GPS waypoint. We walked back and waited for the dive team to exit the cave.

Once Andy and Renee were out, we walked them to where the cave radio had indicated the end of the line and the T was. Roxanne and Joe from the Kelly Park staff were with us and we were all very excited to be walking a few feet above where the dive team had swum only an hour before.

Thank you Seminole Scuba for sponsoring us again with air fills!

Team members:

Andy Pitkin
Rhiannon Pitkin
Mike Poucher
Sandy Poucher
Renee Power
Kris Shannon