Blue Creek Resurgence – Nelson

Blue Creek Resurgence – Nelson

By Steve Trewavas

Crystal clear water, stark rock and undiscovered passageways make for great cave diving. Unfortunately in most endeavours there is usually a down side, and in this case it was the water temperature – a cool 7° Celsius.

Blue Creek Resurgence is located in the Nelson region at the top of the South Island. Here the karst formation is predominantly marble and limestone. The area is renowned for the Nettlebed (24 km in length) and Bulmer (53 km) dry cave systems, which travel deep underneath the surrounding mountains. Tourist and wild caves litter the area and are a Mecca to dry cavers.

Cave divers Keith Dekkers and Kieren McKay had done several initial exploration dives in Blue Creek. Kieren reported the cave dropped to a gravel restriction at 32 metres and then opened into a river passage four metres wide, flowing both ways, explored to a depth of 45 metres.

Several months of planning, 20 kilos of excess baggage and one day of plane travel saw Chris Ross and I land safely at Nelson airport. Waiting for us was an equipment supply kindly arranged by Aquanaut New Zealand.

Access to the dive site is not easy. A casual 20-minute walk up a hiking track soon becomes a wearisome hour carrying dive equipment. The surface lake is enclosed by a small cave, which is entered through a two-metre drop from the dry riverbed. Keiren’s orange line was clearly visible in the crystal clear water.

The aim of our first dive was to establish the extent of the restriction and ensure deeper exploration was safe. The entrance shaft resembles a smooth-walled lava tube, indicative of large water/ice flow in times past. At a depth of 12 metres, small gravel pebbles covered the floor of the tube and appeared to fill the chamber, pushing us ever higher toward the roof of the cave. We reached the tunnel restriction at a depth of 34 metres, 71 metres from the entrance. The restriction, four metres wide and 80 centimetres high, was passed safely. Heading deeper, we swam across several large cross tunnels, which were heading upward toward the surface. Chris led down the third tunnel we crossed, the floor of which was scattered with smooth round riverbed rocks. Heading deeper, we found the orange line tied off in a large room at 43 metres, 120 metres from the entrance.

We spent two weeks exploring Blue Creek and completed nine dives in total. The cave was videoed to a depth of 65 metres.

Dives were conducted utilising stage bottles that were breathed down to half plus 15 bar before turning, keeping our untouched backgas as bailout. The stages always contained the same mix as our backgas. This method is very conservative and enables a diver having a problem to discard the bottle, and resort to his basic backmount configuration. A diver becomes “cleaner” in the water, not having to manage an added bottle when exiting under stress. The technique also enabled us to maximise gas usage whilst minimising the number of gear haulage trips to and from the dive site. Our final dives were conducted using our backmounts only.

The dive is substantial and would be classified as a CDAA penetration site. It has multiple tunnels and several restrictions to negotiate. At a depth of 65 metres, 180 metres from the entrance, the cave opens into two low-arched rooms with a series of tunnels leading off tantalisingly deeper into the hillside. The largest room, which is found at a depth of 45 metres, rises at least 10 metres above the floor but was not explored above 40 metres due to other dive priorities. Several merging side tunnels also beg for further exploration above the 20 metre point. These join to form one tunnel that rises shallower toward a second entrance in the flowing riverbed above.

All maps and underwater video tape obtained is currently being collated and will be forwarded to the New Zealand Speleological Society for assistance with future exploration. I also wish to thank the local Nelson dry cavers for their support and advice.

We would like to specifically thank Aquanaut New Zealand, Darren Lark of Aquanaut Australia, SportsWorld Motueka, Diver Instruction Service and Electronic Power Systems.

Barrie Heard of IANTD Australasia and Matt London of the Thailand Cave Diving Project provided valuable technical advice.

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