December - 2017

The whole team moved up to Camp 5 in the Melinau Gorge on 2nd March 2011.  Over a three day period 49 porters, 10 longboats and 12 expedition members moved up all the equipment and provisions for a month.  Once settled in to surroundings that were familiar for some but a new experience for others, the first job was to re-establish the trail to Whiterock Cave.  This was soon completed and work in Whiterock could begin.

Radio locating

Radio locating Mysterious Ways near the pinnacle track (c) Kevin Dixon

First on the agenda was to set a radio-location point for one of the northern-most passages of the system.  ‘Mysterious Ways’ passage fitted this bill perfectly as it appeared to be the closest to Camp 5 and close to the Pinnacles’ track.  The aim of the exercise was to fix the passage to surface traverses around Camp 5 and therefore confirm the depth of the Whiterock River in relation to the surface Melinau River.  The survex model from 2009 had shown the underground river to be 60m deeper than the surface river but there was some uncertainty of the survey error over such a large loop (12km).  The other advantage of this exercise would be to better confirm the position of all the northern passages in relation to the surface features and, perhaps, assist in the location of a northern entrance to the system.

Preparatory work in the UK had secured the loan of radio location equipment.  The Mulu Caves Project is indebted to Fred and Jimmy Rattray for assistance with this effort.  Not only had they loaned the equipment but also developed a lighter weight model specifically for Mulu and spent several weekends training the team in its use.  The underground equipment uses a magnetic field which introduces a current into the ground and can be detected as a magnetic field again once the current reaches the surface.  By using an antenna, the ‘null point’ can be detected directly over the underground beacon.  Further calculations, using surface distances and the angle of magnetic flux, can be made to give a depth below the surface and hence the location of the underground passage.  That was the plan but could the theory be put into practice over the inhospitable terrain of the Mulu limestone?

A team of four took the equipment underground to re-establish the ‘Flying Monkey’ camp at the northern end of the system, some six hours travel from Camp 5.  At a predetermined time the following day a Hey Phone was used to make contact between the underground team and the surface crew on the Pinnacles’ track.  This communication was essential to co-ordinate the attempt.  Straight away the beacon signal was picked up but for a long time the signal was confusing.  Eventually it was determined that the antenna was below the beacon and the surface team needed to move higher on the mountain.  Fortunately this situation was recognised thanks to the Rattray’s preparations.  Once the antenna team were higher, the null point was soon found, only 50m from the Pinnacles’ track, and the depth established 38m below this point.  Once all the field calculations had been made and tied to the survex model it was confirmed that the surface Melinau River was 75m above the underground Whiterock River.  This is a fascinating phenomenon indeed, and one that should excite karst geomorphologists studying in the area.

GPS fixing

Technical GPS in the middle of the Terikan River (c) Robbie Shone

The final technological objective for the expedition is to establish a series of geodetic (dual frequency) GPS locations along the limestone margins at critical survex stations.  This differs significantly from normal hand held devices, having a certainty of accuracy to within a decimetre.  These will then be used as fixed points from which to attach the survex model with some absolute certainty of both position and, most importantly, elevation.  The two ‘testing’ locations which have so far been successful are the top of a 5m pole in the middle of the Terikan River resurgence and on the fallen tree 50m above the forest floor at the Whiterock Midnight Entrance, which required a cross between rope access and circus acrobatics to establish.

The establishment of accurate GPS points completes a number of technical objectives which have been remarkably successful, considering the conditions.  The laser scanning, radio location, underground communication, the GPS positioning and the ‘big picture’ of Sarawak Chamber could all easily have failed yet have all gone to plan and produced results.

Alongside the technical objectives the team is hoping to explore new passages and caves.  Exploration started as soon as the team settled into Camp 5.  In addition to the camp in northern Whiterock another team re-visited the Hotel California camp in southern Whiterock.  This three day camp aimed to clear up the last few remaining leads in this area; a ramp climb off ‘Lowland’ and a small passage in ‘Api Chamber’.  The ramp was strategically positioned to gain access to the high level passages which must exist beyond the chokes of Api Birthday and Apprentice passages.  A successful climb gained several hundred metres of passage but led to the already known Janet’s Way, instead.  The Api chamber lead didn’t go far either, nor did the few other possibilities left by the 2009 visitors to this part of the cave.  With only half a kilometre in the survey book the southern end of the cave has been detackled in favour of better prospects elsewhere.

Stal in Whiterock river

Gour pools end a promising lead in Northern Whiterock. (c) Andy Eavis

The northern exploration team fared much better.  On the radio location trip the ramps leading down from ‘Lemon Squeezy’ dropped into over a kilometre of passage called ‘Dirty Yorkshire Habits’.  This passage is still going and awaiting a return.  The next camping trip dropped the pitch into the Whiterock River where the team split, one going upstream and the other downstream.  The downstream team added 1.8km of southern trending river passage onto the 2009 discovery before the passage sumped close to Rudang Gallery in Blackrock.  The upstream team surveyed over a kilometre in an oxbow back to the main passage.  Other leads north and east of Pointless Junction yielded half a kilometre and were pushing towards the gorge and the fabled ‘Northern Entrance’ before time ran out.  One possibility remains in this area but the team do not expect to find a way out.  The distance between this lead and ‘No Country for Old Men’ is still 62m!

In addition to work in Whiterock a cave was discovered up the Melinau Gorge.  Red Tip Racer cave was surveyed for 460m and showed signs of major development at this level.  In other efforts across the river, the Gawai feature has been located in the northern end of Gunung Benarat.  This has not yet been descended but hopes are high that the steeply incised walls may have truncated cave development in this area.  Time and further effort will tell.

Helictites in Whiterock

Helictites in a new passage off the Whiterock River (c) Matt Kirby

The new survey tally so far stands at 6.5km and the length of the Clearwater System has grown to 181.7km (field calculations only).

Stalagmite flow in northern Whiterock

Unusually yellow formations in northern Whiterock (c) Andy Eavis