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Mulu’98 – the El Nino Year – Edited from an article by Pete O’Neil and Pete Hall in Caves & Caving – Summer 1999

Following up the work of 1996, the ‘98 Mulu Expedition had major plans to extend caves discovered in the Hidden Valley and to continue exploration in the Clearwater system. During four weeks of mostly dry weather in the January / February period of 1998 the expedition explored and surveyed over nine kilometres of new cave passage, exhausting most of the major leads in the Hidden Valley and leaving the tantalising but difficult prospect of opening up the Western Valley for future expeditions. Pete O’Neill and Pete Hall give an account of the expedition’s findings.

After seeing the ‘96 slide show at Tim Allen’s house, I was hooked. The Hidden Valley looked stunning, as did the quality of cave discovered. A year later seven cavers assem­bled at Heathrow to be followed a week later by Matt Kirby and Martin Holroyd. Flying out with Brunei Airlines was interest­ing as they have an alcohol-free policy, although you are allowed to drink your own carry-outs. As soon as the no-smoking signs go off you can hear the cracking of whiskey bottle tops and the hiss of beer can tabs, and to help you feel at home the cabin staff even supply you with glasses and nuts – some­thing to be said for alcohol-free airlines, I thought, whilst rapidly approaching the half bottle stage.
Two days later and we were in the Gunung Mulu National Park, all our land travel arrange­ments being dealt with, as in ‘96, by Tropical Adventure. Base camp was set up on the site of the ‘84 Nasib Bagus camp in the Melinu Paku Valley and was to be our home for the next twenty five days. It was an idyllic spot. Our numbers had now also swollen to 12 with the arrival of Dave Gill to impart his many years of field knowledge and help sup our whiskey supplies. Robert and Syria, both Park guides and good cavers had also joined us, together with Charlie our cook and Tamajarau, our Penan helper, who was a great asset.

The '98 camp close to Nasib Bagus entrance | photo © Matt Kirby

In ‘96 the expedition joined forces with the Sarawak Forestry Department to spend three weeks in the Hidden Valley. They discovered seven new caves and added 10.5km to the length of known cave in Gunung Api. The major discoveries had been in dolines in the dry valley to the south of the Hidden Valley gorge.  On the last day of the expedition Mick Nunwick and Tim Allen established a connection between the newly found Cloud Cave and the previously explored Cobra Cave whose entrance lay only 15 minutes from our camp..We had two possible options for access to the Hidden Valley and our planned Perseverance Cave bivouac; either through the Cloud/Cobra system or overland up the steep slopes above camp. At the end of Cloud Cave was a 37m pitch which had not been left rigged from ‘96, so whichever route we would end up using we would still have to cut the overland route first.  After several days cutting the overland route we planned a big push. Tim, Robert and Pete O’ would continue the surface bash and rig the 37m pitch in Cloud Cave. Starting later, Nick, Syria, Lee, Rupert, Mark and Pete H. were to ferry loads through Cobra/Cloud, hopefully meeting us at the 37m pitch around 3.30pm. The initial climb above camp was very steep and about 900m high, the continuing terrain into the Hidden Valley being one long slog up and over numerous dolines in dense forest with a floor of roots systems, rotting vegetation and hidden drops be­tween the razor sharp pinnacle karst!  On the way across we discovered a large entrance which became known as the ‘Highest Cave in Mulu’ and, after a cursory look, we con­tinued with our primary objective.  Forward movement was rarely achieved without use of a ‘perang’ and by 2.30pm we still hadn’t reached the 4th doline where the Cloud Cave entrance is situated.  We discussed carrying on for a while perhaps until 4pm, and if not successful we’d then beat a very fast retreat before dark By 4.30pm we still hadn’t found the Cloud Cave entrance but by now we were committed either we found Cloud Cave or spent a night in the jungle with no bivy gear. The parangs were now very blunt and our trail became desperate to follow as we slipped and stumbled down dolines.

Syria with the 'cobra' formation in Cobra Cave | photo © Mark Wright

Then, suddenly, we discovered a track mark still visible from ‘96 and ten minutes later we were at Cloud Cave entrance after being on the go for ten hours. But there was no sense of relief. Having been through Cobra into Cloud, and to the base of the pitch two days before we now felt we were on home ground, although there were still a few problems; the others had long since gone, the dumped tackle bags the only sign of their presence. Our equipment was minimal no helmets, one SRT kit, two head torches, both with old batteries, and three cigarette lighters for emergency light­ing. We plodded on through the cave, hand­over-handing some of the pitches, eventu­ally reaching base camp at 8.30pm having completed the first Cloud/Cobra through trip. What an excellent day.
The expedition in the Hidden Valley could now start. While the route over the top was being pushed, Nick, Lee and Mark had taken advantage of El Nino’s dry conditions and pushed and surveyed 610 metres in the Invader Streamway cave which lies below Cobra. Dave Gill and Syria resurveyed Tiger Cave and Tiger Back Cave, the original survey being only grade 2 with no notes.
They also carried out a surface survey to tie in the two caves with Nasib Bagus. A bivouac camp was now set up in the en­trance to Perseverance Cave in the Hidden Valley with groups of four or five spending four days at a time in residence. Bridge Cave, discovered in ‘96, was the first site to receive our attention and a further 3.2km of mainly large, dry passages were surveyed together with the discovery of a new en­trance which emerged in the second doline approximately 40m from the entrance to Arch Cave. An undescended 95m shaft (The Abyss) was investigated and proved to con­nect with the main drag in Cloud Cave. This connection and other discoveries in Cloud brought the Cobra/Cloud/Bridge system to 16.9km in length.
Leads in Cloud Cave were explored and a total of 1.5kms of additional cave sur­veyed, bringing the independent length to 3.7km.
The cave we had passed on the trail blazing day, The Highest Cave in Mulu’, was revisited and pushed to -71 m with 280m of very old passage with all ways on choked. It is one of the highest known caves on Gunung Api at approximately 580m a.s.l.
On the surface in the Hidden Valley a great deal of effort was made to gain access to the Western Valley which runs over known passages in Clearwater Cave. However, owing to the extremely inhospitable terrain work was abandoned only a short way into the valley, faced with heavily vegetated, steep sided dolines stretching away into the distance. While this work was going on, access was also gained to Helicopter Cave, first seen from the air in ‘96 but remaining elusive on the ground to that expedition.
The cave proved to be a large, aban­doned passage which choked completely after 30m and, being one of the expedition’s major objectives, was a major pill to swal­low. Several other remnant caves were dis­covered between Helicopter Cave and the Western Valley, but all were short and choked. The final day of surface bashing had gained only 50m horizontally in approxi­mately 10 hours! —testimony to the impass­able nature of ‘one of the most inhospitable terrains known to man’ (Lyon, 1978).
While all this exploration work in the Hidden Valley was gaining momentum, plans were also being made to push the unexplored Clearwater VI streamway.
Pete Hall covers the expedition’s activi­ties in this cave:
Clearwater System

Lee Cartledge near the end of Drunken Forest Cave | photo © Matt Kirby

Almost as soon as we reached Sarawak Dave Gill was trying to persuade us to have a look at the end of Clearwater Cave even though it wasn’t high on our list of priorities. The upstream limit for several years was sump V, reached in 1988. In 1990 a team had gone for another look on a particularly dry day and found a dry bypass to sump five and reached the Clearwater VI streamway. It was late in the trip so they had returned to their Scumring bivouac vowing to return the next day. But of course by the next day the bypass had flooded and has been flooded on all subsequent visits. This seemed like the ideal opportunity with Northern Borneo in the grips of the most severe drought in living memory due to the El Nino Ocean current. So while the third bivouac was taking place at Perseverance Cave we decided to acquaint ourselves with the part of the Melinau Paku river valley close to Clearwater V in the hope of finding an easier entrance.
The first line of investigation was Drunken Forest Cave, a short, well-decorated cave with characteristic leaning stalagmites as well as a fine array of other pretties. At the far end a flat out crawl led to a handshake connection to Clearwater V. However somebody had already tried to widen it by hammering and our bolting hammer couldn’t make any impression.
A recce of the cliffs above Drunken Forest cave was no more successful and following a bearing Matt had worked out to an area directly over another part of Clearwater V was equally fruitless.

The road to the caves along the Paku river | photo © Matt Kirby

So we set off downstream along the Melinau Paku valley to look for Berang’s Entrance — the principle entrance to Clearwater III. Unfortunately Matt and Syria couldn’t remember it and we went right past. The following day we measured 1200m downstream from a known point on the river and with a bit more searching we eventually found it – quite a small entrance which is only visible when you actually reach it.
We were immediately rewarded with large stomping river passage all the way through Clearwater III, one of the most im­pressive parts of the system. Matt was a bit rusty on his route finding but, with the help of the survey, we found the connection to Clearwater I at Hyperspace Bypass and continued along to Junction Cavern where the lower and higher level routes through Clearwater I unite. Matt assured us that we’d done the hard bit of route finding so we left some spare tackle and carbide and set off out.
On the return visit Nick Jones, Mark Wright, Syria and myself decided to use the Scumring bivouac as a staging post on a push to Clearwater VI. We also had the survey and copious notes provided by Matt. At Junction Cavern we picked up the tackle and after another hour’s progress up and down huge boulder slopes we dumped the camping gear at Scumring — so called be­cause of the tidemark of debris left over from floods. It seemed to have all the prerequisites of an underground bivouac: a large area of hard flat mud, water supply, drains and the thermostat on a constant 26 °C.
Soon we were off across the Snow Slopes of knee-deep, powdery white guano with a draught that can blow your lamp out in a passage 10m wide. It took several hours more trudging through huge caverns over slippery loose boulders before we came to Rampage, a 2m diameter descending tube leading to a 15m pitch into Clearwater V river passage. It was trickier finding the way down to the river itself from the ledge we were on.
The river was mostly thigh-deep wading with very little current for about 2km, a contrast from the descriptions we had heard of pulling yourself along the walls against the current. At about 7pm we reached sump 5, somewhat weary after our journey. The sump bypass was indeed open although it was easy to see why it was normally closed: 100m downstream of the sump was a 15m high boulder pile which usually dammed the water.
We found the final survey station from 1990 and began to survey. After about 50m we popped out in the streamway of Clearwater VI, which was only about 50m long and ended in a large deep upstream sump pool at Sump VI. Upon swimming across we found a steep and slippery climb out of the water which needed some garden­ing to get to the footholds. This led to a dry sandy oxbow and a fork.
To the right climbed steeply but the left way offered a more likely sump bypass so we surveyed a further 150m of gradually ascending passage. Gypsum Crystals on the floor indicated it was flood-proof— quite a comfort after having been in flood-prone passage for a couple of hours and being beyond a sump.
This oxbow choked with sand but 50m from the end was a hole down through blocks with a strong draught and river sound coming out of it. This led onto a boulder slope which in turn led down to a 8m pitch into the Clearwater VII streamway. By this time it must have been going on for 11pm so we called it a day and set off back to camp. The journey back was quite hard work and when we trudged wearily hut contentedly into camp we had been on the go for 16 hours without a break. Syria was especially knackered as her previous longest caving trip had been 7 hours with us in Cobra cave the week before! After a few brews of tuna soup, a welcome break from the end­less spam curry of base camp, we settled down to sleep.
The following morning after breakfast we were fettling lamps ready for our assault on the rivers of Clearwater VII when we discov­ered the error in our planning: we had enough carbide to get out but not enough for another pushing attempt. In a smaller, less complex cave a solution using electric head-torches might have been possible but here plenty of light is essential. There was nothing for it but to retreat. I think some of the more tired members of the team were secretly relieved!
Back at base camp we met the Perseverance Cave team and exchanged news. The following morning we regrouped and gathered supplies for Nick Jones, Martin Holroyd and myself for three days. Martin had been planning to go back up to Perseverance Cave but we managed to poach him, although he was far from keen to be exploring beyond a normally closed sump.
With the cave rigged and knowing the way we were able to reach our previous limit in about six hours. Martin went down and rigged the 8m pitch using a convenient eyehole belay at the head of the pitch while Nick and I started the survey.
The pitch dropped into the streamway in welly-deep water with a large deep sump pool a few feet downstream. Upstream was a small cascade — something of a rarity as the Clearwater river is virtually level through its entire length. Beyond the passage en­larged to 10m wide by 20m high with ankle-deep water flowing briskly over a knobbly floor, a welcome change from the smooth slippery wading of Clearwater V. The 60m tape came into its own and we made short work of the first 400m.
A large passage appeared on the right but it turned out to be an alcove with a black wall at the end. Shortly after was a cross­roads at some large blocks where the size of the river passage diminished noticeably. Then after a further 100m we came to a large, deep, clear sump pool. This was a disappointment as the water is known to come from the downstream sump in Black-rock Cave at least another kilometre away and it is believed to pick up a large inlet on the way.
After a moment to reflect (and in Martin’s case to dream of sump diving) and cram chocolate into our mouths we turned round and set off to tidy up the side passages. The first side passage led off about 50m back. The way spiralled up through big loose boulders then popped out into the vastness of ‘Baby Sarawak Chamber’ a scree floored sloping chamber about 100m across. An alternative exit gave onto a loose 60m scree slope, ‘Stand by to Slip’, which is what fire fighters shout when they slide down the greasy pole. A noisy and nerve-racking de­scent led us back to the main drain at the crossroads.
Directly opposite, a large passage led off apparently along a flood overflow with large slippery cobbles. After a dry plunge pool, which would look awesome with water flowing into it, the passage climbed over more rounded limestone cobbles to end at a solid cobble choke. Another smaller branch at the plunge pool closed down at narrow draughting rifts.
There were no more leads to go at in Clearwater VII so we derigged back to where the one lead remained: the steeply ascend­ing passage above the sump in Clearwater VI. ‘Pearly Passage’ led up steeply past a
nice bowl of cave pearls through a low arch into a chamber where scree was coming from a crumbly, domed roof. As I attempted to climb on up the scree slope I could see a narrow gap between the scree and the over­hanging wall where it was possible to wrig­gle through into the next, larger chamber, also scree-floored. And bugger me if we weren’t looking at a cairn in the middle with a ticket on it ‘Tim and Richard 1991′! It referred to a visit by Tim Allen and Richard Chambers who had approached from the Armistice Series down a pitch, although all they had found was a sump.
Perhaps if they had looked down the narrow and obscure passage we had entered by, Clearwater VI & VII might have been found earlier — who knows?
This rounded off the trip nicely by tidying up all the loose ends in that part of the system. So we set off back to Scumring Camp con­tented, derigging on the way and arriving about 3am.
The following day we navigated our way out through Clearwater I making for a very impressive through trip, although it was somewhat dulled by the weight of our rucsacks. After we had marched up and down the steps of the Clearwater plank walk we were thoroughly shagged out and glad to reach the Sipan Bar. As we refreshed our­selves with cold Tiger beer Matt and Mark presented us with the order of the evening: Dinner as guests of the manager of the five-star Royal Mulu Hotel — and we had half an hour to scrub up before our taxi arrived. We did spare a thought for our comrades in the rather spartan Perseverance bivouac — but only briefly!

The team on the log near camp | photo © Matt Kirby

Pete O again
While the last push in Clearwater was getting underway, Rupert, Lee, Tim and Pete O’ headed back up to Perseverance for a last four day bivvi. We finished all the remaining leads in Bridge Cave and then turned our attention to Perseverance Cave where a 10m high calcite blockage had stopped the ‘96 team.
A long, exposed traverse climb by Tim and Rupert reached the top of the blockage and with a rope rigged we all continued down a further 10m pitch on the far side of the blockage into virgin passage. Six 50m survey legs later, in very large passage, we popped out into the side of the third doline. A large side passage with some superb rock formations was also pushed; in total 600m of passage was surveyed, bringing the length of Perseverance Cave to 1.5km. This was our last night at the bivvi site which had become known as the Betty Ford Clinic due to its lack of alcoholic beverages. It was, however, a sound choice for a bivvi spot, with enter­tainment provided by a family of rats whose home we had invaded.
Our final night at base camp was defi­nitely one to remember. The party went on until very late and even the Mulu Brandy, which was dubbed ‘the most inhospitable brandy known to man’, was consumed. The following day, 17th February, the camp was dismantled and several hours later, stepping out onto the plank walks leading the final kilometre to the Park HQ, the expedition was over. The fat lady had sung an end to a superb month.
The total length of passage explored and surveyed was 9267m, and the length of the Clearwater system is now 108km. Unfortu­nately, all going leads in the Hidden Valley are now finished and the future for explora­tion in this area will lie in the Western Valley. The prospects of pushing into this very remote spot, with no going leads, are not attractive.