Rather than return to a camp in the Hidden Valley, the expedition took a gamble on being able to access the previously discovered caves by an untried route over the surface from the Melinau Paku Valley. A keen sense of navigation and a great deal of good luck were required.
During February 1998 a return was made to the same area to continue exploration. 8.4km of caves were explored and surveyed and a connection was made between Bridge Cave and Cloud Cave to bring the Cobra/Cloud/Bridge System to 15.5km in length and the greatest vertical range of any cave in the Park.
Owing to the logistical problems of supporting an expedition based in the Hidden Valley gorge, and because most of the significant leads were to the south of the gorge in the dolines, it was decided to establish a camp near Good Luck Cave (Lubang Nasib Bagus) in the Paku valley. Access to the caves was initially via a surface route which the team established to the fourth doline, this route had never before been tried and was a significant gamble. Owing to the difficulty of the terrian the surface track was quickly abandoned in favour of the underground route via Cobra Cave and Cloud Cave which had been linked during ‘96. On the overland route a shaft entrance was explored. This was thought to be one of the highest caves t be found in Mulu and was named The Highest Cave in Mulu.
Bridge Cave was connected to the main passage of Cloud Cave by dropping a bag down a deep shaft (the Abyss) which had been discovered in ‘96. In the third doline further discoveries were made in Perserverance Cave which led to another entrance in the wall of the doline. High above the third doline a valley feature heads westwards towards the area of Leopard Cave. Attempts to gain access to this valley proved impossible due to the pinnacled nature of the terrain where only 50m progress was made during a whole day’s exploration. In this area Western Front Cave was found high above the third doline.
In the Paku valley Drunken Forest Cave was re-visited to investigate the connection with Clearwater 5 with the possibility of establishing an easier access to that part of the cave. Although the ‘handshake’ connection was found no way through was possible.
The expedition was in the field during an El Nino year and the Park was experiencing a severe drought. As the expedition was based in the Paku Valley, and water levels were extremely low, it was though to be an ideal opportuity to investigate the Clearwater 5 upstream sump which had been inaccessible to expeditions since its discovery in 1990. During that expedition a sump bypass (Watergate) had been discovered which allowed the team a tantalising glimpse into the darkness of Clearwater 6, unfortunately they had not been able to explore further owing to Watergate sumping off after heavy rain.
Access to Clearwater was made via the nearby Berang’s entrance. As predicted the streamway was low and Watergate completely dry. Access was made to the Clearwater 6 streamway. A further upstream sump was bypassed into Clearwater 7 which divided and terminated in a further sump and a water worn boulder choke wh no apparent way on. On the way out a bypass to the Watergate bypass was found.
Low water levels allowed access to the Invader Streamway beneath Cobra Cave, which forms the resurgence for the cave. Exploration was very difficult in deep water and although 600m of passages were explored no signficant leads were found.
The harshness of the karst landscape in this area of Gunung Api undoubtedly made the two Hidden Valley expeditions the most physically demanding of any in the series of ‘Mulu Caves’ expeditions. Although there is little doubt that further entrances lie unseen, beneath the forest canopy, it is likely that many may never be discovered due to the impenetrable nature of the surrounding landscape.