photo: Steve Porter (left), Noel Sloan, and Kenny Broad traverse the Metro in San Agustin in high waters. Photo by Wes Skiles.

After the Peña Colorada Expedition in '84 Dr. Bill Stone set about developing the CIS Lunar rebreather, so that he could mount an expedition to the other end of the Huautla system. This expedition had the primary goal to dive the main downstream sump. The shortest route to this sump was (and still is) via the Sotano San Agustin entrance. It took ten years of development and training, before the expedition could finally be launched in 1994. It was probably the most hi-tech and ambitious cave exploration project yet attempted. With a team of 44 cavers and divers the spent three months in the field.

The team used the newly developed rebreathers to crack sump 1, which proved to be 430 meters long to a small airbell, followed by another sump of 170 metres length. The expedition was to be, this success was marred by the death of cave diver Ian Rolland during the exploration. After a 6 day body recovery exercise the exploration resumed and some weeks later Dr. Bill Stone and Barbara am Ende dived through both the sumps and established camp 6 in the new section of cave. They spent 6 days exploring and mapping the new cave, finding a total of 3.3 kilometers of new passage. They were halted at another sump which they called - sump 9, aka "The Mother of all Sumps"!

The survey data collected showed that the gap to the Cueva de la Pena Colorada was close to 4 kilometres.

Sump 9, a point that may be considered the most remote yet reached inside the Earth.
— Dr. William Stone

Further reading:

  • Stone, B., am Ende, B., Paulsen, M., 2002, Beyond the Deep: The Deadly Descent into the World's Most Treacherous Cave, Grand Central Publishing.

  • Stone, B. and am Ende, B., 1995, The 1994 San Agustín Expedition. AMCS Activities Newsletter 21:44-64. [pdf]