Between 8/13/13 and 8/16/13 myself and Preston Sowell conducted a series of dives in a high altitude lake in Peru. The elevation of the lake is approximately 16,000ft/4875m and the surface ambient pressure was a largely consistent 560mbar. Surface pressure was measured on several mornings using a function of the Reefnet Sensus Ultra dive data recorder. The water temperature for the bulk of the dives was 46F/8C.
The purpose of the dives was multifold. One was to document a series of possible human artifacts that had been observed from the surface on previous expeditions. Another was to look for a species of aquatic frog thought to exist in the lake. We also wanted build the parameters for working underwater in this environment, including thermal management, decompression considerations, and the complex logistics of working there.
The bulk of the dives were shallow, averaging 12ft/3.5m, done to document a set of artifacts that had been spotted from the surface previously. One dive, however, was to a maximum depth of 61ft/19m for 20 minutes. As there is a paucity of human data for diving at this altitude, and the current planning software and tables only minimally cover dives in this environment, planning for this excursion was challenging. The desktop version of V-Planner would allow such altitudes, but did not support the complex equilibration regimen we used.
We spent 48hrs in Cusco, at 12000ft/3700m to acclimatize prior to moving up to our field site. We then spent an additional 56 hours at 16000ft/4875m before commencing any diving to further acclimatize and equilibrate inert gas tissue loads with the ambient pressures. Furthermore, we were at 16000ft/4875m for approximately 80 hours before the deeper dive took place. As this allows tissue inert gas (N2) equilibration, even under the longer tissue half-times in the various models, I felt as though we could adopt a conservative, but minimal, decompression strategy for surfacing safely. As I currently conduct all of my NDL dives with stops starting at 50% of my average (or maximum if it occurs at the end) depth, I decided that this was how we would execute our 60ft/19m dive. We would stop at each of 30ft/9m, 20ft/6m, 10ft/3m for a minute then take a slow (one minute) ascent to the surface.
One difficulty of this particular dive is that it involved a 2 mile/3km round trip walk from/to camp and a mile/1.5km surface swim (round trip) from the nearest area that we could get the horses into with our gear. This was not an ideal circumstance, but we accepted it as the site was key to our investigation.
On this dive, the bottom configuration and mission goals kept us from having a 60ft/19m average depth. The average depth was about 50ft/15m, the deepest 61ft/19m, but we still kept a similar schedule. The 30ft/9m stop was somewhat shortened. The 10ft/3m stop was lengthened, in part because we wanted to observe/photograph some of the rich life found there.
After completing this particular dive and making our way back to camp, we were both fatigued. We remained completely DCS symptom free, electing to stay together in the cook/communal tent observing each other for several hours.
We both carried dive data recorders for these dives and I will be downloading and looking at the captured data over the next several days,
The logistics of executing these dives were very complex, beginning with getting tanks from the US to Peru (purchasing and renting tanks was not an option in Peru). We used LP85 steel tanks in part because of the additional volume over an 80cf aluminum tank and in part because of the buoyancy advantages when using a drysuit/heavy undergarment. Getting proper fills in Lima proved difficult as was transporting the tanks from Lima to Cusco. From Cusco, we had 4wd transport to altitude, but the tanks and all other dive gear were carried the remaining distance to the camp site by horseback. From camp the gear was either carried to the closer dive site by human assistance or by horseback to the farther dive site.
For safety equipment, we carried a satellite phone and sufficient medical oxygen to allow for an evacuation under oxygen therapy to the nearest hospital/decompression facility. The availably of air evacuation from the dive site was uncertain. We consulted with DAN prior to embarkation, and were told that they could not predict how they would manage an incident prior to there being one.
In the end, we both feel as though we met our goals and will be spending considerable time analyzing and compiling our results.
The purpose of the dives was multifold. One was to document a series of possible human artifacts that had been observed from the surface on previous expeditions. Another was to look for a species of aquatic frog thought to exist in the lake. We also wanted build the parameters for working underwater in this environment, including thermal management, decompression considerations, and the complex logistics of working there.
The bulk of the dives were shallow, averaging 12ft/3.5m, done to document a set of artifacts that had been spotted from the surface previously. One dive, however, was to a maximum depth of 61ft/19m for 20 minutes. As there is a paucity of human data for diving at this altitude, and the current planning software and tables only minimally cover dives in this environment, planning for this excursion was challenging. The desktop version of V-Planner would allow such altitudes, but did not support the complex equilibration regimen we used.
We spent 48hrs in Cusco, at 12000ft/3700m to acclimatize prior to moving up to our field site. We then spent an additional 56 hours at 16000ft/4875m before commencing any diving to further acclimatize and equilibrate inert gas tissue loads with the ambient pressures. Furthermore, we were at 16000ft/4875m for approximately 80 hours before the deeper dive took place. As this allows tissue inert gas (N2) equilibration, even under the longer tissue half-times in the various models, I felt as though we could adopt a conservative, but minimal, decompression strategy for surfacing safely. As I currently conduct all of my NDL dives with stops starting at 50% of my average (or maximum if it occurs at the end) depth, I decided that this was how we would execute our 60ft/19m dive. We would stop at each of 30ft/9m, 20ft/6m, 10ft/3m for a minute then take a slow (one minute) ascent to the surface.
One difficulty of this particular dive is that it involved a 2 mile/3km round trip walk from/to camp and a mile/1.5km surface swim (round trip) from the nearest area that we could get the horses into with our gear. This was not an ideal circumstance, but we accepted it as the site was key to our investigation.
On this dive, the bottom configuration and mission goals kept us from having a 60ft/19m average depth. The average depth was about 50ft/15m, the deepest 61ft/19m, but we still kept a similar schedule. The 30ft/9m stop was somewhat shortened. The 10ft/3m stop was lengthened, in part because we wanted to observe/photograph some of the rich life found there.
After completing this particular dive and making our way back to camp, we were both fatigued. We remained completely DCS symptom free, electing to stay together in the cook/communal tent observing each other for several hours.
We both carried dive data recorders for these dives and I will be downloading and looking at the captured data over the next several days,
The logistics of executing these dives were very complex, beginning with getting tanks from the US to Peru (purchasing and renting tanks was not an option in Peru). We used LP85 steel tanks in part because of the additional volume over an 80cf aluminum tank and in part because of the buoyancy advantages when using a drysuit/heavy undergarment. Getting proper fills in Lima proved difficult as was transporting the tanks from Lima to Cusco. From Cusco, we had 4wd transport to altitude, but the tanks and all other dive gear were carried the remaining distance to the camp site by horseback. From camp the gear was either carried to the closer dive site by human assistance or by horseback to the farther dive site.
For safety equipment, we carried a satellite phone and sufficient medical oxygen to allow for an evacuation under oxygen therapy to the nearest hospital/decompression facility. The availably of air evacuation from the dive site was uncertain. We consulted with DAN prior to embarkation, and were told that they could not predict how they would manage an incident prior to there being one.
In the end, we both feel as though we met our goals and will be spending considerable time analyzing and compiling our results.
