The biggest Cave Rescue Operation in Bulgaria in Duhlata Cave 4th-6th December 2010

On December 3rd 2010 at 20:30 a group consisting of of 7 people: 4 of them cavers, 2 teenage girls (climbers) and an 11 year old child, entered Bulgaria's longest cave Duhlata. The cave is over 18km long and is a complex maze on 7 different levels with 8 different active streamways.

The group's objective was to visit "Chastite na Mulniata"in the far reaches of the system. The last 750m to reach these high level chamber involves following the main underground streamway.

The cavers’ biggest mistake was that they did not know about or even expect the heavy rain that flooded the cave later on that evening. They had reached their destination in about 7 hours and when they headed back,judging by the water level of the underground river, they knew that something was going wrong. The water had become muddy and levels were quickly going up. The cavers decided to attempt running back upstream, but half-way they were trapped in rising water.
Luckily there was a gallery about 14 meters high on that place. The cavers equipped several places in that gallery and began to wait. They made shelter for the children as to prevent body  heat loss. The water rose up fast and after 20 hours it was already 12m deep, and the cavers were left with one last meter of airspace. In that time the water level began to go down and after further 20 hours the cave rescue team were able to reach them from the galleries that were already free of water.

The chief of the rescue operations was Atanas Rusev, cave digger and explorer in the area for more than 20 years. From the very beginning of the mission he knew that situation is very complicated due to the trapped group’s deteriorating condition, and also the very limited time for the operation as more heavy floods were to come from the mountains.   Over 1.40 km in length of the underground river gallery had seen water levels from 1m till 20m deep, and still rising even though the main flood had not come down from the mountains yet.

Even if there had been no extra flow of water into the cave system - the water comes out to the surface very slow and water levels would have lowered only by 1m in 30 hours. So every second was of great importance to reach the trapped cavers and  diving operations or drilling were not options at all:
Too far to dive to, with the muddy conditions of the water and the complex narrow galleries.
For drilling - the place is in the middle of a high hill with a depth of  at least 80m to the cave spaces underground and it would have been very difficult to ascertain the right location to start something that could have taken long time.

Atanas came up with a very audacious strategy from the very beginning of the rescue mission and kept it going until the end. The idea was to dig out and release the cave water from the resurgence  springs that are fed by the underground river. The main group of geologists that works in the area stated that these springs are very narrow because of geology, but Atanas had  long established a different hypothesis, due his expertise in exploring karst areas.

He gathered a very strong rescue team that included almost all organizations connected with rescue missions in the country and with heavy excavators began to clean and dig out the springs. More than 60 people were actively involved in the operation and every second was a race with the time and water.

They succeeded in realeasing 10 times more water from the springs than the  average output and the hypothesis that the  springs are not that narrow was proved. For about 28 hours the output of the springs was kept discharging at the 10 times bigger volume that managed to save the dear lives of the trapped cavers. Without this intervention the rising water would have got to the trapped cavers in 26 hours. Instead, 22 hours later all trapped cavers were outside safe. They spent inside 48 hours. Even if the water level had not not reached cavers inside, they would have had to spent inside the cave about further 360 hours to allow  the water to discharge naturally and allow their exit.  Even half of that extra time would have been too much for the groups deteriorating condition.

Knowledge, rescue heroes and pure luck saved the cavers in the most complex and risky cave rescue operation in Bulgaria.



and more to come