Fourbanne Exploration Project

The first week of May this year we continued with the Fourbanne project. After two years of covid we wanted to see what the cave looked like.
The plan was to do a radiolocation between sump 7 and 8. However, due to many line repairs which had to be done in sump 6 and 7, which had not been dived for 3 years, this task has to wait until next time.

This week was again a very nice reunion and we would like to thank the local population of Fourbanne and the speleo group ASDC for their efforts and hospitality! We will definitely be back. Enjoy some pictures we took.

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La première semaine de mai de cette année, nous avons poursuivi le projet Fourbanne. Après deux ans de covid nous voulions voir à quoi ressemblait la grotte.
Le plan était de faire une radiolocalisation entre siphon 7 et 8. Pourtant, Il etait necessaire de faire un grand nombre de réparations de fils d'ariane en siphon 6 et 7. C'était la premiere fois en trois ans qu'on a plongée de nouveau ces siphons. Alors la radiolocalisation doit attendre jusqu'a la prochaine fois.

Cette semaine fut encore de très belles retrouvailles et nous tenons à remercier la population de Fourbanne et le groupe spéléo ASDC pour leurs hospitalité et efforts! On reviendra certainement. Profitez de quelques photos que nous avons prises.😀

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Daniel Chailloux Ron Timmerman Jeroen Steinberg Dennis Blom Wethorse Heleen Niels Duikt Cees Den Toom Frans Janssen Marlon Mendonça Dias Frank van Engelen

This year has gone a bit different than planned. A trip planned in April to radiolocate a big chamber we had found last year, between S7 and S8, unfortunately got cancelled due to the corona measures taken at that time. Since then agenda's didn't permit us to plan a new trip.

On the positive side: a nice 10 page overview of the Fourbanne-En Versenne project sofar has appeared in the Karst Comtois 2, a publication of GIPEK (http://gipek.fr/).

The articles in "Le Karst Comtois 2" are about caves in the Franche Comté and include geological and hydrological studies and reports off cave explorations.

For more information on this interesting 200 page inventory or if you want to get one, take a look here: http://boutique.gipek.fr/home/31-le-karst-comtois-n2-9782954824123.html

The topo for the Fourbanne cave updated with the progression during the last trip.
If you download the topo you can zoom in.

Great news. Richard and Ferry explored 220 meters of new cave and added 259 meters to the survey. The new siphon to pass in Fourbanne is siphon 9! Good progress again! More details and a topo will follow later.
In the meantime at the other side in En Versenne last week Stephane Guignard, with the help of diver Christophe Rognon and a big team of speleologists, passed Sump 5 at the En Versenne side and discovered siphon 6. Siphon 5 has been an obstacle for several decennia in En Versenne. So real steps are made in closing the gap between the 2 caves.

Also the French tv-chanel '3 Bourgogne-Franche comté' visited us to do a short reportage on the project. You can see the reportage under the following link. It starts at 10 minutes.
https://france3-regions.francetvinfo.fr/bourgogne-franche-comte/emissions/jt-1920-franche-comte

JT 19/20 Franche-Comté - France 3 Bourgogne-Franche-Comté

We realised the first goal of the current trip: doing a radiolocation of the end of Siphon 6 which we reached last trip. The radiolocations sofar showed that our surveys were very accurate. However, this time we were a bit off for the first time. But now we can use the radiolocation to correct the survey. It appears that the radiolocations tend to end up in funny places. We have been om the middle of the provincial road on an earlier trip defining the exact location while cars were waiting or trying to pass. This time we managed to be under a big pile of s**t :-).
Tomorrow Ferry and Richard will be trying to push and survey siphon 7 which Marlon discovered last trip.

Summary of the April 2019 trip

From the 17th to the 21st of April we had a new try at passing S6 in the Fourbanne Resurgence.

We reached S6 for the first time in June 2017. Since then S6 has proven to be difficult to pass due to: length and depth of the sump, a lot of sediment and the fact that to push S6 involves an underground trip off 1,8 km. This includes 5 sumps, 1,4 km of diving and having to walk, swim, and pass small waterfalls and boulders between sumps 3,4, 5 and 6 with all the gear needed to push.

We also had several set-backs in our efforts to pass sump 6 (bad circumstances, leaking drysuits, problems while transporting a lot of gear like getting stuck in a restriction, being too negative etc.). However, at the same time we also learned a lot while slowly progressing and becoming more efficient each trip. The biggest progress so far had been made in August 2018 by Ferry who managed to put in nearly 150 meters of line in S6 in one go under difficult circumstances.

In February this year we went to Fourbanne, not to push, but to improve the line and to make set-up dives with a lot off gear easier and safer. Notably, by changing some jumps and gaps into continuous line and by replacing the thin exploration line in S3 by a thicker line. In some places we also rerouted the line circumventing where possible tight passages making it easier to swim with a lot of gear. These improvements were helpful this trip. Reaching the 'bivouac' post-S3 with all the gear needed for pushing (a dive of nearly 1.4 km upstream) was quicker and easier than before thus also improving safety.

The set-up this trip involved getting safeties in S2 (by far the longest sump), 6x 8,5 liter and 2x 7 liter tanks to the beginning of S6 and 4x 5 liter tanks to the start of S4 to transport the previous mentioned bottles through S4 and S5. Also a cooker with pans (thanks Elke) was brought to the bivouac for future use and some more food. A cave link was set-up in the bivouac and Jan and Dennis also made anchors in the walls of the bivouac so hammocks can be placed in the future.

During our set-up dives we got a visit from an old buddy of mine, Stephan Mathies, who I did my fundies with ages ago. He made some nice video shots of our project and he got to know everybody iinvolved and what we are about. It was nice to have him around for a couple of days and we hope to see him back in the future to record our project.

On Thursday the 18th Richard and Ferry got the first 8,5 liter tanks from the bivouac to the start of S6 and Richard set-off on a new effort while Ferry waited at the start of S6. Adding his line where Ferry had tied off the last time, after having passed the deepest part at 20 meters of depth, the sump slowly became shallower. Several times, it looked like he was going to surface, and sometimes he did surface, but than it went down again making for a real yo-yo profile. But finally he surfaced on the other side of S6! Richard saw a corridor going on, Post-S6, but it looked narrow. After tying the line off just above water level he turned around.

At about two-thirds into S6 he also found a promising lead which he noted might be worthwhile investigating, especially if the 'dry' corridor post-S6 proved to be a dead end. Richard and Ferry came up in the source eight hours after having set-off. Richard with a big smile on his face showing a nearly empty explorer reel. Due to this quick and efficient push dive we now still had 6 out of 8 tanks for pushing and surveying still available.

Frans and Marlon went off the next day to check the dry part post-S6. On the way back (downstream) they would check the lead Richard had noted in S6. Post-S6 proved to be chaotic with some big boulders, several leads on the left side and a passage which, fortunately, was passable. Following the river upstream a short way through the passage, walking and swimming, the flow suddenly stopped while the corridor and river seemed to continue. This was confusing. However, on inspection, 2 meters underwater near that point, in the bottom, a big whole was found where the flow clearly passed through. And thus the beginning of S7 was found.

Marlon made a primary tie-off well above the river and put the first line in in S7 working his way against the current through the whole in the bottom. He came up on the other side in the river and after swimming for 10 meters had to go down again. The sump then continued at a depth of around 5 meters. However, soon the dive had to be called due to turn pressure. Larger tanks are going to be needed here. On the way back the lead in S6 was checked but it proved to be a small bypass ending up on the mainline a couple of meters further on.

Saturday the 20th the last 2 tanks were used for surveying. Frans had surveyed the first part of Sump 6 in the August 2018 trip. Ferry managed to survey the rest now, completing the survey to the end of S6. We now know S6 is 355 meters long and at its deepest 20 meters.

Let's see what surprises S7 has in store for us. Transporting the necessary gear to continue pushing to the start of this sump is going to be a real challenge in the future.

Thanks again to the people from the speleology club ASDC for their help and for letting us use their large tent as a space for eating and briefing and for the nice dinner and drinks we had together. Thanks as well to the village of Fourbanne for letting us put up our camp in the middle of their village and to Heleen for sharing her photos of this trip and to Stephan for his interest in our project and the video shots he shared. The dive team: Richard, Ferry, Marlon, Jan, Dennis, Frans and Jeroen.

Together with this post you'll see, as a stick-map, a screenshot of the .kml file on google earth and some photos of this trip. The cave has now been mapped for 2.128 meters (and some more if you include the side passages).

Some more scenic photo's after a successful project week. We will give you a detailed report later on, including an updated stick map.

Sump 6 is now passed and we took a peak into sump 7!

Getting ready to become famous

Today, Dennis and Marlon continued the exploration with the rest of the team.