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C o n t a c t



Cogol dei Siori





The Oliero System is situated in the district of Vicenza, in the municipality of Valstagna. It is possible to get there driving along the Valbrenta, passing by Bassano del Grappa and Trento, then there is the small town of Oliero. Since more than ten years around the Oliero Sources there is a natural park possible to visit from spring to autumn. This system contains two sources about 150 m far from each other. The first one is called “Cogol dei Siori” or “Parolini Cave”, the second one is called ”Cogol dei Veci” or “Cecilia di Baone Cave”. They are the bottom end of a large system with the absorption zone of the Aaiago plateau, situated above. The sources are two of the biggest ones in Italy for their water flow and dimensions. During the floods the Cogol dei Siori has a water flow of 40mc/s and the Cogol dei Veci 100mc/s. In drought Cogol dei Siori has a water flow of 0,80mc/s and Cogol dei Veci 1,30mc/s.

Cogol dei Siori has been studied since 1822 by Parolini (scientist and biologist) who made a botanical garden, transplanting the main flora of the Brenta Valley. In 1830 he transferred into the source the Proteus, a hypogeal invertebrate fully depigmented and completely blind, from the Postumia Caves. Fortunately the conditions of these sources were good and today it is still possible to see the Proteus during the dives.

Cogol dei Siori became a touristy cave in 1832, and it was one of the first caves open to public in Italy. Today it is possible to visit the cave catching a small boat to cross the inner lake, landing and walking around for a while inside the mountain.




The dives into the Cogol dei Siori cave started in 1960 performed by the Friulano Hydrological Cave  Group and the Italian Cave Club Mestre. The two groups dived into the inner lake (about –12m). At the end of the ‘70s the C.O.V.A.S. Group of the Verona CAI explored the gallery until 450m from the entry reaching the depth of –50m. The explorations started again in the summer of 1988 performed by Luigi Casati (Lecco Speleological Group, Lecco C.A.I.) and J. J. Bolanz (Spéléo Club de la Vallée de Joux de la Société Suisse de Spéléologie ).

They reached 620m from the entry and a depth of –55m. They also drew the topography of the first 250m of the gallery. The exploration was difficult because of a strong current in the tunnel. The team came back in February 1989 (a very cold winter), and during a first exploration Luigi Casati reached 710m from the entry swimming just with fins. Then J. J. Bolanz using a dpv got to 870m from the entry and at –63m.

They came back in September 1990 and went on for other 110m (980 total), drawing the topography of 700m of galleries; water temperature was 8°C and time spent under the water was about 5 hours.

There were other attempts to go on with the exploration in 1992, 1993, 1995 but with no results due to the conditions: too hot during winter and too rainy in summertime.

In 1998 Luigi Casati with J. J. Bolanz reached the 1100m of development, getting inside the mountain trough a fracture: it was impossible to climb out of the water because the walls were too vertical and smooth, and there were no places to put the equipment; anyway the room was very big: 5m large, 20m long and high and with the lamps it was impossible to see more because the wall was inclined. There were not important water flows, so the prosecution had to be somewhere else. Maybe, as Luigi had already noticed at 900m from the entry, on the left side of the gallery.

In 1999 a sudden winter flood caused the failure of an exploration being the visibility less then 2m with a too strong current.




First call:
For Luigi and J. Jacques the Oliero cave is a challenge. The things they have seen until that moment were full of promises but the weather and other commitments put a spoke in their wheel...or fin! Will the persistence and the care be rewarded? They made some calls to some friends, and then they were ready to try again.

During the first days the team is in front of the source ready to start the exploration, but we find out that too many years passed since the last exploration and it was necessary to start everything as the first time, for example putting down the new line, cleaning the most dangerous zones from the old abandoned yarns. We spent four days to put in safe conditions the first 700m of galleries. We also placed the decompression bell at –6m.

Unfortunately our days were over, so everyone came back home.


Second call:

The team meets on January, the 15th. Luigi puts the yarn until 900m from the entry, while the others are taking and placing the emergency tanks and the relè for the explorative dive. Maybe it is because of the flue of that period of the year, maybe it is because the day chosen for the exploration is the 17th... anyway Luigi is knocked out for the fever. The main worry is the possibility of a rising in temperature with the consequent melting of the upper snow, bringing an increasing of the current and bad visibility. Fortunately after aspirin and vitamin C, on Wednesday Luigi is ready to go again.

In the source there are two 20l relè, and Luigi starts on the 19th, with three tanks on the shoulders. In the first 160m of gallery Luigi prefers to go on with a dpv no matters the dimensions of the place (7-8m large x 3-4m high) because of the strong current. Then, the morphology changes and there are laminated rocks, 20m long, 10-12m large, and 1m high. Fortunately the water runs into other side galleries, so the current does not get stronger for the Venturi effect. After the laminated rocks the gallery becomes larger and the current is really weak, it’s possible to see that the gallery is 20m large and 7m high. Using the dpv and breathing from the two relè, Luigi reaches the 900m from the entry: finally it is possible to start the path to the unknown. After 30’ from the beginning of the dive, he leaves the dpv and ties up the new yarn going on swimming with the fins. The three 20l bottles on the shoulders are encumbering, not hydrodynamic and do not let to proceed quickly. The speed is also slowed down by the bad visibility (5m) making difficult to proceed into large galleries. After 20’ the yarn indicates that it is 1245m from the entry, and –47m. The gas to carry on is over and Gigi has to come back. The return is easier because the current helps, Gigi does not have to find out the prosecution or to tie up the line. The first deco stop is after 1h20’ from the start, and the dive ends after 6h. Luigi and the team are satisfied but they must go on, there are still some days for exploring. So the team prepares the material for the next exploration. The weather is good, but the sun shines just for a few hours in this valley placed on the north-south axes, and it never reaches the entry of the cave. The Giara Modon Cave Club assembles there two tents with a small stove inside to place our suits in a warm place. Jean Jacques, Luigi spiritual father and the man who taught him everything about cave diving is now 60 years old, but he decides to take two tanks and a dpv to 1000m from the entry: the medium depth is 50m he will breathe a giclette (air with a maximum 20% of He). The new progression is faster because there is only to follow the line.

Friday, the 21st, Luigi starts his dive with three 20l bottles on the shoulders, he passes the laminated rocks and takes two others 20l tanks. Then he reaches the material left by Jean Jacques, changes the relè and dpv. At 1245 he leaves a relè and goes on faster. After about 100m he arrives in a room so large that he must leave the wall that he was following: the bottom is smooth and full of scallops, there are no stones and it looks like to go down. He leaves the dpv and goes on swimming. The hope of going down disappears because the depth is –48m and after 10m Luigi gets in a gallery 10m large, 5m high that goes up. At 1680m from the entry, at –27m and 400 m from the entry, the main reel is over, this means that he must come back. He did not think to go on so much! He comes out from the water after 6h30’. Everybody is happy but the time is running out, during Saturday and Sunday the team replaces the material inside the cave but not the bell. If the conditions will be good, they will get back in February.


Third call:

The year 2000 seems to be great for our group of cave divers. The weather conditions are good, so on February, the 5th, the team is still there to carry on with the exploration. Three days are necessary to prepare the deco tanks (at –35m, 300m from the entry), and the relè for the progression, the emergency tanks, the dpvs for the progression and for emergency. Every time is necessary to study the program of the dive for the known galleries and for the unknown path they would like to see. The decision of the number of tanks and the place where to leave them is the result of years of experience. Jean Jacques and Luigi keep studying the place, the ambient, they discuss and check everything.

Wednesday, the 9th, Luigi starts the exploration. This time he will be using seven 20l tanks; in the relè the gas mix is 20% O2, 35% He, 45% N2. On his shoulders he has two bottles with the same mix, and one with 40% O2: if the cave will go up he will use it for the decompression. At 1000m from the entry he leaves the big dpv and starts to use the small one; breathing from the relè he gets to 1680, the end of the last dive, where he goes on swimming. The gallery is big, there are on the bottom some rocks fallen from above. The gallery turns left and right several times. The depth is between –15m and –20m, so the gas waste is low giving the possibility to place all the yarn of the main reel. The yarn gets over, and with 480m of new gallery we are at 2160m from the entry, the depth is –15m and the gallery ends with a T (it’s possible to turn right or left). Goodbye! It is necessary to come back to the light, to the air, to the friends. The return is relaxed, at 2000m from the entry I found two proteus asleep. Now the count down: to 1680 the visibility is 3m. The equipment left inside the cave is recovered, Gigi rides a dpv, and the second one is tied up, and there are three 20l on the side. Funny! It looks like driving a truck! But it is not easy to drive this 5m truck, it is necessary to anticipate turns, to balance the load and to prevent descents and slopes. After 2h, finally Gigi starts the deco: the total is 7h, two hours inside the bell eating energy bars. The team morale is high, and everyone is ready to help again, so why not to try again? The new exploration is planned for Saturday. There are again questions about the dive planning, so J. Jacques and Luigi are speaking about that. They decide to put on the shoulders a tank with gas for the deepest points, and two deco bottles: if the gallery goes out, as they hope, their limitation is not to overtake the depth of -9m. The team spends the all Thursday and Friday to place emergency tanks. J. Jacques has to take an emergency dpv at 700m, another dpv for the progression and two 20l tanks at 1250m. Unfortunately during the second dive, on the Friday, J. Jacques has some problems with the trim, so he can’t reach the 1250m and stops at 900m. Friday night Luigi sleeps and thinks about the things to do during the dive, about the difficulties and tries to image the progression. Saturday morning each member of the team has something to do, and J. Jacques is checking everything. The briefing is on a bar tables during the breakfast, laughing loudly and having deep thought. At 9,30 am the last things to do: Luigi connects the canister to the lamps on the helmet, checks the big dpv and asks to another cave diver to carry it out the laminated rocks. Then he prepares some water with integrators he will drink in the bell, the batteries for the electric jacket under the suit to be warm; everything is ok. Before starting to wear the equipment Luigi walks around, discusses with friends and tries to concentrate before this important dive. He often acts in this way, soon the deep breathings will be just a pale memory. He quickly gets over the laminated rocks, takes the two 20l tanks and two reels with 280m of new yarn. He rides the dpv but he can’t find the correct trim so he falls on the bottom, he manages to solve this problem and now everything is ok. He arrives at 700m where he leaves the first relè, he watches the manometers and realizes that he used more gas than the other times. It is not a problem because there are two emergency tanks along the line. When he is going to leave he can not move: he is tangled up by the 3m dpv placed on the bottom, the bar used to sit is blocked between the bottles’ belt and the emergency reel: he has to spend two minutes to solve the problem. He carries on but some negative thoughts are affecting his mind with the idea to give up. But after a few seconds he realizes that everything is safe, as usual, so he decides to complete this exploration. He arrives in the point where there are the two last 20l bottles and the second dpv. He leaves there the second relè and takes the tanks and the dpv. He can not trim everything because the train is too much loaded on the back, so he stops in a good place where he can change the trim and progresses again. After a few metres the progression becomes difficult because there is a 100w lamp on the side of the dpv, he takes it away, now everything is all right. There is again the thought to give up, but once again he realizes that he could solve the problem; he did not waste too much time and all the equipment works again. It is possible to carry on. At 1350m he leaves the third relè, at 1550 he places the big dpv and goes ahead with the small one. At 1700m he leaves the last relè. He gets the 2160m after 70’. This is the point of the last dive: the fork is over there. Now he has to choose the direction, he leaves the dpv and starts to swim in the gallery on the right, it is large, but after a few metres it is closed by a clay mountain. He comes back and tries to go in the left side. The choice is correct, after ten metres in a gallery 4m large and 6m high there is another amazing gallery (10x3) signed by the erosion. He swims into the gallery looking around curious and enchanted. He goes up to –12m, and down to –15m, swimming right or left with more then 90° turns. On the floor there are not many stones, but it is possible to tie up the yarn to some eroded rocks. After 2528m of progression the back gas ends after 90’ from the start. Knowing the entry is more than one hour far away every unexpected event could be a big problem. In addition the most difficult part of the dive will be the return, in fact Gigi has to  take with him all the equipment inside the cave and ride the dpv for 1550m inside the mountain, with the danger of old yarns that could catch and tangle up him. Finally he gets to the first dpv, the visibility is 3m so he has to reduce the speed. He takes the relè and gets to the big dpv and starts to recover all the equipment. To improve the trim of the dpv and the three 20l, he binds two reels and two 100W lamps. Now he is carrying out of the water four 20l bottles, the emergency mask and reel for a the total weight of about 500kg. The decompression begins after 160’. Other cave divers come to see that everything is ok, Luigi receives a visit every 30-40’. He writes on the wet notes, time passes slowly but soon he is out to see the stars.

The duration of this dive is 7h40’.


The Town Council of Valstagna that gave us the permission to dive in the source.
The Gorle (BG) UNTEN GAS that gave us gas (He and O2)
The dpv and other turnery works were made and improved by TECNOSINT srl in Pieve di Soligo (TV)
Ennio Lazzarotto who gave us hospitality in his home

The Team:
Switzerland: Jean Jacques Bolanz, Marianne Hirt, Jean Pierre Schoner, Zdenek Zenkak
Italy: Alberto Bellot, Gianluca Bertoni, Antonio Bresciani, Claudio Carnello, Alberto Cavedon, Michele Cerro, Giovanni Contessa, Ennio Lazzarotto, Gualtiero Naibo, Alessandro Orlandi, Massimo Sala, Antonio Secco, Marco Sponga, Robert Pontarollo, Fire brigade of Vicenza.

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