AREA 5: Ban Bon

BB04 Nam Nan (Resurgence of Ban Lay)

This is a rather important resurgence on the footpath leading from Ban Bon to Ban Tat. We believe that the water comes from the sink of Ban Lay, because the flows are estimated as being almost equal. The surveys show that, although there's still a long way to go and they are developing in a different direction, a connection remains possible. However, looking at the general direction of the caves in this area, it is also possible that the water of Nam Nan comes more from the direction of Ban Tat in the South. We haven't checked this southern area, as it seems to lie outside the karst. Moreover, the local people didn't know of any sinkholes in the South.
One can enter this cave by a little duck at the resurgence, but it's also possible to enter by a side passage, some 10m to the south and 5m higher up. This small passage gives way, after a little descent down a rift, to a beautiful and relatively large gallery (4 to 5m wide, 10 to 15m high) where the streamway is found again. This streamway can be followed for more than 450m to a sump under boulders. The passage is high and progression is easy and straightforward. A few little boulders need some climbing, but no real obstacles are met. For the last 50m, one progresses through a nice and regular tube (conduite forcée) to a little chamber where further passage is stopped by boulders. We were able to progress some 20m further through these boulders (one minor duck), but then the passage became too small (not
surveyed). At the entrance of this chamber, a little climb led 15m higher to a fossil gallery (4m wide, 5m high), beautifully decorated, but blocked by concretions some 40m further on (not surveyed). On our way back, we could feel a draught coming in some 250m from the entrance.At this point the gallery is very high (over 30m). We tried to get up, but couldn't find the way on. This resurgence revealed a very nice streamway, but we couldn't find out where it comes from.

BB06 Ban Lai

To the east of the village of Ban Lai, a relatively large streamway, coming from the west, out of a non-karstic area, meets the carbonate rocks (very steep wall) and enters a very large porch (40m wide, 20m high). This water is supposed to resurge in Nam Nan, some 170m lower. (The data on the map are not correct; there is no surface riser further to the east, as marked on the map). This superb cave starts with a very large porch leading into a big entrance chamber, 'Bluff Chamber', where the river cascades down between huge blocks, that one often has to climb down. At the right hand side of the chamber and after removing some blocks, a smaller fossil passage could be followed for over a hundred metres, where it became too tight (not surveyed). Following the streamway, with a climb down a 8m cascade, enters a large and high gallery. This gallery gets lower 20m further on and one can follow the water to the left in a smaller passage (2m wide, 4m high), which leads, after 80m, into a second large chamber, 'Black Chamber'. This name is due to its darkness, caused by the very muddy walls, testifying to the enormous floods that pass here during the rainy season. Just before one enters the smaller passage, a little climb (2m) to the right, gives way to a spectacular and very beautiful, almost circular passge 'Fossil Tube', which also leads into 'Black Chamber'. In this chamber the river runs along the left wall and disappears at the far end between blocks. The way on was found after some searching, down a step into a tight rift, filled up with whole trees. Down the rift a little duck leads to a small canal and another duck. Here the dimensions become bigger again. A little rift, followed by a spectacular cascade (C6), leads to a larger and steep rift, interrupted by a small and low passage; another step (R5) and one enters another large chamber, 'Block Chamber'. The floor of this chamber is very steep and composed of huge blocks. At the bottom the river runs smoothly into a horizontal rift to a sump at a depth of -156m. We spent a lot
of time looking for the way on, but without success, despite an exposed climb (10m) . At this point, we are only 20m above the resurgence of Nam Nan, but at a distance of more than 1 km and it'll require hard digging... or maybe someone would like to try the sump...

BB07 Bo Hom (CO2 cave)

The 0.9 x 0.5-m entrance is in the backyard of the villagers, on a ridge against the rock, and is immediately followed by a pitch of 18 m, which leads into a large master cave. Vince Surveying Bo HomDownstream, the draft disappears in a too-narrow crack. Upstream one can follow a large gallery, 3m wide and 5m high, in which there are traces of a small, inactive river (cascades and rimstone dams). There is very little water in the cave. Some muddy infeeders are encountered, but all of them are dry. After about 250m fom the entrance pitch, the ceiling lowers and the riverbed narrows to  form the first dried-out sump, the bottom of which is covered with coarse-grained sand. One arrives in a large chamber filled with huge blocks, so it looks as if the place is rather small. The second sump is longer (10 m) and contains a strong draft, which disappears just behind the sump in a steep inlet. The sump is quite large, but filled with mud almost to the ceiling, so that one must follow the small riverbed that cut its way through the mud. After the sump the gallery widens again for a while, for about 40 m, where a low passage leads to the "Waiting Room" before the last and hardest sump, which we partially dug out. The first part is quite high, so one can move on hands and feet through the sand. After 10m it narrows, ducks down, and then continues horizontally. When coming back, a pack got stuck in this part (the rigid first aid kit was in the way). Because of the bad air, it took us three attempts to get it out. After the sump, the bottom of the main stream was covered with gravel and mud and there was a serious lack of oxygen (this might be resolved, since we dug out the third sump). From time to time, a little climb is required over sharply eroded blocks and ancient cascades, here and there are some formations grouped together. At the end, the gallery zigzags and getsmuddy. Here we found footprints of a mammal. At the end, the area is almost a perfect circle, where a high cascade mighthave been active. Maybe there is a way on behind the flowstone against the ceiling.

BB20 Nam Tai I

The first entrance of this cave, which turned out to be a large crack, lies close to the road and is a small walk-in entrance with a slope. At the bottom one has to crawl through a narrow passage until a larger area is reached. A draft disappeared behind a rock that projected from the ceiling. We removed the rock by blasting. This led to the bottom of a boulder choke.
Blasting away part of a rock on top made the "Mitterand Squeeze" penetrable for one of us, leading to a larger gallery and a pitch from which daylight came down. Vincent, who went back to search the entrance of that pitch, was guided there by the local kids who, surprised to hear a voice in "another" cave, were enthusiastically yelling "Koen there! The entrance of this 19m pitch also lies close to the road, a little higher up than the first one. Close to the bottom of the pitch an obstruction was removed, leading to another deep pitch, which was not descended because of the very unstable rocks.

BB22 Nam Tai III

The entrance, a crack 1.2m wide and a 8m deep, blocked by rocks, lies at the limestone-sandstone contact at the bottom of a limestone hill in swampy vegetation. At the bottom is a small slope, followed by a squeeze. This is the deepest point of the cave, and from here it goes way up inside the hill. The hanging calcite "false" ceilings and floors are remarkable, as are the many inlets that have filled up to the top. After a climb one passes a second, quite difficult squeeze out of which comes a strong draft, to enter a low (90 cm) meander covered with a beautiful calcite floor; this leads into a relatively big chamber, the highest point surveyed. To the south, there's another squeeze which leads to a pit. We were unable to pass this pit, but probably the continuation lies above the pit. To the North, a descent brings one to a sandy beach, after which another climb brings you at the top of a 10m pitch with a natural bridge over it. The cave ends on the sandy bottom of this pitch, where we found an eaten corn-cob?! This cave is a strange one, most of the time narrow, very beautiful, surprising and sporting.

BB23 Pitch

Go back to the polje, coming from Noong Xom, and follow the valley going Southeast. A heavy trip through dense jungle brings you to a steep hill with manioc fields. The cave starts with a pit, in which a giant tree root goes down. Down the pitch is a gallery which could not be reached due to lack of rope.