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Many successful expeditions have been based at Son Trach on the banks of the River Son. A summary of these expeditions has been given in appendix 6. Two major systems have been explored; Hang Vom and Phong Nha in the Ke Bang massif to the west. Exploration of these systems continue. New caves in the large area of unexplored karst to the north of the Chay River and Hang Vom system were also discovered. The character of these caves differed significantly due to their vertical nature.
Around Phong Nha village.
During the three weeks we spent in the Son Trach/Phong Nha area, we investigated a number of entrances quite close to Phong Nha village.
On our first day in the area we were lucky to be able to get in touch with Mr. Du, a man who has helped us many times, leading teams to Hang Cha Na, Hang Toong and others. He showed us a couple of entrances to the east of road 20, which leads from Phong Nha village to the Ke Bang massif. The first cave Hang Bin Dap led very shortly to a sump. The second Hang Duc, led immediately to a low wet passage, but had a noticeable draught. Sweeney was volunteered to get wet, and confirmed the cave was small, but definitely a going prospect.
We continued on to Hang Tooc, by following a large streambed which is obviously very wet in the rainy season. We left road 20 at Kilometre 16 and after about an hours walk reached a large collapse area. Draughts could be felt in various places between the boulders, but no going passage was found. The GPS showed this area to be very close to the upstream end of Hang E, and confirmed the idea that Hang E and Hang Toi take water overflowing from the Phong Nha river during the wet season. The main river sink for Phong Nha cave is in a large collapse close to road 20. Known as Hang Tron, this is very close to the known end of Phong Nha. On the walk back we checked out a small dry cave that had been used in the war. A short pitch with a small stream below was seen, but with no draught it did not look promising.
We returned to Hang Duc some days later. First we checked out Hang Bin Dap, which proved to be very short and ended in a sump. Hang Duc is a low rift entrance with a small stream entering on the left and flowing into a wide but low pool. A short hands and knees crawl with your chest in the water caused our military escort to have a few laughs. He decided to wait at the entrance for us. The passage opened up into stooping/ walking size, following a small stream which meandered around mud and silt banks. After a couple of hundred metres, the second ‘duck’ appeared. Flat out in mud and water. Enthusiasm was waning a little, this was not typical Vietnamese caving. Andy was at the front and checked things out. As he put it the bad news was the cave continued, the good news was there were no more bats!!
Through the crawl some wading continued leading to the best duck of all! Although not flat out the passage was water filled to about one inch from the roof. With ears full of silty cave water, we waded out into slightly larger cave passage. A tube on the right led for 30m to a choke and stal climb. The main passage enlarged quite dramatically on a sharp elbow bend. A passage on the left led after 15m to a high level choke and a low level inlet crawl. Continuing in generally taller passage with wades shingle banks and a few stals, a junction on the right was reached after about 800m of passage. Downstream continued for 500m of nice stream way to a sharp right hand bend and an unexpected large clear sump pool.
Returning to the junction, a 15m swim in cold water led into a rift and after about 20m, a draughting choke. Although it was pretty chilly in wet clothes we decided to have half an hour of poking about to find an exit, in order to avoid returning through the splendid ducks. Luckily we soon found daylight, and shortly after, a way through the boulders and out to the surface. A short walk back to collect our gear, and Hang Duc was finished. The cave heads towards Phong Nha cave, and no doubt enters as a minor inlet somewhere.
Towards the end of the trip, the owner of the restaurant next door mentioned that he knew a cave. So we went for a short walk across the road to the limestone. He showed us a 10m pitch into a dry passage with some stals. Unfortunately, only 20m of passage to a sump. We named it Hang De (Goat cave) as it had no name and had been found by our guide when he was a child herding goats.