Caves of South Wales Dragon

Ogof Tee - Ogof Cil Sanws

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Ogof Tee is an interesting but little visited cave, located near the top of the limestone / gritstone interface and is characterised by large chokes of loose gritstone boulders and low crawls over boulders covered in thick sticky mud.
Length 500m +
Altitude 344m
Grid SO 02641 09114
Ogof Cil Sanws has the longest record of exploration with the cave first being explored and surveyed by Mel Davies and the B.N.S.S. in the 1960s after the entrance was exposed by quarrying. The cave was gradually quarried into, with the current section of cave, meerly a side passage to the original cave. The cave was visited and dug by the Brynmawr Caving Club and then by the South Wales Caving Club, who resurveyed the remaining cave. Later Toby Stuart of the Gloucester S.S. conducted a smoke test in Ogof Cil Sanws, from which smoke was seen emitting from a large gritstone shakehole next to the golf course. They dug there to find a a small chamber with a boulder choke leading downwards from it. The cave was named Ogof Tee, and this entered a large gritsone chamber and a couple of hundred metres of passage. The route through the entrance choke was enlarged and stabilised to to allow a team of diggers to enter the cave and extend it. In 2000 a team of diggers including Tony Donovan, Roy Morgan and Martin Groves engineered a route down through the boulders at the end of the cave to connect it with Ogof Cil Sanws No.1.
Ogof Tee is located on the Cefn Cil Sanws mountain adjacent to the Merthyr Tydfil golf course, from which it takes its name. The cave is approched from the A470 north of Merthyr Tydfil and then the A4054 is followed in the direction of Cefn Coed Y Cymmer. A short distance along is a track and public footpath that heads up to the wildlife reserve and Danydarren quarry. Parking clear of the gates on the main road, the track can be followed up as it zig zags up the mountain, past old limekilns and then followed up to the top. At the second hairpin, the track is followed upwards with other track leading back towards the Danydarren quarry. A gate is passed on the track and then the track switches back in a northerly direction to reach a second gate. Most of the ascent has now been completed and the path leads to a stile and then heads up to the golf course fence. A route north beside the fence is followed until the large rectangular shakehole full of massive blocks is seen just to the left of the footpath. The entrance has a metal lid on the top to keep out sheep and needs to be replaced after a visit.
Central Northern Outcrop Google map showing the location of Ogof Tee and other caves in the area.
Location map - click marker to show entrance photo
Ogof Tee is located beside a public footpath. Ogof Cil Sanws is located in the face of the Danydarren quarry, which is privately owned and is used as an archery range and so will generally not be accessible.
The lid over the entrance reveals a short drop down into a small chamber under the large loose gritstone boulders that fill this shakehole. The route down through the boulders is quite obvious, but great care should be taken as this whole area is very unstable. The choke eventually reaches the side of a large gritstone collapse chamber roofed with large slabs that are peeling off. On the far side of the chamber a route through boulders gives access to a lower section of the chamber and from there a drop down through loose wet boulders leads down into a section of cave passage. This passage is quite muddy and there is a section of fine craked mud floor which the taped route leads you beside. This soon reduces to a low crawling passage, with a section of flat out crawling in wide passage over sticky mud floor before the passage reaches walking proportions for a short distance. The character quickly changes as the route onwards is gained by climbing up on the right to reach a floor of fallen roof slabs, this continues for a distance until the passage becomes a little larger and a junction is reached. To the right a slope upwards leads to a low flatout crawl over muddied calcite to reach a small chamber with no ways off. Back at the junction the route is off to the left, past drips of water falling into a small pool and then over boulders. A slot in the floor can be seen but is too small to get down into. The route onwards is over boulders until a snug gap leads out into the side of a collapse chamber. The taped route leads round to the left to an area where a climb down through boulders leads to a passage. Again the way forward is over fallen slabs an the passage passes over a slot below the slabs. Eventually the passage chokes, but just before is a slot in the floor where a snug route has been engineered down through the boulders. This point marks the connectio with Ogof Cil Sanws No.1 below. The climb down enters the top of a boulder filled aven, that bells out and leads to a short section of passage. This small passage is followed and enters a larger passage with a sandy floor that forms a small chamber. Ahead and to the left under a rock overhang is a section of low tight passage that enters a boulder floored section of passage. The route on is upwards and to the right where e dug route through boulders leads to a junction. To the right a short section of passage leads to a boulder aven, while down and to the left a passage with a small trickle of water in is met. The water appears through rocks to the right and flows into the passage on the left. This is followed where it becomes lower and wider forcing you into a flat out crawl through water and mud that will sump in wet weather. Once through this short section the passage is a little larger for a short while before a swim through sand and gravel reaches daylight and the view down into the Danydarren quarry from the Ogof Cil Sanws entrance.
An 8mm spit is located above the Cil Sanws entrance, while 5m down the slope from it is a hanger and a mallion allowing a rope to be used to protect the 15 m descent down to the quarry floor.
Cambrian Cave Registry for Ogof Tee
Cambrian Cave Registry for Ogof Cil Sanws
Descent magazine | No.135 p12 (1997) | No.157 p12 (2000) | No.162 p9 (2001)
Caves of Wales and the Marches | Anne Mason Williams - D.W. Jenkins | Ogof Cil Sanws
Caves of the Central Northern Outcrop | Tony Oldham
South Wales Caving Club newsletters | No.52 p5 (1966) | No.70 p12 (1972) | No.112 p8-11 (1993) | No.123 p26-30 (2003)
Caves and Caving magazine | No.77 p11 (1997)
The entrance boulder choke in Ogof Tee is composed of massive boulders with large voids between making it one of the most dangerous chokes in South Wales. The low section of passage close to the entrance to Ogof Cil Sanws is low and wet and will flood to the roof in wet weather, taking up to two dry weeks to open up after rain. A rocket tube of emergency supplies is located in the main gritstone chamber below the entrance choke in case of collapse while people are in the cave.
The photographs and information of this page has been provided to help cavers planning trips. Caving can be a dangerous activity, if you are interested in exploring caves please join a caving club so you can enjoy a safe introduction to this sport. Local caving clubs are listed on the links page or you can visit the 'New To Caving' website for more options.
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