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Ogof Cwmwl Ddu Update #3

This weekend saw the biggest team yet assembled for some digging action. The weather was fine and Duncan and I kicked into gear on Saturday morning by starting to haul scaffold poles up the hill. I’d done one carry the night before but lost enthusiasm when it started to rain and my wet weather gear was at home. A two minute job of sorting out the awkward scramble up from the workings into the shakehole changed from simply cutting some steps to installing a stone staircase. At least you don’t fall down the hill anymore.

On one of our return journeys to the scaff store down near the road we eventually met up with Starfish (aka Tangent aka John Williams), Pete Talling and Fleur Loveridge at 2pm who were our “A” team. Back up the hill the A team got underground to clear Chris’ bang from Thursday and prepare shot holes to dispatch the rest of the boulder. The initial bang had demolished a large part of it but left a couple of rocks that need further persuasion.

Meanwhile, Duncan and I tackled shoring the entrance mud banks which had started to slump into the shaft. By prior arrangement Chris arrived somewhat before we were ready for him, as we’d been late in getting into the place. A cockup with the drill battery extension lead being left in my car was averted when Chris managed to drill the boulders without. Did enjoy the trip down the hill though! We reckoned that it would take 30 minutes to the bang to clear so went up to look at Ogof Hammer in failing light. While Starfish and Duncan had a look at this, Chris and I went back to Cwmwl Ddu, and Pete and Fleur went to get out of hypothermic gear.

The bang had done its job but at first inspection there was no clear way on. A few bucket loads later revealed that the water disappears though a cleft in the rock about 3 inches wide and at least an arm plus crowbar length. Stacking space is starting to be a premium but it looks like this is the only sensible option we have for going forward. It may be worth squirreling up into the inlet at the bottom of the dig (behind you) to see if this offers a bypass.

Back on the surface we were met by Starfish and Duncan who had found a sizeable stream about 50m south of the dig which sunk when it reached the limestone boundary. It had now been dark for an hour or so and the temperature had dropped dramatically so we called it a day and departed for the Lamb and Fox which was now open. Chris kept the drill so that he can return later this week maybe and drill and bang the end.

Sunday saw the rest of us return up the hill with a cut back plan. Duncan and I were to scaffold the entrance slope while the other wanted to look at the stream which had been found the night before.

So how do you use scaffolding to shore up a pile of vertically stacked small rounded cobbles? Duncan and I cleared up the top shoring and set to the real job. After inserting a few poles to act as a frame we quickly realised that we had a flaw in our plans. Scaffolding alone is not the answer here. We need some additional technology. On Friday I’d met with the Manager of Big Pit and worked an agreement to take advantage of their huge shoring store. Much of what is up there is massive and is of no use to us. However they do have some heavy weight wriggly tin which interlocks and sheets of thick wire mesh. This could form the back of a scaffold cage. Or Duncan has suggested using Portland cement in sandbags. We’d welcome any comments or other suggestions as we were stumped as to how to proceed. (A JCB and a stack of concrete rings would work…)

Leaving Cwmwl Ddu, we went to look at the stream sink. This is a pretty impressive find with a much larger stream than goes down CD sinking where it meets the limestone. Following the top of the old mans workings for about 50m along from CD towards the towers it is easy to spot. Pete, Fleur and John had cleared out a hole roughly a meter deep to see if it was worth pursuing but must have been hampered by dry gear. With the benefit of caving suits and having had a soaking in CD we set to enlarging the site. One side is pretty much solid rock so we set to enlarging the pot in the other direction. Stripping off the soil for a yard or so revealed some fairly large boulders. We managed to shift a number of the smaller ones and one pretty big one but where stopped by the remaining ones. This is definitely worth putting some time into to see what happens next…but we need to dispatch the offending boulders on the surface before we can work in the sink proper. I don’t know if you can drill and wack millstone or whether Chris could do the honours for us. Jake is looking to come over on the next weekend session and is also a man of means!

An interesting point about this sink was that although the boulders were covered in soil as you go deeper there is nothing between them. This might mean nothing but I thought that maybe it was because the water had washed it all out before sinking when the place is in spate. While we were there there was no sign of the water backing up and a scaffold bar poked into the hole disappeared for about 3 feet.

Next weekend trip

The every other weekend rota means that the weekend of 26th/27th November is on the cards. Tasks are:

  • Fix the entrance shoring
  • Push the end. We need to dig down in the floor to see if there is a lower way on or just bang our way though or look at the inlet for a bypass.
  • Look at the stream sink.

Planning on coming?

Drop me a line if you think you might be coming so I can get an idea of numbers and what we can achieve.

Henry