Pool Sink is a deservedly popular trip into far Ease Gill. Once the entrance crawl has been negotiated, it is an easy abseil down a set of friendly pitches through a superb stream passage. The route is straightforward, and doesn't require any navigation skills other than being able to follow your nose and the line of eco-bolts. The only useful tip is that the pull-through needs just two 20 metre ropes.
However, the bottom section is not well described in the guide book. Some parts are confusing, and other parts are just plain wrong, and this article is intended to help clarify the area.
The Bottom Pitch Bypass
Northern Caves states: "At the bottom [of the last pitch], a steeply descending streamway with numerous cascades leads to Jacob's Ladder, a spiral climb down which requires care, and after another 2.4m cascade, the passage levels out into Lower 'T' Piece Passage".
This section of passage does not exist. The last (and fourth) pitch is not free-climbable, and this is followed by a short cascade into the lower passages.
Northern Caves also states that "a high level traverse, exposed in places leads down into the stream again thus by-passing the [last] pitch, but this is best avoided."
This is almost true. There is a route which by-passes the last pitch, which can be useful when abseiling through in wet conditions as the pitch can get horribly wet. The route referred to in Northern Caves is as follows. From the bottom of the penultimate pitch, it is possible to climb up the right hand wall of the passage for about 5 metres into a large chamber with an aven off to the right.
The climb up into the high level chamber, however, is steep, off-putting, and objectively dangerous. Fortunately, it can be avoided by a more practical but somewhat more obscure route. Below the penultimate pitch, there are a couple of short cascades. About five metres beyond the second, you'll see a shelf about head height on a buttress formed where a thin inlet enters. Climb onto this, and then step up another metre to a higher ledge close to the roof. From here you can crawl through a reasonably roomy letterbox that leads immediately to the bottom of the shallow shaft mentioned above. One passage leads downstream back into the roof of the stream passage, but another leads upstream to where the floor gives out. From here, an easy climb enters the high level chamber close to the top of the original climb. Heading in a downstream direction leads to an easy traverse round a shallow shaft in the floor, to a point where it is possible to drop a couple of metres into a high-level oxbow. This leads after a few metres to a slither down into another passage, and hence to a climb back into the stream passage arriving at the base of the last pitch. It is this last descent that was called Jacob's Ladder by the original explorers.
In very wet weather, the cascade below the bottom pitch can be bypassed by continuing to traverse downstream for a few metres.
The Borehole Connection
It took me several attempts to find the connection with The Borehole from the bottom of Pool Sink, so I thought it might be useful to clarify this area in case others have similar difficulty. The main problems are that firstly, the passage naming in this area is not particularly intuitive (for valid historical reasons); secondly, the route is a little obscure; and thirdly, Northern Caves is downright misleading. The survey, however, does make sense once you know where you're going and where you've come from.
Green n Smelly Passage is the passage which leads from Holbeck Junction towards Pool Sink. At floor level, however, the main passage becomes Lower T Piece Passage, and Green and Smelly continues as a fairly inconspicuous inlet, which is all rather confusing.
There are two ways of finding the Eccles By-pass connection with The Borehole, and both start at the point where the two routes from Holbeck Junction into Lower T Piece combine in a high chamber with a large fallen boulder almost blocking the exit. The first way follows the floor. Work your way round the boulder into the dry passage beyond, and follow this for 70 metres or so back into the stream to where an inlet enters from the right (true left). This inlet is actually the continuation of Green n Smelly. Follow this to a climb where there is a seemingly unstable chockstone above your head.
You can either climb onto this (it is, in fact, quite safe), or bypass it by crawling through a small hole at floor level on the right into the bottom of a small pit with a rope climb leading to the same place.
Continue for a couple of metres to a hole in the floor where the water emerging from the Green n Smelly choke sinks, and with the entrance to Spiral Staircase Passage, leading up to the Wretched Rabbit entrance rifts, to the right. Clamber into the hole, and enter a smallish passage into which water is sinking. This gets a little bigger fairly quickly, and passes a couple of uninviting junctions, before entering a wide bedding passage with a stream flowing through it. This is the bottom of The Borehole.
The second way joins the first at the seemingly unstable chockstone. On the upstream side of the large block that almost blocks Green n Smelly clamber onto a traverse line about four metres up. Follow this upstream across a widening of the passage, to a junction. Step over the passage at the junction, but continue the traverse along the main passage through a bouldery bit, to the top of the chockstone.
There is also a short but tight connection from Lower T Passage which joins the wide bedding passage directly opposite the Eccles By-Pass point of entry.
The Borehole is a good trip, and a worthwhile alternative to Pool Sink for a pull-through. It is, however, quite awkward and energy consuming, and should not be regarded as a soft option.