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 River Alyn Sink Holes - New Caves ?

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Ian
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PostSubject: River Alyn Sink Holes - New Caves ?   Fri 05 Jun 2009, 1:43 pm

On Thursday the 4th June last, myself, Andy & Jo took a wander along the River Alyn to investigate the various sink holes whilst the water levels were so low.

Taking a bearing from the Cilcain Bridge, we know the furthest sink is “Dead Duck Cave” which is close to the sewage pipe beyond the caravan site on the way to Poachers cave. I understand (please correct me if I am wrong) that this sink becomes the waterfall in the lower series of Poachers cave.

Coming back towards the caravan park, there are three sinks in the river bed all within a foot or so of each other (the same sink then) which catch the water when the flow is not strong enough to pass across to dead duck cave. These sinks are virtually at the edge of the caravan site. This sink was, however dry. Let’s call this “Caravan Edge Sink” for now.

Walking further back towards the Cilcain bridge (another 50 feet), in the centre of the river bed, is a rather obvious and quite large (10 inch diameter?) sink hole which I have not seen before as water has always flowed over it when I have been wandering around there (on this occasion the water was not reaching it). Let’s call this “Centre Hole Sink” for now.

Walking further back to the bridge again, this time about 200 feet (and within, say, 200 feet of the Cilcain Bridge) there is another sink on the opposite bank to the caravan site. This sink was taking water even in the driest of weather. The aperture was around 12 inches and it seemed to run under soil rather than down through rock although it must, of course, be going through the limestone bed. Let’s call this “Far Bank Sink” for now.

Walking further towards the bridge and actually arriving at the bridge we find the deep pool of water which reaches some distance on both sides of the bridge. Here, on the bank of the caravan site, is a significant sink which appears to be taking the majority of the water in drier weather from the Coed Nant Gain Rising – so much so, there is a small whirlpool or eddy visible with a wonderful “gurgling” sound and tumbling of water behind the rock. Let’s call this “Bridge Sink” for now.

So, we have a number of sinks …..

Dead Duck Cave
Caravan Edge Sink
Centre Hole Sink
Far Bank Sink
Bridge Sink

The question is this …. Where does the water go from all these sinks ?

(Yes, I know it all ends up in the Milwr tunnel)

Assuming it drops into Poachers …. Where in Poachers does it manifest ?

There is a video of it here ….

http://www.youtube.com/watch?v=tXnwMBc7BSw

Is there a piece of cave we are missing ?

Shocked

Ian

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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Fri 05 Jun 2009, 3:39 pm

I was under the assumption that the water from the River Alyn did drain to poachers? I know that from the terminal chamber in poachers there is a flow of water coming from the direction on the River Alyn. However the celing is too low to follow in the direction of the entering water.

I can't think of any other caves in the area where it may be going to, Poachers is the closest to the sink holes.

Anyone else have any ideas?
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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 2:25 am

Sub, there is no doubt that the water in Poachers is coming from the River Alyn but it is not certain that all the water from the River Alyn is going into Poachers (if you see what I mean) and there are some anomalies highlighted by the sinks.

Additionally, there will be more sinks that are not evident .....

At the terminal chamber where the water enters, the water is coming from somewhere well beyond the car park (and caravan site) and is probably coming from close to the Coed Nant Gain rising (a logical assumption as water cannot flow upwards).

Walking from the terminal chamber back towards the entrance you pass a convergence of water in two places but in both instances the water is coming from your right (as you walk back) and since Poachers does not zig-zag under the river Alyn, this water cannot be coming from the sinks because it is on the wrong side (and with the first convergence it is too far back in any event).

The second convergence is in the main Boss chamber which, due to the height of the chamber MUST be under the hillside and cannot be under the river (and, again, the water converges from the wrong side).

The next appearance of water is where the "Helter Skelter" is located and it is coming into that chamber in two places very close to each other - that is on the CORRECT side and I expect that this water is indeed coming from one or more of the sinks above.

The thing is, the water comes in there even in the absolute driest weather and it could only account for two sinks; so we are still left wondering what is going on.

If nothing else, it is interesting to consider what we are missing Very Happy

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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 3:03 am

I was up at the other end near Loggerheads park last week and noticed a definite sink. There are known to be many up there and the filling in project that went on years ago failed to plug them. Since the 70s many of these have been dug out by cavers with little success and filled back in. There may be a few that do go, but it seems often that the digs end at an impenetrable bit, so if you want to dig then best seek permission first but it may be worth checking if it's been dug there before to save yourself the hassle of finding out the hard way. In addition to the sinks, there is also a dry sink/rift by the side of the Alyn called the 'Tan-y-Graig Rift'. It's on the south side of the Alyn at SJ193633. Years ago they built a wall to stop the water going in but apparently you can crawl in about 6 ft or so and it may not have been dug. The whole gorge must be riddled with holes like a swiss cheese.

marc

(Also, sorry Ian for correcting you, but in the world of caves the water DOES flow upwards as is seen when the springs occur, or spout, when the water table becomes higher that the resurgence and it can actually spurt out. Apparently in times of immense persistent rain the entrance to OHA spurts out of the holes in and around the main entrance)


Last edited by marc on Sat 06 Jun 2009, 3:11 am; edited 1 time in total
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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 3:07 am

I am pretty sure that it is all SSSI land and digging would be forbidden. I would like to have a peep at your "wall" though Very Happy

I'm not suggesting we dig up the River Alyn, just pondering where the water is going as I don't believe it is all going into Poachers and I am considering what else may be down there affraid

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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 3:20 am

Ian wrote:
I am pretty sure that it is all SSSI land

http://www.ccw.gov.uk/interactive-maps/protected-areas-map.aspx

Will allow you to zoom right in on the SSSI and view the boundary's. Needs Flash player.

Interestingly it appears that the river bed from Cilcain Bridge to somewhere downstream (perhaps the far end of the caravan site) is not within the SSSI


Last edited by Les W on Sat 06 Jun 2009, 3:26 am; edited 1 time in total
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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 3:21 am

Is all digging on SSSI forbidden?? Maybe, but with a proper well thought out case put forward perhaps not. I know on Halkyn Mountain SSSI that they crop a lot of the non native vegetation, so managed destruction must be acceptable in some cases. The SSSI is designated for the Alyn Valley Wood and Caves, so you could argue that digging may help the cave aspect of the SSSI and open up some more caves for the academics to investigate.

I think the other area that is really interesting is the VERY large depression/shakehole beyond the far terminal chamber of Poachers. I feel that the cave would previously have gone much further, so a dig beyond could be worth looking at, and it is known that one of the scree banks is actually draughting in several places up that way.
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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 3:53 am

Digging is probably forbidden, but what is forbidden or permitted is in the gift of CCW (and NE in England). When an SSSI is scheduled there will be a list of PDO's (Potentially Damaging Operations) that will be notified to the land owner concerned. These PDO's are not the same for each SSSI as they are all scheduled for different reasons, Biological, Geological, etc. By its very nature digging is destructive and as such is certain to be a PDO, however a lot of the geological (cave) SSSI's on the Mendips have exemptions in the schedule taht generally say "...is not permitted, unless this is the normal practice of cavers" (cavers may have had some (lots) of input at the scheduling stage) Very Happy

It is not impossible to get permission from CCW (and NE) to carry out certain PDO's, but you will need to put together a well thought through proposal that will include things like risk assessments and safety issues, as well as limiting damage to the site, and will probably include some strict time scales and probably restoration of the site at the end of the project. It will also depend on why it was scheduled in the first place (what it is supposed to be protecting) i.e if it was scheduled because a rare bumblebee lives there then a hole in the corner of the river is not really going to affect a bee, but if it was scheduled to protect a limestone cliff or cave then a quarry is unlikely to be given any consent.

It also will depend on what sort of relationship you have with your local CCW officer as it will ultimately be their decision or recommendation that decides whether you are successful with your application.

Obviously the land owner will have a say in what you do on his land as well but he cannot overule CCW's decisions. CCW have legal status over SSSI's with some very severe punishment for infringements. They are after all charged with protecting the sites.
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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 06 Jun 2009, 8:05 am

Excellent information Les and thanks for the link to the CCW.

We have had some dealings with the CCW but don't know whether or not the river is SSSI (I assumed it was).

I have looked at the CCW website link you provided and confess I can't work out how to determine what is or is not SSSI land on it - I shall have a further play with it Very Happy

..... You seem to be on every caving forum in the land ! What a Face

Regards,

Ian

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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 13 Jun 2009, 2:07 am

Ian wrote:
Excellent information Les and thanks for the link to the CCW.

We have had some dealings with the CCW but don't know whether or not the river is SSSI (I assumed it was).

I have looked at the CCW website link you provided and confess I can't work out how to determine what is or is not SSSI land on it - I shall have a further play with it Very Happy

If you zoom in and look at the red shaded area (SSSI's - look at the key) you will be able to zoom to a level where you can determine the boundary with some degree of accuracy. It looks to me that the edge of the SSSI follows the road, crosses the bridge and then detours around the carpark. it then seems to cross the road and follow the boundary of the caravan site and then cross back over the river to include the fields and woodland to the north.

It is almost certain that the SSSI boundary will follow physical features such as road edges and field boundaries as the scheduling is a legal process that will require precise delineation of the area (if somebody is in court for transgressing then the legal system will require accuracy in determining guilt ("was the accused within the SSSI?" "I'm not certain m'lud, the boundary is a bit vague at that point" "Case dismissed")

Scheduling is to protect a site from PDO's and as such NE and CCW don't schedule gardens or areas that are already damaged (buildings, active quarries, etc). If you look you will see that the sewerage works is exempted from the scheduling, as is the caravan site. It appears to me that the river bed along side the caravan site is also outside the area.

To be absolutely certain you will need to consult the definitive maps from when the area was scheduled, your local CCW officer should be able to help you, they are after all employed by you (assuming you are a tax payer Very Happy )

Ian wrote:

..... You seem to be on every caving forum in the land !

Regards,

Ian
Very Happy

I get about Smile
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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sat 13 Jun 2009, 2:51 pm

Screen shot of zoomed in map of the Alyn Woods SSSI. You can see how the boundary skirts around the car park

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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sun 14 Jun 2009, 2:42 am

Les,

Thanks a million for this cheers

ALL of the sink holes are in the white section of the river which I guess means it is ok to flick the odd pebble around in there.

"Dead Duck Cave" which is, itself, a sinkhole is just a little further on along the river and is in the red SSSI bit.

I wish I could get my head around websites better as I could not figure out how to do that .... you're a star !

Thanks Very Happy Very Happy Very Happy

Ian

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PostSubject: Re: River Alyn Sink Holes - New Caves ?   Sun 14 Jun 2009, 5:01 am

Ian wrote:
Les,

Thanks a million for this cheers

ALL of the sink holes are in the white section of the river which I guess means it is ok to flick the odd pebble around in there.

Whilst it is probably ok you need to be sure that it is outside the SSSI, also, if you find anything it will almost certainly end up within the SSSI (unless it goes straight down Very Happy ) This is probably not a problem but you may want to consider the implications if it is a geological SSSI (although people are digging in other caves under the SSSI, but perhaps this is not a problem because the powers that be cannot see it Wink ).

Ian wrote:

"Dead Duck Cave" which is, itself, a sinkhole is just a little further on along the river and is in the red SSSI bit.

Ian


I think you ought to speak to your local CCW person about this site if you want to dig it. They may be quite open to the idea and if the site is in the river bed, then it is quite a dynamic environment and anything you might do will revert to nature quite quickly once left alone.
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