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Report - Sapperton Canal Tunnel, Gloucestershire - PART 2 (Coates Portal); March 2015

Discussion in 'Underground Sites' started by Bertie Bollockbrains, Mar 6, 2015.

  1. Bertie Bollockbrains

    Bertie Bollockbrains 28DL Regular User
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    Before reading this you should read Part 1 which is the other portal to this tunnel, for that is where I placed the history for this tunnel and explains why I resorted to snorkeling this tunnel alone and in this bloody weather at this time of year - which I have to admit is not really a clever thing to do. If the thought of snorkeling a mile into a disused canal tunnel in the first week of March alarms anyone, can I just say that I am very experienced scuba diver with plenty of cold water experience. I have also recently returned from Mexico where I cave dived to depths of nearly 70m and up to 2km inside cave systems - considerably more risky than this. By my standards, this water adventure was tame. This explore was done with ground support, careful planning and the appropriate equipment. In the end it was bad air in the tunnel (specifically CO2 build-up) that forced me to retreat, something I was aware in advance could have been a problem. As soon as I recognised the problem I turned back.

    If anyone wishes to follow, let me warn you that once you are pass the roof-fall at chain 74, then there is no ventilation, and being limestone, carbon dioxide gas is excessive.

    THE EXPLORE:

    Was meant to have been a leisurely paddle in a canoe with other members with a few beers, unfortunately that wasn't to be due to access problems. So I went home, had a good think and came back another day with a new plan - which basically was just me all alone and snorkeling in as far as a I could.


    Lets look at some of the equipment used... the silver torch is an 50W Mares underwater torch and one of two used. My normal urban explore torch was used for the roof-falls. The pink float was my means to keep my camera as dry as possible and was towed behind me using the rope. The camera was triple bagged in dry bags and tied onto the float. For obvious reasons there are no photos of the actual snorkel part of this adventure. The photos you will see are mostly from the dry land of the rock-falls at chain 74 and to my furthest point reached at chain 82. There were two points on the return trip where the water was shallow enough for me to risk getting the camera out. For the most part, the water was 1.5 to 1.75m deep, but could well be much less in the summer. This explore took over 4 hours during which time I was constantly wet and an underwater swim is needed to get in. Surprisingly I never got cold thanks to 3 layers of 5mm wetsuit, with neoprene hood, boots and gloves. A climber's helmet was also worn.

    [​IMG]

    There's no photos of the swim in, I was too scared to get the camera out over the water, so the photos are of the return trip and start at the furthest point reached. First photo is at chain 82 (about 1 mile in and just short of the half-way point through the tunnel). The air was foul and that is why I turned around.

    [​IMG]

    From chain 82 to 74, there are constant roof-falls that have to climbed over. It was obvious that there will other roof-falls in the near future.

    [​IMG]

    [​IMG]

    [​IMG]

    Chain Marker marking 76 chains in from the Coates Portal (1 chain is 20.1m)
    [​IMG]

    And still the roof-falls continue..
    [​IMG]

    Once past the first (or final if returning) roof-fall at Chain 74, the portal can be seen over a km in the distance...
    [​IMG]

    After swimming for about 15 minutes, the portal doesn't appear any closer.
    [​IMG]

    Looking into the tunnel...the graffiti says 1014.50m in
    [​IMG]

    Swimming for eternity and still that bloody portal doesnt seem to be any closer
    [​IMG]

    At 950m in, I assume that this is one of the springs that was referred to in the history.
    [​IMG]

    Last photo showing a very long swim to go, the portal still doesn't seem to be any closer.
    [​IMG]

    And there's no more photos, as the water was far too deep from this point on for me to get the camera out. What I will say is, that on exiting the portal, the footpath cannot be seen from the water, and likewise the water cannot be seen from the footpath. On climbing up the short wall that lined the canal,I popped my head up over the parapet looking like some sort of swamp monster emerging from the depths. I was covered in mud and pondweed. The lady that was on the path actually screamed. MWHAHAHAHA (evil laugh).

    What the lady on the footpath saw:
    [​IMG]

    Thanks for looking.
     
    #1 Bertie Bollockbrains, Mar 6, 2015
    Last edited: Mar 7, 2015

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  2. Lenston

    Lenston Bajo Tierra
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    Commitment for sure mate, looks a good explore :)
     
  3. huey

    huey 28DL Regular User
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    Good report shag,great day out. Mate and I are on it and will post up our stuff soon,thanks for organising it and getting it done! Your best stuff so far,I reckon.
     
  4. wellingtonian

    wellingtonian Subterráneo
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    Enjoyed that :thumb
     
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  5. Oxygen Thief

    Oxygen Thief Admin
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    Officially ridiculous. Did you ever consider an inflatable boat?
     
  6. Oxygen Thief

    Oxygen Thief Admin
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    Also, tell us more about the CO2 / limestone thing. The normal school of thought is "non organic = OK".
     
  7. Bertie Bollockbrains

    Bertie Bollockbrains 28DL Regular User
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    An inflatable was considered, but would had to be inflated in-water in deepish water after gaining access. Would still had meant getting wet.

    I'm not a medic and cant claim to be expert on this, but increased CO2 = hypercapnia which leads to increased breathing rates and other signs and symptoms listed as "flushed skin, full pulse, tachypnea, dyspnea, extrasystoles, muscle twitches, hand flaps, reduced neural activity, and possibly a raised blood pressure." Death is possible. Taken from wikipedia - "Hypercapnia is generally caused by hypoventilation, lung disease, or diminished consciousness. It may also be caused by exposure to environments containing abnormally high concentrations of carbon dioxide (usually due to volcanic or geothermal causes), or by rebreathing exhaled carbon dioxide." Might be stating the obvious here, but an acid (and rain is mildly acidic) reacts with any carbonate to generate CO2.

    The local canal trust did a survey of this tunnel in 2008 and reported this as a possible problem. In their published report they said "On this occasion at least, the CO2 levels were within safe limits." But that was 7 years ago. What I did notice is that whilst in the rock-fall area my pulse was racing and my breathing was much faster then expected for the level of exertion I was doing and resting did not help.
     
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  8. WildBoyz

    WildBoyz Is this the future?
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  9. The Amateur Wanderer

    The Amateur Wanderer 28DL Regular User
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    Awesome :thumb
     
  10. KM_Punk

    KM_Punk Muppet
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    Looks a good tunnel :thumb

    That could have been any number of things like the fact you know there's a CO2 issue so you'll be more aware of any symptoms. Also, when on an explore you Adrenaline levels will increase which will affect your pulse, respiration, perspiration and heighten your senses. You can get CO2 readers if it's an issue that concerns you.
     
  11. CureForPain

    CureForPain Definitely not a Cylon
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    The two things that really worry me are water (I never learned to swim) and bad air. Well done on covering both, you're officially nuts.

    Very true, but it sounds like Mr Bollockbrains is no stranger to this sort of thing - after deep cave diving in Mexico, a canal tunnel probably isn't going to get the ole' fight-or-flight going!
     
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  12. Tomw1989

    Tomw1989 28DL Full Member
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    Epic! :thumb:thumb
     
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  13. Garou Garou

    Garou Garou 28DL Regular User
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    I've had these symptoms whilst bailing out a sump in a cave (Swildons). Not sure whether it is a lack of oxygen or too much CO2. Caused by 3 people working hard in a small space with no air movement.
     
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