Just a quick heads up on access. Martin Downing, the Mine Manager working for Wardell Armstrong on belhalf of United Utilities has posted a note about access to Caeau Shaft the downstream section of the Milwr Tunnel from Pen y Bryn Shaft to the portal on the aditnow site. There has been work going on there for some time and this will continue till the end of 2018 and this area is designed as a working mine. Since the publication of the video of the through trip there is concern that people would be encouraged to repeat it - Don't! His message is below:
"As some of you will know, the HSE has the view ?that once a mine, always a mine? and therefore as soon as we start any work on the tunnel, it has to be designated as a working mine. For the duration of the current works, the extent of the ?mine? (as notified to the HSE) extends from Pen y Bryn Shaft to the portal. Prior to starting the works we contacted Grosvenor CC, NWCC and UCET in order to inform them of this and that there should be no caver access downstream of Pen y Bryn Shaft ? this is also as per an agreement with Grosvenor CC. Unfortunately, the posting of the video of the 2016 through trip on UK Caving has rekindled interest, hence this post to clarify matters and provide some further information.
We would therefore re-iterate that, for the duration of the works (until the end of 2018) there should be no access by cavers downstream of Pen y Bryn Shaft. In any event, the portal is located on private property and there is no agreement for cavers to exit the tunnel here. The area is securely fenced and any damage to the fence, gate or locks could be considered as criminal damage.
The potential hazards of entering the tunnel should also not be under-estimated. Water flows in the tunnel average about 1m3/sec and water levels can rise quickly following rainfall. Walking against the flow for any significant distance can then be very arduous, and impossible in some conditions. There are points in the tunnel where falls have occurred, which have the potential for further collapse and other points where the water can back up to the roof. At worst you could find yourself not being able to proceed downstream with retreat being very long and difficult, if not impossible, back upstream.
There has been mention of the high radon levels in the tunnel. Although levels vary significantly due to the effect of weather conditions on the ventilation in the mine, we have measured naturally occurring radon concentrations up to 40,000 Bq/m3. In terms of dose this is equivalent to approximately 1mSv per day spent underground. To put this in context, the average annual radiation dose in the UK is 2.7mSv and the annual dose limit for a radiation worker in the UK is 20mSv. As such, when undertaking inspections or work in the tunnel, we install ventilation fans that dilute the radon in the working area and also put the tunnel under positive pressure in order to reduce the flow of radon from the old workings. A result of this, however, is that radon concentrations further upstream in the tunnel may be increased over ?normal? levels.
The current team have been inspecting and repairing the tunnel since 2010 and so have developed a keen interest in it. We are happy to work with the caving community but it must be appreciated that access to the tunnel must be undertaken responsibly. The repair works are to ensure the stability of the tunnel and the continued free flow of water out of the tunnel. The works are, therefore, of benefit to all and we would therefore ask for you co-operation.
Many thanks
Martin Downing"
Dave
