The twenty-sixth event in a series of monthly events taking place in different squares of the Dartmoor 365; the square the event is chosen at random by raffle at each event. The square pulled out for this month is O2 Grenofen Tunnel. The event will start at around midday at the given co-ordinates for geo-chat, TB exchanging etc. People are free to come and go as they please. Lala and I will be there until around 11am, but depending on the weather/attendees it may go on for longer. We may even find ourselves in the Cafe afterwards!
Authorised by an Act of Parliament on 24th July 1854, Brunel's broad gauge South Devon & Tavistock Railway was constructed in the late 1850s, opening to traffic on 21st June 1859. It was converted to standard gauge in May 1892 but the rails became redundant on 29th December 1962 when they succumbed to closure, snowfall curtailing the service and the planned commemorations.
The route was heavily engineered, featuring six large timber viaducts (which were replaced between 1893-1910) and three tunnels. The most northerly of these escorted the line under the west side of Grenofen, through a 374-yard bore measuring 18 feet wide and 22 feet high - generous proportions for a single track, albeit originally broad gauge. This section of line reached its summit close to the tunnel's midpoint. Though straight in plan, the track encountered a curve to the west through both approach cuttings. The imposing portals are stone-built, boasting a string course and unusual voussoirs. The tunnel has a horseshoe profile and is masonry-lined throughout. Some of the refuges are backed with brick. Water ingress is considerable in places.
Structure number LAN/10m 62ch, the tunnel was looked after by British Railways Board (Residuary) for many years until being acquired by Devon County Council, at a cost of £1, for incorporation into the Drake's Trail cycle path. Funding for the scheme came from the council, together with the European Union and the South West Regional Development Agency. Put out to tender in April 2011, the works included laying a 3m-wide running surface, pointing, drainage, repairs to the refuges, stitching works to the portal and the erection of steel canopies in areas of severe water ingress. The installation of lighting involved drilling a 17m bore hole from the road above the tunnel as a means of introducing the electricity supply. Bat mitigation works were also undertaken. The tunnel's footpath was officially opened on 5th September 2012.