Saturday, 4 August 2012

Grenofen Tunnel

Recently I took the opportunity to go and see for myself what progress has been made with the cycle path through Grenofen tunnel, which will be the new route for NCN 27. To complete the path from Gem Bridge to Tavistock, a few things still needed doing:

1) The path from near the end of the board-walk on the Tavistock side of Gem Bridge to the tunnel itself needed clearing up, and surfacing. Having said that, the last time I went past there it was mostly an enormous mud bath, and has already been improved enormously.
2) The path through the tunnel itself needs proper surfacing. It has been improved to the point that cars can drive through, which wasn't previously possible.
3) Ashmill bridge still isn't a bridge as such. However, much concrete has been poured and I would guess it isn't very long at all before the bridge surface will be in place.

Obviously, as with the work at Gem Bridge, proper surfacing of the path would be the last step of the process, as there is no point in surfacing it while heavy vehicles still need to drive over it.

Ashmill bridge consists of parts that have listed building status, and so construction has to work around the limitations that puts in place.

On the Plymouth side of Grenofen tunnel they are building an interesting side wall to the path. Essentially, it consists of steel latticing bent into a U shape, wider at the bottom than the top, and obviously with a flat bottom. These are anchored to the ground, before the sides are covered in a hessian-like material, leaving the top open. Finally, they fill it with earth, resulting in a strong wall that in time will be overgrown with vegetation.

Overall, I get the impression that the builders are on track to complete this part of NCN27 by the end of September. Once opened, it completely bypasses one of the worst sections along the entire NCN27 and will offer a far better alternative. But whatever you do, be sure to wear a rain coat when cycling through the tunnel as it rains inside, whatever the weather outside!


Ashmill bridge thankfully isn't exactly an engineering challenge,
due to it being quite small.

This photo shows the concrete that has been poured to raise the
bridge surface
This is what the path on the Plymouth side looked like
not very long ago. Now it looks mostly like the
photo to the left, showing the Tavistock side
Approaching Grenofen tunnel from the Tavistock side