This public engagement event at the Baptist church in Lochgilphead Tuesday March 19 must have been very poorly advertised.
None of my wide circle of acquaintances was aware of it.
During the 30 minutes or so I spent there, there were less than dozen or so members of the public present – certainly no queue to gain access!
The exhibition was excellent: an Interim Solution involving the Old Military Road and a Long Term Solution were described.
As I understand it the main purpose of the Long Term Solution could be defined as ensuring that the debris from the largest credible landslip event during the period of say, 10-50 years hence, would not result in traffic disruption. Climate change indicates the possibility of increased scale of landslips as time goes on.
It is unclear whether the LTS addresses the safety problems of the present arrangement, i.e. closing the road whenever there’s a forecast of heavy rain. And if so, how?
A few moments though tells us that there are basically two ways of achieving the main purpose of the project: by ensuring that all of the landslip debris either: (A) passes over the carriageway, or (B) underneath the carriageway.
To achieve (A) the carriageway needs to be moved into the ascending slope of the hillside, i.e. tending towards a tunnel or partial tunnel. Unfortunately the vast amount of hillside removed during this work makes it very difficult at this stage to go for a partial tunnel, ( i.e. to construct an arrangement whereby landslip debris would pass over the existing carriageway.) In fact a straightforward tunnel seems to be the only realistic way of achieving option (A).
To achieve (B) the carriageway would require raising above the highest level of falling debris, i.e. tending towards bridging the debris flow (by virtually creating a sloping viaduct across the face of the hillside). It is essential that the carriageway support structure does not interrupt the flow of debris down into the valley. It is unclear how to achieve this.
All the work carried out so far over the previous 10-15 years (at a cost said to be over £80million) has attempted to begin a type (B) solution, and the LTS appears to be an extension of this scheme. I fear one would have great difficulty in persuading a civil engineer to build a sloping viaduct across the face of a hillside which itself is subject to landslides. The danger of the supporting towers suffering damage from the debris flow leading to collapse would be too great.
Motoring around the hilliest parts of Europe, where there are many tunnels and partial tunnels (one side partly open to the view in places) one is very unlikely to see anything resembling the proposed LTS – the flat-roofed debris shelter would allow boulders to pile up on it and possibly cause the roof to collapse.
Any roof should have a downhill slope to allow debris to slide into the valley. It is unclear how to achieve debris removal from the catchpits or screens without causing traffic disruption.
The presentation video needs to be extended; it’s all very well showing traffic proceeding along a new carriageway. There is a need to demonstrate just how it would operate in the event of the maximum credible landslide.
The logical answer to the situation is to admit that the safety problems with the proposed LTS scheme may be too great to overcome without substantial (and costly) changes – so why not just bite the bullet and go for a tunnel solution?
It would probably work out cheaper, quicker and certainly more effective in meeting the project requirement.
There would be no need for an interim solution involving the Old Military Road, no need to empty catchpits and screens and no need to close the road whenever heavy rain is forecast.
John Dyment, Lochgilphead
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