A. C. Allen writes: Chaplow comments in his summary and introduction on previous conventional site investigations. The Report of the Geotechnical Survey commissioned by the Scottish Development Department from Allen, Gordon & Co., Consulting Civil Engineers, in December 1972 was issued in September 1973. It dealt with all geotechnical aspects of the full length of the road improvement in the Pass and in relation to the site investigation it covered all stages from deciding upon what should be undertaken, issuing tender documents, recommending the contractor, supervising the investigation and interpreting the report received. From considering four choices of route through the Pass, the Report recommended the adoption of a dual carriageway in cut and on embankment, which was detailed on an alignment close to one of the four choices. Possibilities of tunnel and elevated roadway solutions had been considered and rejected on account of excessive cost.
The landslide with a recognised poorly-developed surface drainage system, to which Chaplow refers, affects a length of about 60 m in the two-kilometre-long Pass and it was identified as part of a 600 m long transverse feature between the top of the east side of the Pass and the railway at the bottom, which comprised original undisturbed glacial deposits and slipped reconstituted deposits lying in less consolidated form over, and often between, the ridges of the original glacial deposits. With provision of reasonable drainage, it was considered that the feature would not present any great difficulty during construction or significant risk thereafter, which corresponds.
- © The Geological Society 1984