Dry-stone walls - an engineering feat
The dry stone packed retaining walls are remarkable, in one
place on the southern side a stretch of wall extends for
2,4kms. They range in height from 1/2 metre to 13 metres. Laws
of friction and cohesion govern the pressure on retaining
walls. The bed (ledge, base or shelf) measures up to 1 metre
narrowing to 300mm at the top. Selected stone was used and
laid with the grain at right angles to the natural bedding
line. The walls were battered (sloped inward) in a rise of
1:6. To illustrate the scale of the highest sections of the
walls, Boegoekloof measures 13,1 metres vertically and
the second hairpin on the north, 7,3 metres. Pressure on the
roadway through traffic has compacted and secured the walls
and roadway.
The larger stones on the ledge bedding provided good
drainage but further provision was necessary. Bain's
original specifications give "rule of thumb"
measurements and clear instructions as to how many culverts,
side drains etc. there were to be, but it is not stated how he
arrived at these specifications. What is clear is that they
appear adequate, for after more than a century of rain the
walls are essentially still in place and until recently,
suffered little or no damage.
In September 2000, a concerned group of design and
construction professionals from Prince Albert initiated a
crisis meeting with the Provincial and District Roads
Engineers to discuss their difficulties in providing adequate
maintenance of the Pass after bouts of heavy rains over the
previous three years. The meeting resulted in all concerned
walking the Pass to discuss specific problem areas and a folio
of photographs and drawings was handed over. The Pass
underwent specialist maintenance and Prince Alberters were
delighted to see their old friend (declared a National
Monument in its Centenary year 1988) receiving a comprehensive
facelift.
Stone was the building material of choice so along the pass
visitors can see the ruins of stone buildings: an old prison,
toll hut, hotel and other interesting historical sites.
Often covered in snow in winter, the mountains' unique
micro-climate supports fynbos and a rich bird population, in
contrast with the arid zone flora and fauna outside its cool,
shady gorges. Numerous small mice and voles feed on the
vegetations providing food for the birds of prey which include
black eagles. Sure-footed klipspringers are often seen scaling
sheer rock faces and baboons keep watch from craggy perches.
Travel into the pass to reach the road to
"The Hell".
