Civil Engineering November 2022 | Vol 30 No 10

T his project involved the reconstruction of parts of Trunk Road 31 Sections 2 and 3, between Ashton and Montagu in the Western Cape. The primary objective of the project was to reconstruct the roads infrastructure to a higher standard to improve traffic and pedestrian safety, as well as improve flood ca- pacity of bridges and prevent overtopping of the road during floods. The original track hugged the riverbed with eight hazardous drifts, some of heavy sand and others over rough boulder beds. In 1861, Parliament decided that a road should be built through Cogmanskloof, but no money or convict labour was available. Between 1869 and 1872, the first section from Ashton’s side was constructed, and it included the Hodges Bridge. Thomas Bain, the renowned road engineer, took over the construction of the rest of the pass. From 1873 to 1877 the team worked with only 32 men to construct the 5.5 km long pass, including the tunnel which remains part of the route. In 1915, the first bridge was built near Montagu, which was followed by surfacing of the road in 1931. The first Ashton River Bridge was completed in 1936 as a 100 m long, single-lane bridge. By the early 1950s, economic development, traffic growth and vehicle changes had made Bain’s original route unsuitable. This led to a major realignment of the pass through Cogmanskloof, which included two new bridges and the enlargement of the tunnel. The single-lane Ashton River Bridge was also widened to the structure that was replaced with the latest upgrading. The latest project included the following main features: Q Q Upgrading of the environmentally-sensitive Cogmanskloof Pass which included significant ecological and heritage con- straints, requiring extensive mitigation measures Q Q Extensive rock cuttings and material utilisation challenges (blasting, crushing and haulage) for the realignment through narrow gorge which forms the Cogmanskloof Pass Q Q Construction of three new river crossings over the Cogmanskloof River, including the iconic New Ashton Arch Bridge Q Q Upgrade to municipal services infrastructure through the towns of Ashton and Montagu for the Langeberg Municipality Q Q Construction of specially designed natural stone clad retaining walls and other roadside furniture to celebrate the construction methods and engineering achievements of this historic South African road building monument Q Q Preservation of one of the oldest existing road tunnels con- structed in South Africa using primitive blasting methods Q Q Restoration of the historic Hodges Bridge for foot traffic and preservation of historic fabric of the Cogmanskloof Q Q Preservation of the historic Fort Sidney by limiting vibrations from nearby rock blasting activities and other construction work Q Q Reinstatement of a dry-packed-style stone retaining wall to link with remaining original Bain’s Road retaining stone walls Q Q Special attention to preservation and reinstatement of indig- enous vegetation with an extensive restoration component Q Q Installation of Victorian-style road signposts and streetlights in Montagu, to complement the historic buildings along Long Street, of which 13 buildings are proclaimed national monu- ments (now provincial heritage sites). Local manufacturers, with support from overseas specialists, were used to manufacture and supply specialised components SANRAL SA I CE 2022 Nat i onal Awards Category: Techn i cal Excellence FINALIST Technical Excellence category (Sponsored by SKI Civil and Structural Engineers) KEY PLAYERS Client: Western Cape Department Transport & Public Works, Roads Branch Consultant: AECOM SA Contractor: Haw & Inglis Civil Engineering The Rehabilitation of 13.4 km of Trunk Road 31/2 fromAshton to Montagu through Cogmanskloof including the New Ashton Arch Bridge 22 November 2022 Civil Engineering The New Ashton Arch Bridge The upgrade preserved historical aspects of the existing road design