Construction World December 2016

Highly Commended

A 3

Civil Engineering and Building Contractors (outside South Africa)

The Senqu River Bridge Project involved the con- struction of a four span, 140-metre-long composite steel and concrete bridge over the Senqu River in the Quthing district of Lesotho, near the town of Mount Moorosi. Two kilometres of approach roads linking the Phamong and Quthing districts were also constructed as part of the project. SENQU RIVER BRIDGE PROJECT

In order to execute the piling and construct the piers, a temporary rock fill causeway was constructed across the river, which allowed the dry season river flow to pass through unabated. Access to the pier foundations for piling and construction equipment was via this causeway. Due to the large seasonal floods which occur in the wet season, it was essential that the pier foundations were constructed during the dry season. The bridge deck consists of three 2 m deep steel girders laced together with cross bracing and a 250 mm thick, 12 m wide in-situ concrete slab cast on top of the beams with in-situ New Jersey parapets constructed on the sides of the deck. Twenty metre sections of the three steel girders were pre- assembled on the launching platform situated behind the eastern abutment and launched in phases across the river. Launching was done with the use of two 150 ton jacks mounted to the east bank abutment with 20 m being jacked out over the river at a time. The composite steel and concrete deck structure in combination with the elongated T section piers set against the back drop of the vast Lesotho mountain range makes for a visually appealing landscape. The 2 km of approach roads have a surfaced width of 9 metres with the layer works generally consisting of a G7 lower and upper subgrade, a cement stabilized G5 subbase and a G2 crushed stone base. The Cape seal surfacing consists of a 13,2 mm aggregate seal and fine slurry. Local labour working on the project were employed from the areas around Mount Moorosi and Phamong. Employees were also educated on life skills, HIV awareness and environmental awareness. Once the project is complete, all employees will be issued with a certificate confirming there involvement in the project and the exposure and training in the above mentioned areas. Some 38 000 shifts have been recorded with no lost time injuries. Given the location of the project and the limited construction knowledge of the local community working on the project, this is a remarkable achievement.

The Phamong district is situated in a very rural, isolated area in the southern regions of Lesotho. For many years the only access for the people of Phamong to the bustling business district of Quthing was to cross the Senqu River by ferry or on foot. When the mighty river is in flood, which can be for up to four or five months of the year, there is little or no access. The building of this facility was therefore essential to give the people of Phamong access to vitally needed goods and services from the Quthing district. The Senqu River at the project’s location is approximately 150 m wide and has a large sand bed up to 25 m deep in some places. When the river is in full flood, up to 2 500 m 3 of water hurtles down between the river banks. For this particular reason, the design of the bridge dictated a solution which required the launching of large steel girder truss sections across the river, followed by the casting of a 250 mm in-situ thick concrete deck with New Jersey parapets. The four spans of the bridge vary in length between 30 m and 40 m. The bridge substructure consists of two abutments situated on the banks of the river and three piers up to 15 m in height situated within the river bed. The substructure is founded on 1 100 mm diameter oscillator piles which vary in depth between 8 m and 22 m which are socketed into the bedrock. The bridge has four spans varying in length between 30 m and 40 m.

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Project information • Company entering: Stefanutti Stocks • Client: Lesotho Roads Directorate • Start date: 20 March 2012 • Project end date: 5 October 2015 • Main contractor: Stefanutti Stocks Lesotho • Consulting engineers: SMEC Consulting Engineers in association with Elite Consulting • Subcontractor: Pennyfarther Engineering • Cost of project: M150-million (Lesotho Maloti)

Construction WORLD

DECEMBER • 2016