Name of the Project
N2 Wild Coast Toll Road (N2WCTR) megabridge projects. 

Location
The bridges will be built over the Msikaba and Mtentu river gorges, both near Lusikisiki, in South Africa’s Eastern Cape province.

The Msikaba bridge is located on the N2, which connects the Western Cape, Eastern Cape, KwaZulu-Natal and Mpumalanga provinces, and traverses the cities and major towns of Cape Town, George, Gqeberha (formerly Port Elizabeth), East London, Mthatha, Durban and Ermelo. This includes a new greenfield section of 112 km between Port St Johns and Port Edward, including the two megabridges and several additional major river interchange bridges.

Only the new greenfield section of the project will be tolled. None of the sections between East London and Mthatha or between Mthatha and Ndwalane, near Port St Johns, will be tolled. The public participation process for the tolling of the greenfield section of the road is yet to start.

Project Owner/s
South African National Roads Agency Limited (Sanral).

Project Description
The Msikaba and Mtentu bridges form part of the N2WCTR project.

The 580-m-long Msikaba bridge will be the longest main span bridge in Africa – constructed using the cable-stayed method – and the second-longest main bridge span in Africa after the Maputo-Catembe suspension bridge, in Mozambique. With a deck height of 194 m above the river valley, Msikaba will become the third-highest bridge in Africa and the 133rd-highest in the world. The Msikaba bridge cable-stay design will ensure that the construction of the bridge will have no direct impact on the pristine gorge environment almost 200 m below, which is one of the environmental requirements in building the bridge.

The bridge is being built from the north and south banks of the gorge and comprises two identical halves, each spanning 290 m, which will meet midpoint over the gorge. 

Each half is supported by 17 pairs of cables attached to the inverted Y-shaped pylons, one on each side of the gorge. 

The pylons are back-stayed into the anchor blocks, two on either side of the gorge, by 34 pairs of cables – 17 for each half – positioned 130 m behind each pylon. 

Each anchor block is 49 m long, a width of 10 m at the base (narrowing to 4 m on the spine of the structure), a depth of 17.2 m, and a mass of 21 500 t. 

The 1.13-km-long Mtentu bridge, which includes a 260-m-long main span, will be one of the longest main-span-balanced cantilever bridges in the world. Only ten prestressed concrete girder bridges worldwide have a main span of 260 m or longer. Reaching heights of more than 220 m above the river valley, it will displace the Bloukrans bridge, in the Western Cape, as the highest bridge in Africa and the southern hemisphere. The 141-m-tall Pier No 9 (equivalent to a 40-storey building in height) will also be the tallest bridge pier in Africa and the southern hemisphere.

Being one of the longest main-span-balanced cantilever bridges and one of the highest bridges in the world makes the construction of the Mtentu bridge a technically highly challenging project. The remote location and local social dynamics add to this complexity.

Potential Job Creation
So far, the Msikaba project has created work for 137 unskilled local labourers and 372 jobs for skilled persons, of whom 190 are locals.

Capital Expenditure
The Msikaba bridge project will cost an estimated R1.65-billion and the Mtentu bridge project R3.5-billion.

Planned Start/End Date
The N2WCTR project started construction in 2011. However, the major greenfield portion of the route between Port St Johns and Port Edward started construction only in 2016.

Construction of the Msikaba bridge is expected to be completed at the end of 2024.

Provided that there are no significant delays on the Mtentu bridge project, the construction period is estimated to be 49 months, including a four-month mobilisation period.

Latest Developments
The pylon spires of the Msikaba bridge megaproject are soon to tower almost 130 m high at each side of the 197-m-deep Msikaba river gorge. 

The bifurcated legs of the pylons are being slip-formed, with all the spires extending 95 m from the bifurcation to the top of each pylon, taking the height of the bridge pylons to 128 m. 

Each pylon rests on two inclined legs that meet 21 m from the start of the bifurcation.

At 32 m, the first section of the spire – starting with a diameter of six metres – is uninterrupted for 55.7 m and comprises 14 slipform lifts. 

Then begins the inclusion of 17 anchor inserts over the next 35 m of the spire, which reaches a height of 124 m and will converge to a four-metre diameter. 

These anchor inserts accommodate the 17 cables that run from the anchor blocks, located behind each pylon, to the spire and then down to the 580-m-long bridge deck. 

To accomplish the lifts, a jacking system for the formwork shutters, with eight jacks around the circumference of the spire, is being used.

Each lift is 3.6 m, conducted at intervals of about two weeks per lift, with steady progress being made.

The work is accessed using a specialised stair system, with one set of access stairs from ground level to the top of the bifurcation, and a second stairwell following the shutter system up the spire. 

The formwork system comprises three decks that trail below each other; the interlinked decks lift together as the shutters are jacked up.

“The depth of the gorge means that no work on the bridge deck . . . can be done from ground level,” South African construction  company Concor project director Laurence Savage indicates.

“Everything has to be done suspended from these two pylons – one on the south side of the gorge and one on the north side of the river.”

Like the leg of the bridge pylon, the reinforced concrete spire – with walls 1 m thick – is hollow to reduce weight, and is formed in a tubular design that significantly improves its strength-to-weight ratio. 

The reinforcing bar used in the spire includes 12 mm  to 16 mm bar as lacing, with primary bars of 30 mm and 40 mm used in high densities to carry the significant loads. 

Once the stays and bridge are in place, the load on each pylon will amount to about 7 000 t.

The pylons are well advanced, with about half of the planned concrete volumes already poured by the top of bifurcation. 

After the last anchor insert, a 4 m parapet will be built around the top of the pylon spire. 

Access to the inside of the pylon will be restricted to engineering inspections and maintenance. 

Indicative of the precision engineering being used on the project is the number of activities that must take place concurrently and in a confined area.

“By the time we have completed the fifth anchor insert, for instance, we will have begun the launching of the first deck-segment, followed shortly by the second and third segments. 

“While these activities are taking place, the spire and inserts will continue to be erected and cast,” Savage has explained.

Savage has added that the bridge deck will start launching across the gorge later in the year.

Key Contracts, Suppliers and Consultants
Concor Mota-Engil, a joint venture between Concor Construction and MECSA Construction (Msikaba bridge contract); HVA Joint Venture (Msikaba and Mtentu bridge consultants comprising CH2M and SMEC); V3 Consulting Engineers (lead consultant – Ndwalane to Ntafufu and Kulumbe to Mtamvuna river); ERO Engineers (lead consultant – Ntafufu to Bambisana turn-off); Naidu Consulting (lead consultant – Bambisana turn-off to Lingeni); Aurecon Rohm consortium (lead consultants – Lingeni to Msikaba); Knight Pieésold (lead consultant – Msikaba to Mtentu); and KBK Engineers (lead consultant – Mtentu to Kulumbe).

Contact Details for Project Information
Sanral project manager Craig McLachlan, tel +27 41398 3200 or email MclachlanC@nra.co.za.