Hello, up there

Above ground, there's some impressive machinery in use as well. This is nowhere more evident than in constructing the 15 viaducts that carry the tracks over rivers, valleys and roads. In all, viaducts take up 10.5km of the route.

On a site visit to the viaduct over Allandale Road in Midrand, one of the operation's two launching girders (Hakuna and Matata) could be seen in action. Effectively cranes, these huge machines are "driven" on rollers across supporting pillars to assemble gigantic precast segments.

After being placed in position, the segments are glued with epoxy and stressed by means of high-capacity jacks tightening cables drawn through internal "tendons" to form the railway deck spans.

Although underslung launching cranes are used extensively in other parts of the world, this is the first time they have been used in Africa. Not only is the method swift, it also allows work to proceed without disrupting traffic underneath.

To give some idea of the massive scale of the operation, consider that each segment can weigh about 50 tons; an entire span weighs up to 1100 tons. Viaducts are cast in sections of about 2.5m (individually designed according to its position and required angle). The longest viaduct on the Gautrain route will span 650 metres.

Deck segments are cast at the company's precast yard, said to be the largest in Africa. Its twin concrete batching plants churn out a variety of concrete items including viaduct segments, bridge beams and parapets at the rate of 120m3 of concrete an hour.

When work is complete, the yard will be demolished to become the depot for Gautrain's 24 train sets and 150 buses.

Work in progress

Construction work on Gautrain is approaching the two-year mark. It's due to be completed in two phases, running more or less parallel.

Phase One lasts 45 months and includes the network between OR Tambo airport and Sandton, together with the depot and operations control centre near Allandale Road in Midrand.

Phase Two lasts 54 months. It covers the rest of the rail network, including stations linking Sandton to Johannesburg's Park station, and the Midrand-Hatfield (Pretoria) route.

During year one, most of the attention was on the depot and the southern section of the route between Park Station and the OR Tambo airport. This year, construction of the northern section will be ramped up.

One of the highlights will be the meeting of two tunnels being excavated from Marlboro Portal and Mushroom Farm Park.

With the civil engineering work well under way, the first 500 tons of specialised hardened high-speed rails have already arrived from France and were due to be laid near the Midrand depot. Over the course of the next year and a half, another 185 000 tons of rails will follow.

Rolling stock testing will be completed in the UK before the end of 2008, and the first shipment of rolling stock components will arrive to be assembled at Union Carriage and Wagon in Nigel.

It's clear that Gautrain will be making an enormous impact — economic, social, and environmental. The construction process is certainly not exempt from that. For instance, it's one thing to dig tunnels; but what to do with the excavated material?

As we watched at Gautrain's Linbro Park crushing plant, the material arrived in a constant stream of trucks. There it was prepared for use as fill, in areas such as embankments.

As for the leftover material — there will be plenty of it — some ideas are being mooted. It's possible that what Imbokodo spits out today will be used to fill in the existing environmental scars of old quarries and erosion dongas.