​Not just buildings

Infrastructure

Access to, from and around a logistics site is just as important as the distribution centres. The extent of the infrastructure works needed at each of our parks varies. But when we built the Sainsbury’s distribution hub at Prologis RFI DIRFT, we faced a particularly complex challenge.

Not just buildings


When we agreed with Sainsbury’s that we would deliver a 1 million square foot distribution hub, we also agreed that the building would be rail-connected with its own intermodal facility. To do this, we had to extend the existing freight line that comes through DIRFT - linking the development to the Northampton loop of the West Coast Main Line – and take it over the A428 to a railhead beside the new distribution centre.

Visitors are surprised that the new railway line lies on a 9 metre high embankment.

Mark Shepherd, Prologis

Why so High?

When visitors first come to the DIRFT site, they are surprised that the new railway line has been built on a 9 metre high embankment since the surrounding land is relatively flat. But the embankment is essential because the rail track has to cross the A428 on a bridge that is sufficiently high for large vehicles to pass underneath. The same line will also serve the third phase of Prologis RFI DIRFT, which means that it will need to cross another bridge over the A5 to reach the new site.

The embankment, which runs for 800 metres along the western boundary of the DIRFT site, will also support Sainsbury’s intermodal facility – a 400 metres long by 30 metres wide concrete slab where goods will be unloaded either directly onto trucks or into the warehouse for storage. It will also act as an environmental bund, providing an acoustic and visual barrier between the distribution hub and future residential development.

Because the embankment will carry the railway line to the new phase of DIRFT, it has been designed to carry four lines of track; two will stop at the Sainsbury’s depot, while the other two will carry on through the site, over the A5.
 

Meeting the Challenge

When we started to design the embankment, we realised that we did not have enough room on the site to build a freestanding structure with battered slopes. Instead, we could see that we would need to build retaining walls to support the structure. The situation was complex and it took about eight months of working closely with Volkerfitzpatrick, the main contractor and with the supply chain before we could finalise the embankment design.

Examining the different options, it became clear that the most effective solution would be to divide the embankment into sections and to build the steeper slopes with earth reinforced by layers of geotextile.

To give the slopes facing the Sainsbury’s facility an attractive stone finish, we have covered the structure with a steel mesh structure, lined with a geosynthetic layer and filled with crushed concrete from the site. On the opposite side of the embankment, the geotextile layers include topsoil, which will be seeded with a wildflower mix designed to attract bees as part of the site’s landscaping.

The design and construction of the DIRFT embankment was complicated, but it is now complete and the Sainsbury’s distribution hub is working well. Looking ahead, we are now in an excellent position to take the railway connection into the next phase of the development.