This summer, Brighton and Hove is going to change. On 11 June, 17 huge pieces of rolled steel, the i360 tower cans, are due to arrive by barge onto the beach alongside the West Pier. But first things first. We need to get ready…
Preparing the arches
Now that we have been granted listed building consent to rebuild the heavily corroded, structurally dilapidated arches behind our site, work has begun to turn them into part of our beach building.
We have moved the hoarding line on the upper promenade as a temporary measure. For a short while cyclists and pedestrians need to share the pathway. This works well on the beach footpath before 11am, when cyclists are allowed to use the lower promenade as long as everybody is mindful of other path users. Hopefully the same attention will be paid on the upper promenade but please do take care.
Preparing the basement
Those of you that have strolled along the beach footpath or cycled down the promenade, will have noticed the physical change in our site. It appears to be taking on a shape.
At the start of February we began to form the piles, the concrete ‘stilts’ that form the deep foundations of our building. Some of these piles interlock to form the basement wall. During March we put the capping beam on top – this is a solid layer that sits above the piles and transfers the load more evenly. The shape you can now see is the top of our basement.
We have the layout, now we need the depth. The dig is done in two stages. The first, which we are undertaking now, goes down to 1.5m. We need to add temporary props to the structure at this point, which will stop the walls caving in as we dig.
To help us fit the props, we are using an 80 tonne crawler crane. Although it has only just arrived on site, the Hitachi SCX8000 is already playing a major role on site – shifting all the heavy kit that we will need to create the basement. The shiny red crane is also providing construction and environmental enthusiasts the chance to see a new breed of crane in action. The Hitachi SCX8000 has a high performance exhaust filter, cleaning the air using anti-pollution technology. When tests were done in London, the air that came out of the exhaust was cleaner than the air the people of the city was breathing.
At the end of the month we will start to dig down to the bottom. Digging 8.5m down into chalk on the seafront is no easy feat. We go below the tidal water level and so the engineer’s first challenge was to find a way to make the working area dry. Our plan is to drill down 16m and put ‘well point pumps’ in. These pumps allow us to remove all the water and keep the area dry while we work. Once we pour concrete in, the ground is effectively ‘plugged’ and we can remove the pumps.
With the water removed, we need to be able to shift the huge amount of shingle out of the basement. This is the second part of our big dig and a long reach excavator will be arriving on-site imminently. This highly specialised piece of kit can reach out 16m and will allow us to remove all the shingle from the basement. The crawler crane will support the work, enabling us to lift things in and out of the newly formed space.
As we dig, a steel cage is built within the basement. The rods are arriving on-site as individual pieces at the moment, but will be carefully linked together to form a mesh like structure to fit – much like they were for the helical cages used within the piles. The rods further strengthen the concrete when it is poured in at the end of May.
Preparing the beach
So where will the shingle from the basement go? Ever keen to reduce the need for landfill, we are reusing the shingle to create a ‘beach mat’ across the other side of the footpath from our site. We need to reinforce the beach as this is where the 100m crane that builds the tower will sit. We will also store our 17 cans in this area, ready to be lifted over the path and positioned one-by-one.
To get the shingle onto the site we are using a vacuum excavator truck. The truck will sit on a platform on the beach, attached to a pipe that runs under the footpath and on to our existing site. The shingle is deposited into the pipe and will literally be sucked through to the other side. A dumper truck on the beach will collect the shingle and deliver it across the beach, helping us create a flat platform.
To protect the existing beach, a geo-textile membrane is laid over the beach before we deposit any shingle on top.
Anyone who has ever walked down a shingle beach will know how the ground can give way beneath you on the steep slopes. To prevent this, gabions will shore the beach up at the far end of our platform. We will then add another layer of geo-textile membrane across the whole space so that we can deposit the layer of sand and stone needed to support timber mats.
There is still lots to do before June, but with the fences going up this week it is easier to get an idea of the working area. In the next few weeks we will be giving an update on how the beach landings will work and how we are going to celebrate the arrival of our space-age cans. Summer is going to be busy, so watch this space.