Mott MacDonald and VolkerFitzpatrick faced the task of revamping a busy station to reflect east London’s chemical history – while also keeping to extremely tight timescales. Lucy Alderson takes a look.
Throughout the 19th century, Hackney Wick developed a name for itself as one of east London’s key industrial hubs.
By 1870, it was home to 10 chemical and manufacturing centres. The latest concoctions and products would be loaded up on freight trains, carrying these goods along the Hackney rail line to the rest of the UK and beyond.
Nearly 150 years later, the now redundant industrial landscape of Hackney Wick has attracted London’s tech start-ups and creative scene.
Money is being pumped into regenerating the area, which is just a stone’s throw away from the Olympic Park.
As part of the area’s continued renaissance, in 2014 Mott MacDonald was asked to look at options for a revamp of Hackney Wick Overground station.
Reflections of past and present
The brief was to create a station that reflected the area’s past and present, and Mott MacDonald alongside principal contractor VolkerFitzpatrick started work on the revamp in 2016.
One critical element of the project was the creation of a subway underneath the tracks – with just a matter of days to deliver this part of the work.
The team was granted permission to close the tracks for four days in April 2017 to complete this task. With only 99 hours to create a subway shaft and finish off construction of the station platforms, work was planned meticulously to the hour.
It was vital that the team handed the railway line back to Network Rail on time; failure to do so could have meant a further two-year wait for the team to receive permission to close the tracks again.
“It’s an unusual design as you have a large concrete roof slab supported by one corner on a concrete core”
Nick Ling, Mott MacDonald
Around 18 hours was spent excavating to make way for the concrete subway portal to be slotted into place. Operatives removed around 4,500 cu m of material, with 8 cu m of material taken away every two minutes during this period. Catenary scaffolding was used to lift and hold the signal cables in place while the portal was manoeuvred in place.
“There was a sigh of relief when we finished the four-day blockade,” says Mott MacDonald project manager Sarah McCarthy. After 99 hours and with 4,500 cu m of material excavated, the station subway was completed and construction of the station building could now begin.
Blade column challenge
One of the most technically challenging aspects faced was the construction of the ‘floating’ roof slab, according to Mott’s technical director Nick Ling.
“It’s an unusual design as you have a large concrete roof slab supported by one corner on a concrete core (the lift shaft),” he says. “At the other end, it is balanced on top of a relatively slender concrete column.”
Supporting this element, which team referred to as the “blade column”, is a secant piled wall that was built to support the embankment. This allowed the 10 m-high blade column to be supported by four of these piles.
Next up was the lift shaft that acts as a second supporting column for the floating roof slab. The operatives then built temporary works to support the load of the roof while it was under construction.
Some 50 aluminium columns served as props for a timber frame, which acted as a mould for the concrete as it was poured into the roof.
“We went into a lot of detail as to how to de-prop the roof. As you take these props out, the concrete structure deflects”
Nick Ling, Mott MacDonald
The roof contains an intricate web of reinforced steel supporting beams to account for any other loads such as wind and snow.
With concrete poured to form a 250 mm-thick slab, the team had to wait 28 days before it could begin removing the temporary works, leaving the roof balancing on the blade beam and lift shaft.
“We went into a lot of detail as to how to de-prop the roof,” Mr Ling says. “As you take these props out, the concrete structure deflects. You have to be careful about the sequence in which you take [them] out […] to avoid overstressing the structure or the props.”
Its complex nature meant it took the team two days to dismantle the temporary works.
Alongside the intricate engineering, several stand-out design features have been included in the new-look station to celebrate Hackney Wick’s history.
The area was renowned for chemical manufacturing during the 19th century, and this is reflected in a mural fitted into the station entrance, with chemical symbols lining the bottom of the staircase.
As well as reflecting the past, Mott MacDonald and VolkerFitzpatrick also had to make sure the station could potentially accommodate a six-storey building on top of it at some point down the line. While the team’s revamp was completed in May, it is not yet known whether these plans for further development will come to fruition.
Although Hackney Wick’s chemical manufacturing past is a distant memory, the team hopes the finishing design touches to its station revamp will mean they will not be forgotten.