The Connaught Tunnel section of the new Crossrail project has provided an inspirational career opportunity for the young team of Taylor Woodrow engineers leading construction. Antony Oliver reports.
Last month the Excel exhibition centre in London’s Docklands hosted an international defence and security show which saw a number of rather large warships arrive and moor up in the dock alongside.
The fact that these boats were able to make it to the show, passing through the Connaught swing bridge and into the Royal Docks was in many ways down to the diligence and passion of a small team of young engineers from contractor Taylor Woodrow.
Ten weeks before the event and a few days after the London Boat Show ended, the team, led by production manager and recently chartered civil engineer Nick Sammonds, began work to construct a cofferdam across the dock.
As part of the critical works to enlarge and strengthen the historic 135 year old Connaught Tunnel ready to accept Crossrail trains this effectively blocked entrance into the dock.
“The work required close liaison with many parties including the Royal Docks Management Authority, City Airport, Excel and the hotels in the area,” explains Sammonds.
“We had 10 weeks to work with the water out of the cofferdam. There were multiple quality, cost, time and safety issues to manage, but ultimately we had to hand back the dock in time for the defence show.”
The Connaught Tunnel contract comprises reconstruction of a surface level railway line, cut and cover approach ramps plus the enlargement and lowering of the brick built twin tunnels that pass beneath the dock, all of which has been out of use since 2006.
The original plan was to backfill the 550m long tunnels and stabilise them with foam concrete before a new large bore tunnel was driven. However, subsequent investigations by the contractor revealed that the clearance beneath the dock bed meant a new method was required to manage risks.
“Our survey showed that we had anywhere between 300mm and a negative number as clearance to the water above,” explains Sammonds. “We didn’t really fancy that so set to work on an alternative.”
Sammonds joined Taylor Woodrow for this Crossrail project having started his career with Balfour Beatty. Originally starting as a section manager, he picked up more and more responsibility on the project and, as a designated engineer for many of the junior engineers on the project, ensures that other young engineers are exposed to opportunities to learn.
Our survey showed we had anywhere between 300mm and a negative number as clearance to the water above
Nick Sammonds, Taylor Woodrow
Finding the alternative was very much a team effort across the contractor, subcontrators and client and, after extending the optimised contractor engagement process by six months, the team settled on a plan to install two sheet piled cofferdams, each formed of two rows of sheet pile 6m into the clay bed below and filled in between with gravel, to drain the dock above the tunnel.
Once installed, the tunnel could be exposed and reconstructed in the dry. Steel segments from previous strengthening works were removed and a new reinforced concrete tunnel roof built. This reduced the risk of inundation and saved an estimated £350,000.
Yet while cofferdam installation was critical to the operation, a huge amount of activity was going on inside the tunnel throughout as engineers widened and lowered the invert while also removing the central piers to create a single running tunnel from the original two.
The tunnel’s ultra-robust brick construction meant that extra clearance in the invert could be created by cutting away excess brickwork. However, where this was impossible a new invert and walls were constructed in carefully controlled bays.
Ultimately we had to hand back the dock in time for the defence show
Nick Sammonds, Taylor Woodrow
Successfully completing this tricky job and being able to withdraw the sheet piles and hand back to dock to allow ships to again pass through the Connaught swing bridge in time for the defence show, was, says Sammonds, a mammoth achievement and down to the efforts of a large number of often quite junior engineers.
- Taylor Woodrow is holding its Inspiration Lecture at the ICE on 10 October to demonstrate the value of careers in civil engineering.
Luke Jackson joined Taylor Woodrow at the start of his degree course after being selected by parent firm Vinci as a Quest scholar for the duration of his studies, giving him only financial reward and great experience.
As a result, during his four year MEng civil engineering with architecture course at Southampton University, Jackson has spent each holiday picking up vital career experience at a range of Taylor Woodrow sites including the Heathrow Terminal 4 forecourt extension and refurbishment and, more recently, a similar project at Gatwick South Terminal.
Since graduating in 2012, Jackson has been working at Connaught Tunnel as an assistant site engineer and in this time has gained experience working with subcontractors and also acted as the site engineer for the self-delivered parapet wall at grade works east and west of the tunnel.
“At the start of 2013 I initiated my Training Agreement, targeting ICE chartership,” he says. “As part of this, I am also on the Taylor Woodrow training and graduate rotation programme, which is structured to better prepare myself and ensure that I am exposed to all facets of civil engineering to ensure that I become a well-rounded engineer.”
Having completed a year on site, Jackson will shortly move to an office-based role in Taylor Woodrow’s Watford temporary works department. Further to this he will work in a tendering team, before a further site placement.
After this he will seek to become charted.
Alex Mitchell has been a key site engineer on the Taylor Woodrow team at Connaught Tunnel for the last two years working on the tricky operation to enlarge and lower the invert of the existing 135 year old tunnel.
She has worked closely with in-house teams and with subcontractors as the project rethought its original plans to support the tunnel with foam concrete then re-bore in favour of a new plan to install a cofferdam and reconstruct using cut and cover.
“The key thing that I have learnt on this complicated job is the vital importance of good communication across the whole team, client, main contractor and subcontractors,” she explains.
“I have been given responsibility but I have also had to take responsibility. I have genuinely felt myself learning every day.”
Mitchell started with Taylor Woodrow in 2007 as a sponsored student while studying for an MEng in civil engineering at the University of Leeds.
She started in 2011, post- graduation at Connaught Tunnel and has progressed under the firm’s training programme to be promoted to site engineer earlier this year.
Throughout this time she has been supported by her designated engineer, site production manager Nick Sammonds.
Having completed the bulk of the Connaught Tunnel main works Mitchell has now secured an unusual six month job swap with the Crossrail client team. This is expected to give her more client, contract and commercial experience.
Site engineer Becky King has worked on the Connaught Tunnel project for the last two years and is currently part of the team responsible for constructing the surface rail works south of the River Thames.
She joined Taylor Woodrow nine years ago as a sponsored student at Nottingham University and has been supported throughout her career.
After graduating, King went onto a training agreement directing her towards becoming an ICE member. Throughout this scheme she has been supported by Taylor Woodrow managing director Graham Stanley, her supervising civil engineer whose job she now aspires to.
“I was sponsored through my BEng Civil Engineering degree through the Quest scholarship scheme. This provided financial assistance, and beneficial summer placements in which I could put my degree to practical use,” says King. Having completed this training agreement, King is scheduled to sit an ICE Member Professional Review this autumn.
Omar Elhoucine’s route to the Taylor Woodrow Connaught Tunnel project team was far from normal having started his working life in a range of occupations from leisure centre manager to security manager.
The switch to construction was, he explains, prompted by the desire to do something more practical and fulfilling.
He enrolled on a construction management degree at the University of East London and he subsequently joined Taylor Woodrow in late 2011 on a three month placement, continuing the second year of his studies.
By early 2012 his placement was extended and he was offered a permanent role as a trainee technician on the Connaught project. Elhoucine was promoted to engineering technician a year later having graduated with a first class honours degree. He was then handed further responsibility as a site team leader for work to form a new sump and pump tunnel and drainage shaft.
“Dismantling the old pumphouse brick by brick, deepening the shaft from 18m to 27m and boring a new 600mm tunnel to drain the Connaught Tunnel represents the last 18 months of my life.”