In June 2016 the UK voted to leave the European Union, ensuring that 2017 would be a volatile year for the construction industry
Walker Construction has been in business since 1964 and has weathered many turbulent events in the previous 52 years. Through remaining positive and facing the challenges collaboratively, 2017 will be an exciting time to be operating in the construction and rail industry.
To facilitate the increase in rolling stock and berthing requirements at Clapham depot an additional maintenance pit with lighting, drainage and electrification to road eight within the existing carriage shed was commissioned.
The scope of the work included; the removal of all existing trackside equipment, running rails, fixings and buffer stops. The removal of the existing concrete slabs was a challenge due to the location of the work within a working building, both dust and noise need to be assessed and managed throughout the duration of the project.
To reduce the noise within the building acoustic fencing and tents were utilised when carrying out specific tasks. The concrete slab was cut using an industrial floor saw with a diamond tipped blade and plenty of water for a dust suppressant. The concrete was broken out using a 3t 360 excavator fitted with a hydraulic breaker.
The installation of shuttering, steel reinforcement and concreting was carried out in sections following on from the installation of new sump drainage.
The depot was fully operational during the work and there were no reported disruptions, safety issues or delays to the contract. This also included the deliveries and collections from site were all pre-planned in advance and undertaken outside of the stations peak hours.
Dalston Kingsland station
The existing booking hall at Dalston Kingsland London Overground station was constructed in the 1980s, due to increased usage of the network, the existing booking hall and gate-line was insufficient to handle the passenger flow at peak times and therefore a decision was made to carry out a major alteration and refurbishment to the stations external elevation, booking hall and installation of eight new automatic ticket barriers.
This contract required close collaboration between Walker Construction, The Trevor Patrick Partnership and the Station Manager to agree on a workable phased programme and methodology without disrupting the station or customer’s experience.
Fire rated hoarding was installed to demarcate the working areas from the public areas and to allow the work to be carried out safely and efficiently during normal working hours. The existing partition walls and retail unit walls were dismantled to create a larger open planned booking hall thus creating space for eight new automatic ticket barriers.
The flooring in the booking hall, ticket office and retail unit was replaced with large non-slip floor tiles achieving a level threshold throughout to comply with specification and regulation. All work that would raise the decibel levels above the legal requirement was deferred to out of hours working with the additional aid of acoustic fencing and tents and the use of a dust suppressant and air extraction units.
Large wall tiles were installed to all the perimeter walls, bonded over the existing tiles to achieve value engineering on the removal of existing tiles. The ceiling was created using a suspended tubular ceiling system with bespoke lighting set within the ceiling.
To compensate for the level flooring the existing door frames were all adjusted to suit and the existing doors rehung and decorated along with the existing door frames and walls. The mechanical and electrical services were replaced throughout as part of the refurbishment including CCTV, TVM and CIS screens, lighting and air conditioning.
The new entrance compensated for the additional flow of customer’s especially at peak hours and with the introduction of additional glazing increased the natural lighting within the booking hall.
Walker Construction was awarded the contract by Transport for London to undertake remedial and strengthening work to an existing retaining wall, located on the East London Line between Whitechapel and Shoreditch High Street Stations. This section of railway, dating back to the Victorian era, is on the northern approach to Brunel’s Thames Tunnel and located eight metres below existing ground level in an open cutting.
The parapet wall on the retaining wall was originally brickwork but was replaced by blockwork due to WW2 bomb damage, and was now in need of replacing. The land to the rear comprised of a residential development with terraced properties in Trahorn Close having gardens that abut to the railway property.
Dense overgrowth had blocked any access to the wall for many years and the routes were also causing issues with the retaining and parapet walls. Once a majority of the vegetation had been removed (except for the Japanese Knotweed), access to the rear of the retaining wall was achieved and the work could begin. The structural surveys carried out pre tender indicated that the walls appeared to be in a stable condition, with no major cracks or defects indicating movement or instability.
However in order to ensure that the wall did not move during the work a temporary wall support system was designed, installed and monitored throughout the duration of the work. The work area was limited to a seven metre wide strip adjacent to the rear of the existing wall.
Once work had begun it become apparent that the extent of the Japanese Knotweed contamination was greater than originally anticipated and additional site investigations confirmed that an additional area of 200m2 needed to be excavated to eradicate the Japanese knotweed. Once the structural engineer was able to gain access to the walls a decision was made for them to be removed and replaced with new walls.
Walker Construction and TFL worked together in developing a design for the new scheme with value engineer in the construction to mitigate delay to the project. As the wall would need to be dismantled and rebuilt in its entirety, additional supports and protection was required to the vertical face of the walls to ensure that no spoil could fail the railway line.
This would allow for the work to be carried out during normal working hours and meant the lines could remain open and operational. To commence the dismantling of the wall the company was required to excavate to a depth of three metres and batter back the sides of the excavation.
An eight tonne 360 excavator with zero tail swing and slew restrictors under astute control of the operator, banksman and machine controllers carried out the excavation work. Vehicle stop blocks were in place to ensure that no plant or machines could foul or endanger the railway. The existing walls were carefully dismantled by hand and held breakers due to the risk of excessive vibration levels being transferred on to the existing wall structure.
The debris and spoil generated from this activity was transported by dumper to a stock pile ready removal from site to a licensed waste transfer station for recycling.
Specialist brick layers built the wall to the required line, level and specification over six weeks. This allowed time for the wall to cure and for the backfilling and top soiling to be carried out behind the new parapet and retaining walls.