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Battersea Power Station Phase 2, London, UK

Located on the south bank of the River Thames in Nine Elms, London and dating back to the 1930s, Battersea Power Station, with its four-chimney layout, is one of the most recognisable landmarks of the capital. A Grade II listed building, Battersea has attracted more than a few popular culture references, which include the cover art of Pink Floyd’s 1977 album ‘Animals’ and was a significant backdrop in the 1965 Beatles’ film, ‘Help!’

Notwithstanding its iconic stature, it has been unfortunate that since the station ceased generating electricity in 1983 the building has remained largely unused, with the condition of the structure being described as “very bad” by English Heritage, which included it in its Heritage at Risk Register. Despite many redevelopment plans, from many different owners, it was not until the site was purchased for £400 million by Malaysian development consortium SP Setia and Sime Darby that plans took shape. Planning consent was granted by Wandsworth Council in 2011 to implement the Rafael Vinoly design. The scheme will restore and inject new life into the Power Station itself, while several new buildings and a new public realm will surround this London icon when all 8 phases are complete in 2025, at which point the development will be served by improved transport links including a new underground station, pedestrian footbridge over the Thames and a Thames River Bus Landing. January 2013 saw the first residential apartments go on sale with construction on Phase 1 commencing 2013.

Battersea PowerStation

Phase 2 of the construction saw over 100,000m2 of office space created from the converted power station. The flexible space is set out across six floors within what was once the Boiler House to create an industrial aesthetic.

BAUER Technologies Limited was awarded the piling works for Phase 2 by Battersea Power Station Development Company (BPSDC) with Mace acting as Construction Manager for BPSDC. Its remit was to design and construct the rotary bored piling and secant walls within the envelope of the existing 1930’s Power Station building. Prior to the commencement of main works, Bauer had to undertake a programme of advanced works, which included preliminary test piling and the removal of old foundations and redundant piles. The piles, which ranged from 300mm diameter to 1200mm dia and at a depth ranging from 12m to over 30m, were removed in the conventional way – driving casing over the top of the piles and breaking them up with destructive drilling gear.

Battersea Power Station The bore was subsequently filled with low strength concrete, with Bauer installing a new pile at that location. Advance works were undertaken between February and June 2016, with obstruction removal and coring continuing throughout the lifespan of the project. Main works followed and included the installation of two very large secant walls inside what was originally Turbine Hall A and Turbine Hall B. Installation was not easy, as access was severely restricted particularly with regards to height. Specifically, over 500 secant piles were installed within what is essentially two basement excavations inside each of the Turbine Halls and will ultimately be commissioned to provide space to house various M&E services as well as residential parking. Turbine Hall A wall was 200 linear metres in length, with a retained height of approximately 8m. Turbine Hall B wall was 160 linear metres in length and has a retained height of approx. 9m.

The project demanded a stringent collaborative approach to working, because of the space and access restrictions, as well as strict building movement tolerances, asbestos contamination, scour features in the London Clay, logistics management and coordinating work with both enabling and follow on contractors. At peak, a multinational team of over 50 employees worked day and night,5 days a week to deliver the project, making logistics one of the most essential components of the project’s success. In particular, Bauer Technologies had circa 60 vehicle movements each day, which required careful and safe management. Formal weekly and daily planning meetings during the entire project, as well as weekly planning meetings with client, contractors and Bauer’s own sub-contractors, which were employed to supply excavators and dumpers and ‘muck away’ trucks, were held to ensure seamless and safe operations. Bauer also had to collaborate closely with other contractors, in order to successfully and safely work within the heavily restricted areas. In fact, before Bauer could access any area the site had to be fully decontaminated and washed down to allow safe access, and this was done well in advance of piling works. Simply getting materials and plant in and getting waste out of the single gate and entrance to the site, was not easy and required close working with Clipfine, the company managing the site-wide logistics. Bauer Technologies had to pre-plan all deliveries 48 hours in advance, through an online ‘booking-in’ system, to ensure slots were available. Having the Logistics Manager attend daily meetings helped enormously. The main plant - 2 no. BG39, 1 no. BG40 and 3 no. crawler cranes - were delivered to site on a low loader, with Bauer working together with Mace to develop access routes into the building and to make sure openings were wide enough. In fact, access was extremely tight and in places only a few centimetres to spare, demanding a careful approach throughout. The BG’s masts were delivered on separate low loaders, together with tooling and Kelly bars.

Battersea Power Station Major loads were required to come in after 10pm, due to transport restrictions in the area. The erection of masts was undertaken in situ, which included building the rigs on site (mast; cat head; ballast weight; winches; rotary drive on the rig) all built by Bauer Technologies UK-based fitters. The BG39 rigs used by Bauer Technologies were brand new and the most advanced energy efficient, environmentally friendly rigs available from The BAUER Group.

The specific scope of work undertaken by Bauer Technologies included the design of permanent and temporary works piled foundations. Installing 500no., 880mm and 1180mm dia secant piles in the two secant walls and the installation of 125no. contiguous wall piles. 400no. bearing piles, ranging from 750mm to 2.4m diameter and to depths of between 35m-65m some of which were permanently cased with slip coated liners to minimise risk to adjacent power tunnels were also installed. 80no. piles for temporary works structures and tower cranes were also installed during the project. Although the project called for a conventional piling technique, the presence of a deep and unusual scour feature in the London Clay, on which Battersea Power Station was built directly on top of, did present a huge challenge for Bauer. There is much debate as to the origin and cause of the scour feature with a number of hypotheses including chalk dissolution; thermokast features; ice wedges and frost heaved diapirs. What is known is that they form typically as a consequence of fluvial or glacio-fluvial processes and can occur in a number of settings, such as confluence of river channels, flooding or meanders. Their depth is usually between 3 to 5 times the depth of the confluent channel and the scour depth increases at higher discharge angles. In this instance the scour feature has eroded the natural profile of the London Clay and created substantial differences in depth to stable clay across the site. Generally, the London clay horizon is 7m from ground level, but this can sharply deepen to 33m in the affected areas. The infill material in the scour feature is not homogenous or stable, comprising very loose silts, sandy gravel and chalk relics. Due to the proximity to the River Thames, the ground water table is affected by diurnal tides, ranging from 2m to 5m below ground level.

The scour infill material is extremely unstable, making pile installation difficult. Construction solutions included installing very long temporary casings to seal into clay, the use of bentonite support fluid or, in some cases, combining the two. Early piling used a ‘casing only’ approach until an 800m3 capacity bentonite plant was established. This was tailored to fit around temporary steel structures and tower cranes within the confines of the existing structure. Later piles were constructed using bentonite from this plant.

Success was also driven by Bauer’s ability to work closely with other contractors in managing the difficult site logistics and the frequent hand over and hand back of work areas. During peak production Bauer Technologies had circa 60 vehicle movements each day to coordinate with the other contractors also working in the structural envelope. Whilst working in this highly congested environment, Bauer Technologies was still able to undertake 5km of coring and nstall over 26km of new pile comprising 36,000m3 of concrete and 6,000T of steel. The Bauer Technologies project team took pride in thinking laterally and presenting options for programme optimisation. Options presented and accepted accelerated the overall programme and allowed earlier than anticipated start for the follow-on contractors.

Battersea Power Station

The project can be considered something of a flagship for Bauer Technologies, as it showcases not only technical ability, but also a collaborative approach, with works completed ahead of schedule. Specifically, the project highlights Bauer’s ability to work safely in a restricted space envelope, using large plant in low head room and restricted working space (No RIDDOR accidents or incidents). Bauer’s adaptable approach and access to manufacturing facilities meant that tools could be designed, modified or reinforced to deal with these obstructions. In fact, the in-house equipment resource and manufacturing capabilities of The BAUER Group proved invaluable for planning and 3D BIM modelling of piling rig configurations to ensure all the pile locations could be accessed by the appropriate heavy-duty piling rig. Noise control measures were also implemented at night to benefit the Phase 1 residents.

Speaking about the project and Bauer Technologies performance on-site Paul Doyle, Project Director for Bauer Technologies, said: “Bauer’s willingness to participate in a highly collaborative programme of works delivered a safe and productive geotechnical solution. Although there were many challenges, Bauer’s high standard of Health & Safety was maintained throughout and its processes and planning allowed operations to be smoothly integrated with other contractors on site for successful project delivery.”

Client: Battersea Power Station Development Company (BPSDC)
Principle contractor: Mace
Piling contractor: BAUER Technologies Limited
Contract period: February 2016 to December 2017
Bauer's Scope of Works: - Design of permanent and temporary works piled foundations
- 500no 880 and1180 mm diameter secant piles in 2 secant walls
- 125no contiguous wall piles
- 400no bearing piles (750mm to 2.4m dia between 35m and 65m deep)
- 80no temporary piles for temporary works structures and tower cranes
- Setting out
- Spoil disposal
- Obstruction and pile removal
- Pile testing
- Materials sampling and testing
Equipment Used: - 2 no. BG39 inc low headroom variant
- 1 no. BG40
- 3 no. Crawler Cranes
- Bentonite plant
Project value: £32 million