Project V Subsea Cable Factory

The project represents a significant investment in the North East on the site of the former Blyth power station and builds on our experience in the energy sector. Careys are delivering a number of key packages on this large-scale scheme.

• Substructure concrete works comprising pile caps and pad foundations

• Process equipment RC pits and plinths

• Ground floor industrial floor slab and upper composite slabs

• External civils works including roads construction (excluding tarmac works), service yard RC slabs, external foul and surface water drainage networks

• Waterproofing

• Construction of a 7 m deep 7m deep circular cofferdam at 19m diameter to allow the excavation and construction of the Vertical Layup Machine (VLM) pilecap and embedded support ring (the VLM is used for manufacturing the subsea cables)

• We are undertaking temporary works design responsibility for the cofferdam and temporary steel support structure (which supports the large cast-in HD ring), in addition to bespoke formwork design.

• Close coordination with other key supply chain partners, specifically around the steel erection, roofing and cladding is also paramount to maximise efficiency and reduce programme risk.

Stakeholder engagement from the outset of Project V has encouraged collaborative working across all temporary works activities. As an experienced contractor delivering temporary works we have worked closely with the client, the permanent works designer, and all relevant stakeholders to carry out design workshops where we shared best practices and demonstrated positive results derived from lessons learnt, shared innovation and collectively worked together to mitigate risk through open discussion.

Our temporary works procedure, ensures that all temporary works are designed, specified, constructed, used, and dismantled in a safe and controlled manner. The design and selection of formwork systems played a critical role in ensuring both the structural stability and the construction efficiency of the project. The site team and the temporary work designer in close collaboration worked to provide an optimised formwork system for casting the pits, ensuring a safe, efficient and robust solution. The formwork design has be developed based on the pour layout and sequence of each pit and checked again once props were fixed to blinding and installed. The formwork has subsequently been aligned upon installation, and checked again prior to concrete pour.

The project involved managing a high volume of embedded items (relics) within the concrete structure. Under Galliford Try, we navigated a series of complex site challenges, including 75-year-old reinforced concrete foundations and culverts with contaminated water.

To date on Project V we have poured in excess of 30,396m3. Concrete mix design, has specifications required to meet performance parameters. To ensure we achieved these benchmarks, each pit was independently programmed and a pour layout developed, average pours lasted 8 hours and consisted of more that 500 m3 of concrete. To ensure these pours successful, consideration and mitigation processes were put in place to monitor the temperature of the concrete, tolerances for cast ins, site constraints and logistics for wagons. Large concrete pour activities have often included industrial ground floor slabs, requiring precise resource management and innovative engineering.

Watertight construction has been a core focus when delivering the pits. To ensure comprehensive thermal control throughout for large concrete pours, we employ thermal modelling to predict temperature rises and gradients, carried out temperature monitoring and insulation during curing and implemented strategies to prevent early age thermal cracking and delayed ettringite formation.

The degassing pit structure was composed of several pits at varying levels, with construction carried out in stages, starting from the central pit. Waterproofing the joints between these pits presented a significant challenge due to the differences in elevation. To ensure a watertight seal, specialised prefabricated water bar units were designed and installed at the joints.

For the construction of the entire structure more than 20 tones of steel reinforcement and 30,396 m3 of concrete has been used to date.

A challenge successfully delivered is the excavation and construction of the Vertical Layup Machine (VLM) pile cap and embedded support ring. This required a 7m deep, 19m diameter cofferdam, with temporary works and bespoke formwork designed to support large cast-in HD rings. Once cast, the cofferdam was sacrificed, cut to level, and integrated into a circular retaining wall.

Managing change effectively on Project V has been of critical importance to minimise potential time and cost risks. Our ability to respond to change, demonstrates our capability in contingency planning, resource management, and subcontractor coordination for a complex, large-scale infrastructure.

As the project has progressed we have adapted to process equipment driven design adjustments, mitigating programme impacts through collaboration. Close coordination with the client and other stakeholders has ensured seamless steel erection, roofing, and cladding. This approach has ensured we managed additional works which were integrated into our scope without disrupting delivery.