Groundworks contractor PJ Carey is currently using the equipment to support a 4.5 m deep excavation which will house part of one of the power station’s two turbine houses.
The project, being undertaken by main contractor Siemens on behalf of Severn Power, is taking shape on the site of the former ‘Uskmouth A’ coal-fired power station near Newport. Using brownfield land and existing grid connection infrastructure, the new 840 MW combined-cycle gas turbine (CCGT) power plant is due to start operating in 2010.
The site of the new turbine house is located on a deposit of pulverised fuel-ash (PFA), a by-product of coal-fired power generation. This material (a useful cement additive) performs poorly in the ground and makes the job of excavating foundations difficult, says Simon Joseph, area manager for Groundforce:
“PFA’s fine when it’s dry, but when it’s wet it’s just like porridge” says Mr Joseph. So to provide a reliable support system, Groundforce specified its GFI(Groundforce Interlocker) trench sheets to provide a secure barrier for the walls of the excavation. “The client wanted a lightweight interlocking system”, adds Mr Joseph.
To take the lateral forces across the 22 m long, 12 m wide excavation, Groundforce supplied its 1500 Series modular heavy duty hydraulic bracing system installed around the perimeter.
With the excavation fully braced, PJ Carey installed its concrete formwork and cast the basement slab and walls. The equipment will soon be re-deployed on one of the many relatively minor excavations which also form part of the project.
Work on site started only in September 2008 and the construction programme is extremely tight. Speed of installation and removal was a key factor in the choice of temporary works, says Carey’s project manager Keith Collier: “It’s extremely fast-track and we’ve relied on Groundforce to deliver quickly and on-time; there have been no problems so far.”
