EPCM was contracted to conduct the design of a subsea temporary sheet-piled cofferdam for the retrieval of a Tunnel Boring Machine (TBM). Cenpower Generation Company Limited of Ghana (Cenpower) developed a new natural gas-fired power station in Tema, Ghana. Group Five International was appointed as the EPC contractor for the cooling water system of the power station.
The offshore components of the cooling water system broadly include two large diameter marine pipelines (installed via horizontal tunnelling), an offshore submerged intake and – diffuser structure. Following pre-dredging tests with regards to the offshore extraction of the TBM, it was considered not feasible to dredge an unrestrained open pit for TBM receiving due to the high sediment transport rates at the offshore site (filling in a pit of approximately 500m3 overnight).
EPCM was requested to assist with the design of a cofferdam using available material (sheet-piles) to retain the collapse of the pit and allow the safe extraction of the TBM with a custom made lifting barge.