The upgrade of the Deepham’s sewage treatment works in London aimed to significantly enhance the capacity of the existing ageing plant. The new pumping station required a shaft of internal diameter of 18.5m and an invert depth of 21m to provide operational freeboard to the invert of a low-level sewer, 15m below ground level. To account for the overall permanent design, including a 600mm thick in-situ concrete lining and a 3.5m deep base plug, the temporary shaft required a 24m deep excavation.
ByrneLooby was appointed by Murphy to develop a solution utilising secant pile techniques. Originally diaphragm walling was specified due to the depth of the shaft. The final design challenged traditional techniques as it pushed the limits of acceptable secant pile depths in the UK. The project was the winning entry in the Concrete Society Awards Civil Engineering category. This recognised the innovative use of the permanent lining as temporary ring beams whilst maintaining a high-quality finish, in addition to the innovations incorporated into the secant pile design.