Before work began, one-metre-deep trial holes were excavated to assess existing ground conditions. This information helped inform external designers to determine the thickness of the stone foundation required for the new six-metre-diameter, ground-supported concrete sludge tank base.
Once a design had been approved by the client, the Stonbury team began the groundwork with a five-tonne tracked digger to excavate the area to a level formation. A foundation of 150mm-thick compacted Type 1 stone was applied on a geosynthetic layer of Terram, which enables drainage without the loss of fines and the resultant aggregate destabilisation.
Steel reinforcement bars and circular formwork were then installed to receive the concrete – forming a reinforced, level concrete base. Six pipework supports were also built on concrete bases using solid concrete blocks to support the delivery pipework.
Once the concrete had cured, the formwork was removed and the area around the base was reinstated, ensuring good access for the tank constructors. The project has now been handed over to a second contractor for the steel tank build. Stonbury will return after tank construction and pipe installation to complete gravel reinstatement and seed the top-soiled area.