Beckton Pumping Station Shaft, Lee Tunnel, UK
Integritank HF protects Beckton Pumping Station Shaft, helping redirect storm water and sewage.
The Thames Water Lee Tunnel is a key part of the Thames Tideway project and is the first stage of improvements to London’s sewer system which will remove combined discharges of storm water and sewage to the River Thames and lower River Lee.
The project requires a number of large tunnels to carry the existing wastewater to Europe’s largest water treatment works in Beckton, East London. A major structure in the project is the Beckton Pumping Station Shaft, measuring 82m deep and 42m wide and at its base, subjected to over eight bar of hydrostatic pressure.
Stirling Lloyd Construction Ltd
- Beckton Pumping Station Shaft, Lee Tunnel
Main Contractor MVB, a joint venture of Morgan Sindall, Vinci Grand Projects and Bachy Soletanche, selected Stirling Lloyd’s Integritank HF spray applied membrane to waterproof the concave base and lower walls of the shaft. Integritank HF was chosen as it provides a number of unique benefits to waterproofing structures of this type. Designed specifically for installation in confined spaces such as tunnels and shafts, the HF membrane can be tested electrically in-situ to confirm its watertightness, and it provides a balance of high performance characteristics including resistance to mechanical damage and abrasion, excellent crack-bridging, and rapid application and cure. The system can also be applied on damp concrete free of surface water.
Application Part 1.
The Beckton Pumping Station Shaft is the largest shaft on the project – enabling the pumping of effluent from the Lee tunnel itself. The shaft was constructed following the sinking of an outer diaphragm wall. Dewatering was established and the shaft excavated. A concave concrete base was then formed by hit-and-miss cast in-situ concrete segments to minimise the possibility of shrinkage cracks. Following the application of the Integritank HF waterproofing membrane a protective screed was laid, onto which an 11,000 tonne concrete base slab was cast in place. An inner structural wall was then cast by continuous slip-forming and the annulus between this and the diaphragm wall in-filled. To house the manifold that carries the liquids into the shaft a Suction Culvert was constructed on the base slab; this culvert was also waterproofed with Integritank HF. Inside the shaft a dividing wall, to the full height of the shaft, was cast and the pumping equipment installed.
To ensure that any movement at the joints between the 150mm thick segments forming the base slab could be controlled. Authorised Contractor Stirling Lloyd Construction applied a stripe coat of Integritank HF along each of the Joints, reinforced with fabric scrim, prior to main membrane installation. The reinforced stripe coat provides additional tensile strength to the membrane across the joint.
Application Part 2
The main membrane installation was also carried out in a segmental pattern to fit in with MVB’s schedule of placement of the 150mm protective screed. The screed was utilised to protect the membrane from a “scaffold” of steel tubes that stand on the waterproofed concrete slab to support the reinforcement mats for the main structural concrete slab.
The rendered walls were then also waterproofed up to a height of 1.8m. Prior to handing over each waterproofed segment area to MVB, Stirling Lloyd Construction completed their installation by non-destructively testing the applied membrane with a “holiday tester”, to confirm that the membrane was fully-waterproof. This capability for confined space tunnel waterproofing is unique to Integritank HF.
The successful completion of the Beckton Pumping Station Shaft, utilising the Integritank HF system will help ensure effective containment of storm water and sewage from the River Thames and lower River Lee. Pumping the wastewater to Europe’s largest water treatment works in Beckton, East London. This was a key part in the Thames Tideway project and was first stage of improvements to London’s sewer system.