The protection and mitigation scheme was developed by Yorkshire Water and East Riding of Yorkshire Council following several years of serious flooding caused by storm water run-off overwhelming the drainage system in the town of Beverley.
Preventative measures involved increasing the capacity of the sewerage system, erecting a flood protection wall and constructing the new 80,000 litre detention tank known as ‘Beverley Shaft’ to hold run-off water until a storm has passed and the drainage system has returned to equilibrium. Pumps in the tank then return the contaminated water back to the drains for treatment.
The shaft’s construction adjacent to a drinking water aquifer meant it had to be lined with a durable waterproofing membrane to contain the contaminated sewage and run-off water and prevent it from reaching the drinking water supply. As a result, design and build contractor, Mott MacDonald Bentley specified the application of 500m² of Stirling Lloyd’s Integritank HF system.
Designed specifically for installation in confined spaces such as tunnels and shafts, the system is a spray-applied polymer membrane that combines rapid application and cure with high impermeability. The application of a fast curing penetrative primer, allowing application to a damp substrate, was followed by two high contrast membrane coats, each of 1.5mm, with the first coat pigmented yellow and the second, pigmented white. The contrasting colours help the sprayer to ensure all areas are adequately covered.
In addition to the visual guide provided by two colour-coded coats, the thickness of each coat is measured during application by wet film thickness tests to verify that the membrane is being installed as specified. Post application, while the contractor is still on-site, integrity is confirmed by ‘holiday testing’ ensuring a defect-free, waterproof surface is achieved.
Image – The white coat goes on top of the yellow to ensure the surface is entirely covered.