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Over 20 Tonnes of Concrete Coatings and Mortars for Liverpool Waste Water Project

Over 20 tonnes of Flexcrete materials has been used on one of the biggest construction sites in Liverpool, a new £200m waste water treatment plant currently being constructed at Wellington Dock, near Kirkdale.

United Utilities is developing the new two-storey Sequential Batch Reactor (SBR) plant in the disused Wellington Dock. Once complete, the plant will serve 600,000 households, taking away their sewage, and treating it to the highest standards before returning it to the River Mersey. It will treat up to 11,000 litres of wastewater a second – the equivalent of filling 16 Olympic-sized swimming pools every hour. The project is on target for the new plant to be up and running by April 2016. The main contractor for the works is GCA (Galliford Try, Costain and Atkins) joint venture.

The site is designed as an extension to the existing treatment works at neighbouring Sandon Dock, the second largest site in United Utilities’ portfolio but one which is no longer capable of handling all of the effluent that goes through it. The new SBR plant stands 21m high, and consists of 16 cells on two levels that are effectively chambers through which water passes during the various stages of secondary treatment. The SBR plant has been constructed using in-situ concrete, based on a network of tall, slim, 500 – 600mm square columns and 600mm thick wall panels.

Flexcrete materials were used to underpin and assure the design life of the new structure by assuring protection of concrete; Flexcrete Unimatch and Monomix were specified and applied by the contractor Bowercross Construction. Unimatch is a single component, cosmetic grade repair mortar which is supplied in grey and white grades to match the parent concrete. It provides a highly aesthetic, waterproof finish with excellent protection against chloride attach, acid gases, moisture ingress. Monomix is a low density, high strength, shrinkage compensated, waterproof cementitious repair mortar which is easily trowellable and can be applied up to thicknesses of 80mm in a single application. Its dense matrix offers low permeability to water, even at 10 bar pressure.

Cemprotec E942, a high performance waterborne, epoxy and polymer modified cementitious coating chosen for this project for the following reasons:

  • It can be applied to damp or green concrete, whilst its water-based composition ensures it cures without the release of hazardous solvents.
  • The dense matrix of Cemprotec E942 offers low permeability to water, even at 10 bar positive and negative pressure.
  • It has a high diffusion resistance to the ingress of chloride ions, oxygen and acidic gasses.
  • It also offers outstanding chemical and abrasion resistance.

All three Flexcrete products are CE marked in accordance with the demands of BS EN 1504.

Around 350 people work at the Wellington Dock site, which is almost the length of two football pitches. As well as the new extension, the existing works in neighbouring Sandon Dock are being improved and a 285m long outfall pipe has been installed on the bed of the Mersey, taking the treated waste water out into the middle of the river.

The project will continue the long-term aim of keeping the River Mersey clean, something which originally began in the 1980’s, when it was heavily polluted and named as the dirtiest in Europe. Since then, United Utilities has spent millions of pounds on the construction of a huge 29km sewer from Crosby to Speke, which carries the city’s wastewater to Sandon Dock. Now, salmon and trout live in the river as a testament to this investment.