The Challenge:

Located on a vast site in North London, Deephams is one of the capital’s largest facilities. It provides sewage treatment and sludge processing to a population of 891,000 as well as storm water storage. The plant services three major sewers at different levels with a dry weather flow of 232,000 cubic metres a day.

We were involved in a Thames Water’s project at Deephams to upgrade the 50 year old site to meet new Environment Agency sewage treatment standards. The site also needed to meet the needs of approximately one million people, reduce odour and improve the quality of discharge into the River Lea. The challenge at Deephams was to demolish and rebuild the sewerage works whilst not compromising the quality of the treatment process. This involved having a good knowledge of the treatment process to intercept and change the route flows to suit our current programme.​

The Solution:

The construction project activities included a large amount of temporary works including:

  • De-watering works
  • Sheet piled cofferdams
  • Extensive diamond drilling
  • Complex formwork and falsework designs
  • Temporary flow diversion channels
  • Soil stabilisation
  • Muck storage

The permanent works involved:

  • Large RC structures
  • Sewer culverts
  • Complex MEICA systems worth £50m
  • Odour control systems that capture and treat the odour to achieve a 99% odour reduction

A combined heat and power system turned methane gases into electricity to power the whole sewage treatment plant. This generated £1m revenue from surplus electricity by sending it back to the grid.

We aimed for a highly sustainable design to meet the client’s requirements. To achieve this each design was challenged and all options were considered to calculate whole life costs and to gain best value for money.

The Impact:

The results of this approach enabled us to reuse and change existing structures by incorporating them into the final design. We added 2m of height to the treatment plant process to prevent a backflow of water into the treatment facility should the river flood.

Directly next to the works there is a site of special scientific interest and a housing estate, so achieving planning permission was a significant challenge. To achieve consent we looked at each individual part of the works to learn the impact to the local environment and community.

The reconstruction of the works highlighted a range of cutting edge innovations. We focused on increased operational safety, sustainable building techniques and extensive hydraulic modelling to provide significant capacity improvements to the sewage treatment works.

" The interface with the Thames Water Operations Team was critical to the works as sewage treatment never stops on site. In case of storm flow conditions - where there is a danger of flooding - an emergency plan was jointly developed to alter the sewage flow routes to accommodate the increased volume of water and provide a safe system of working for construction operatives. "

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