Deephams Sewage Treatment Work major upgrade project

Project achievements and benefits

The improvements to the quality of the final effluent leaving the works have a direct positive impact on the downstream river environment and aquatic life.

The works also have improved the management of invasive species such as Japanese knotweed. The plant now removes a higher percentage of organic matter and solids from the flow while generating more renewable energy from the new combined heat and power (CHP) plant.

By maximising the value from the process in this way, on average, two-thirds of the energy requirements for the site is self-generated using renewable sources.

The biggest improvement to the immediate local community is the elimination of bad smells from the site. This is a result of covering the entire inlet works and most sources of odour.

Finally, as part of the upgrade works an education centre has been added to the site, which will be run in partnership with Thames Water’s education team and will support the engagement and education of the current and future customers in the area.

How the work was done

There were four distinct phases of work during the construction – early, temporary, intermediate and permanent – to enable continuous operation of the works during construction.

To make sure that the site could work at an optimum level throughout the temporary phase, a temporary pumping and hydraulic balancing were required to lift flows through uncompleted parts of the work.

The construction programme and site layout were complicated by the need to build in one stream at a time, demolishing and phasing construction around the existing treatment plant to maintain the capacity of flow and this drove the programme for the permanent design.

This phased work brought about interesting challenges, such as when three-quarters of a new flow splitter structure had to be built and commissioned and the last quarter built at a later stage. This led to temporary and permanent structures being combined.

A trench-style pumping station was designed for the main influent pumping and the innovative self-cleaning design of the wet well removed the need for manual access in the future for cleaning, as pumps hanging from above can be removed without needing someone to access the confined space.

The original stormwater pumping station was designed to only need to pump when the river level is at storm flood level.

Use of innovative technology to design and construct the work was key to the success of this project.

Using BIM modelling technology, a full 3D Revit model was used from the start to design the project and ensure clash detection across the site and a BIM level 2 environment was created to support the design review, construction planning and delivery process.

Throughout the construction phase, drones were used to keep a photographic record of the works, assist construction planning and to identify good practice, such as site tidiness. This has also provided a highly useable asset management legacy.