A tough Freshwater Fisheries Directive undertaking imposed new ammonia consent standards at Esher Sewage Treatment Works, solved by a Black and Veatch and Costain project completed well within budget.

The Trident Alliance of Black and Veatch and Costain has enabled Thames Water to achieve a tough Freshwater Fisheries Directive undertaking that imposed new ammonia consent standards at Esher sewage treatment Works. Significantly, Black and Veatch and Costain delivered a first-class solution to its client's needs at a total project cost of less than GBP5M - compared to an original estimate of GBP7M. Bringing major environmental enhancements to the Surrey area, one of the main innovations that resulted in large cost savings on design and construction was the introduction of a combined pumping station and two-stage anoxic zone within a single glass-coated steel tank.

'I really admire the beauty of the finished project.

We also accomplished the project below control cost, which is another bonus.

Black and Veatch and Costain must be congratulated on the completion of a very successful contract,' said Ann Weston, Thames Water Project Manager at Esher.

The complex commissioning phase of the project required detailed planning by the entire project team at the commissioning workshops.

These brought about the conversion of Esher STW from two separate process streams, filter and crude ditch, into a single settled sewage ditch stream, with clearly defined routes and processes for the sludge flows.

At the workshops, the interdependency of each item to be commissioned was analysed to determine the correct commissioning sequence.

Contingency plans were also discussed in the event of any process area failing.

The construction team also worked more than 50,000 hours with zero reportable accidents.

Black and Veatch was highly innovative in its methods of construction, including the use of hydro-demolition, instead of using traditional hand-held heavy breakers, which can lead to hand arm vibration syndrome.

'Thames Water Operations are very pleased with the result as they now have a plant that is within the quality consent and working well, allowing them to continue meeting the needs of local residents in a safe, reliable and cost-effective manner,' said Chris Scott, Project Director for Black and Veatch.