Implementing WSPs: Thames Water

Thames Water is the largest water company in the UK serving 13 million customers in London and the Thames Valley. It sources include river and groundwater supplies and it operates 31,100 kilometres of water mains and 100 treatment works.

WSPs are “not particularly new”, according to water quality manager Phil Wakeford. He tracks them back to a requirement introduced in 1999 to conduct risk assessments for the protozoan pathogen cryptosporidium. WSPs are much the same, he argues, but cover all risks.

For Thames, WSPs mean focusing on end users and imagining the water supply seen from a single property or street. Customer-level asset safety plans, or CLASPs, are the company’s term for the process of assessing the risks from source to tap.

The company divides its supply systems into five ‘silos’: catchment, treatment, treated-water storage, distribution and customers. Unusually it regards treated-water service reservoirs as a separate category deserving special attention. There are many considerations at these sites, it reasons, which can influence water quality.

As project manager for WSPs, Mr Wakeford heads a specialist team completing plans across the company – a process which will take “at least two years”, he says.

For the purpose of WSPs Thames divides its supplies into 75 ‘communities’. Some are isolated zones in which a single borehole supplies a village, while others are more complex. For example, in London clusters of treatment works near the rivers Thames and Lea supply local areas and feed into the ring main, which balances supplies around the capital.

Reading – where Thames’ headquarters is based – has been adopted as a test community for the roll-out of WSPs. There is also a team screening other areas for supply risks which may require investment in the next AMP cycle. Feeding into that process are the results of Thames’ regular checks of all five silos, including service reservoirs, distribution systems, information from customer complaints and from surveys of commercial customers with regard to compliance with water fittings regulations.

Thames reported 64 events in 2006, of which 12 were judged incidents likely to affect water supply. The DWI criticised the company over one event where it received complaints of water smelling of fuel oil. It took the company more than a month to correct the problem which was finally traced to a connection with a redundant water main. Thames provided bottled water, but the problem was that its computer mapping system did not show the connection.

The DWI said the incident highlighted the importance of accurate records to risk management. Mr Wakeford agreed, pointing out this is yet another aspect of what WSPs are all about.