In 2004, the World Health Organisation issued guidelines for drinking water quality which recommended that water suppliers develop and implement “Drinking Water Safety Plans” (DWSPs) in order to systematically assess and manage their risks.
Severn Trent Water developed DWSPs for all its sources in 2008. However, a review of these initial plans identified areas in which they could be reassessed. During July 2010 to May 2011 we provided six staff members on secondment to Severn Trent to work as part of a team reviewing and revising the DWSPs. Through the use of a comprehensive risk assessment and risk management, all the potential on-site and off-site risks to catchment areas were assessed.
The DWSP process provides the foundations for risk scoring of potential contaminants and prioritisation of sites. The DWSP team needed to have experience and expertise in water abstraction, treatment and distribution and the hazards that can affect safety through the supply system. Site visits were undertaken to confirm the knowledge, information and schematics available to the utility company, and desk study surveys were completed to collate available environmental and hydrogeological data. A rolling review plan was prepared in order to keep scores up to date and continue the close monitoring of on-site and off-site risks to catchment areas.