Current improvement programmes

Notice of Regulation: Clatford Water Treatment Works


Thames Water Utilities Limited: Clatford Water Treatment Works, Bentazone Risk

Reference: TMS-2021-00005

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Thames Water Utilities Limited, with registered number 02366661 (hereinafter called ‘the Company’).

Assets affected:
Clatford Water Treatment Works (T07U.713)
Clatford Catchment (C07U.713)

  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received a regulation 28(1) report of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 22 January 2021, which states that there is or has been a significant risk of supplying water from Clatford Water Treatment Works (and associated assets as applicable) that could be unwholesome.
  2. Consequently, this Notice is served on the Company by the Inspectorate on behalf of the Secretary of State, under regulation 28(4) for the assets listed above, for risks associated with:

Hazard/Hazardous Event/Parameter

Hazard ID

Description of Risks




Detection of the pesticide bentazone in the raw water above the drinking water standard.

  1. The Company are required to satisfy the following:


(a) to maintain the following measures for the period specified in each case:

  1. Enhanced operational monitoring for bentazone in the raw and treated water. Report any operational bentazone exceedances in the treated water to the Inspectorate as soon as practicable.
    Date: Ongoing for the duration of the Notice
  2. Liaison with relevant health authorities as appropriate to inform the assessment of risk to human health.
    Date: Ongoing for the duration of the Notice
  3. Ongoing investigations into potential sources of bentazone in the catchment. Including, targeted catchment liaison initiatives with relevant stakeholders.
    Date: Ongoing for the duration of the Notice

(b) to review, revise or make operational the following measures, by the dates specified in each case:

To mitigate the risk of bentazone above the prescribed concentration, in the water supplied from Clatford Water Treatment Works:

  1. Complete initial feasibility scoping so as to confirm the preferred solution for progression to design.
    Date: 28 February 2022
  2. Complete the design of the preferred solution identified in measure (b)1. above.
    Date: TBC
  3. Implement the preferred solution identified under measure (b)2. above.
    Date: TBC

(c) to audit whether the measures have been effective by the following means:

  1. Define an audit strategy to monitor the effectiveness of the measures specified in section (a) and (b).
    Date: 31 January 2022
  2. Implement, and keep under continuous review, the audit strategy defined in measure (c)1.
    Date: Following completion of measure (c)1. onwards

(d) not to supply water for regulation 4(1) purposes from Clatford Water Treatment Works, or not to so supply unless the specified conditions below are satisfied:

  1. Not applicable

(e) to provide the following information in the time and manner specified below to enable monitoring of progress towards the mitigation of the risks:

  1. Provide a progress report annually by 31 January and against the following milestones:
    Date: Annually by 31 January
    • Outline the feasibility scoping outcome and the preferred option being progressed to design, as required under measure (b)1. Confirm the date for completion of measure (b)2.
      Date: 31 March 2022
    • Report outlining the design of the preferred solution to mitigate the identified risk, as required under measure (b)2. Confirm the date for completion of measure (b)3.
      Date: TBC
    • Confirmation of the implementation of the preferred solution, as required under measure (b)3.
      Date: TBC
  2. Submit the strategy for auditing the effectiveness of the measures, as specified in (c)1.
    Date: 28 February 2022
  3. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  4. Submit a report in the event that any completed measure of this Notice needs to be altered in any way for any reason.
    Date: Ongoing for the duration of this Notice
  5. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: TBC

  1. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
  2. Under regulation 28(6) the Inspectorate, on behalf of the Secretary of State, may by notice served on the Company, revoke or vary this Notice.
  3. Failure by the Company to comply with this Notice may result in enforcement proceedings under section 18 of the Water Industry Act 1991(as amended).

Nick Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
13 January 2022
Reference: TMS-2021-00005
Version 2