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Thames Water Utilities Limited – Sheeplands Works Ingress and Backflow

Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended)

Reference: TMS-2026-00002

Version Number: 1

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:

  • T06U.643 Sheeplands 1 Bowsey

Details of this Notice:

  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 18 June 2026, which states that there is or has been a significant risk of supplying water from Sheeplands 1 Bowsey (and associated assets as applicable) that could constitute a potential danger to human health or 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:

Description of Risk

Hazard/ Hazardous Event/ Parameter

Hazard I D


Backflow from the distribution network into the treatment works. Ingress risk associated with the on-site treated water mains.

Total coliforms (confirmed)


TMS-4-T06U.638-MDCT004-T06U.643-C001

Table 1: Table of the hazards, hazardous events, and/or parameters covered by this Notice, including the Hazard I D numbers and the description of risks.

  1. The company are required to satisfy the following requirements.

The date given is that until or by which the requirements must be maintained or satisfied, as appropriate.

Requirements:

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

  1. Operation of all treatment processes at Sheeplands works, within defined operating ranges with appropriate triggers, responses, and contingency arrangements.
    Date: Ongoing for the duration of this Notice
  2. Enhanced operational monitoring for bacteriological parameters for the drinking water leaving Sheeplands works.
    Date: Ongoing for the duration of this Notice
  3. Water Quality response procedures in place for investigation of contraventions including process optimisation and reporting, consumer complaints and event response.
    Date: Ongoing for the duration of this Notice
  4. Maintain contingency plans for the protection of public health associated with drinking water quality, to include liaison with Local Authorities and the United Kingdom Health Security Agency (UKHSA).
    Date: Ongoing for the duration of this Notice

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

  1. Complete replacement of booster pump non-return valves to mitigate the risk of backflow at Sheeplands Works.
    Date: 31 October 2026
  2. Complete replacement of recoil valves post-booster pumps at Sheeplands Works.
    Date: 31 May 2027
  3. Confirm remedial actions to mitigate against the risk of ingress associated with on-site treated water mains.
    Date: 31 July 2027
  4. Complete remedial actions to mitigate against the risk of ingress associated with on-site treated water mains.
    Date: 30 April 2029

(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 sections (a) and (b).
    Date: 31 October 2026
  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 Sheeplands 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.
    Date: by 31 January each year.
  2. Confirm replacement of booster pump non-return valves as specified in measure (b)1.
    Date: 30 November 2026
  3. Confirm replacement of recoil valves as specified in measure (b)2.
    Date: 30 June 2027
  4. Provide the plan with timescales for remedial actions as specified in measure (b)3.
    Date: 31 August 2027
  5. Confirm completion of measure (b)4.
    Date: 31 May 2029
  6. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: 30 November 2026
  7. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  8. Submit a report in the event that any completed measures of this Notice need to be altered in any way, for any reason.
    Date: Ongoing for the duration of this Notice
  9. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 31 May 2030

Further Details of this Notice:

  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).

Signed

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
25 August 2026
Reference: TMS-2026-00002 v1


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