Thames Water Utilities Limited – Interstage Assets Ingress Risk

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

Reference: TMS-2021-00003

Version Number: 5

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:

• T01U.187 Wanstead
• T02S.002 Hornsey
• T02U.236 Waltham Abbey
• T06U.613 Speen
• T06U.615 Bishops Green
• T06U.621 Ufton Nervet
• T06U.628 Playhatch
• T06U.630 Pangbourne
• T06U.643 Sheeplands 1 Bowsey
• T06U.638 Sheeplands 2 District

Details of this Notice:

1. The Drinking Water Inspectorate (‘the Inspectorate’) has received multiple regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company between 17 October 2019 and 22 January 2021 which state that there is or has been a significant risk of supplying water from the following water treatment works (WTW) (and associated assets as applicable): Pangbourne, Wanstead, Hornsey, Waltham Abbey, Speen, Ufton Nervet, Playhatch, Bishops Green, Sheeplands 2 Bowsey, Sheeplands 2 District, 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
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Cryptosporidium
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Biological
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Physio-chemical
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Metals
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Inorganic
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	E. coli
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Total coliforms
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Enterococci
Ingress route through aeration process. Failure of aeration of process. Insufficient maintenance of treatment/monitoring equipment. Network impact due to aerator being out of supply.	Contamination

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.

3. 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. Treated water continuous Cryptosporidium monitoring at Playhatch WTW, Pangbourne WTW, Speen WTW, Ufton Nervet WTW and Sheeplands WTW. Any positive detection must be investigated in-line with regulatory requirements and include an investigation of all upstream treatment process assets.
   Date: Ongoing for the duration of this notice.
2. Where aerators are expected to be out of supply in the medium to long term, maintain enhanced appropriate monitoring and control measures, dependent upon the treatment function of the aerator.
   Date: Ongoing for the duration of this notice.
3. Ongoing maintenance inspection of aerators.
   Date: Ongoing for the duration of this notice.
4. Enhanced operational monitoring and control measures (to be defined in the audit strategy) at Playhatch WTW, Pangbourne WTW, Speen WTW, Ufton Nervet WTW, Sheeplands WTW and Hornsey WTW to identify any occurrence of interstage asset ingress.
   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. At Pangbourne WTW, Wanstead WTW, Hornsey WTW, Waltham Abbey, Speen WTW, Ufton Nervet WTW, Playhatch WTW, Bishops Green WTW and Sheeplands WTW:

• Complete a risk review of all interstage assets.
  Date: Complete.
• Establish an appropriate risk-based procedure for interstage asset (including aerators) monitoring and maintenance (internal & external). This is to include routine inspections and maintenance as well as full internal and external inspections and cleaning.
  Date: Complete.
• Implement the new procedure established under (b)1b) above. Implementation must include training of relevant personnel.
  Date: Complete.

2. Design appropriate mitigation to address the risk of ingress from interstage assets.
   Date: Complete.
3. Install and commission the designed mitigation (from measure (b)2) to address the risk of ingress from interstage assets.
   Date: Sheeplands WTW – Complete.
   Playhatch WTW, Pangbourne WTW and Speen WTW – 31 December 2025.
   Ufton Nervet WTW – 31 March 2025.

(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: Complete.
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 Playhatch WTW, Speen WTW or Pangbourne WTW, or not to so supply unless the specified conditions below are satisfied:

1. Not to supply water from Playhatch WTW, Speen WTW or Pangbourne WTW via the aerator units until measure (b)3 has been completed at each corresponding site unless all the following conditions are met at the specified WTW:

• A full investigation into the risk to drinking water quality posed by the use of the aerator is completed; and
• Appropriate actions to mitigate the identified risks have been completed.
  Date: Until the completion of measure (b)3. at the corresponding WTW.

(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. A summary of the risk review completed and a copy of the new procedure established under measure (b)1.
   Date: Complete.
3. Confirmation of the implementation of the new procedure and appropriate training required under measure (b)1.
   Date: Complete.
4. Outline of the mitigation design required under measure (b)2 and confirm dates for the completion of measure (b)3 for the individual WTWs.
   Date: Complete.
5. Confirmation of the installation and commissioning required under measure (b)3.
   Date: Sheeplands – Complete.
   Ufton Nervet – 30 April 2025.
   Playhatch, Speen and Pangbourne – 31 January 2026.
6. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
   Date: Complete.
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: 28 February 2027.

Further Details of this Notice:

4. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
5. 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.
6. 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).
7. Contravention of a regulation 28(4)(d) requirement is an offence under regulation 33(1). If guilty of such an offence, the Company is liable on summary conviction, or on conviction on indictment, to a fine. Under regulation 33(2) it is a defence for the Company to show that it took all reasonable steps and exercised all due diligence to avoid the commission of the offence.

Signed

 

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
9 December 2024.
Reference: TMS-2021-00003 v5