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Thames Water Utilities Limited – Service Reservoirs, Inadequate Turnover and Chlorine Residual Risk

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

Reference: TMS-2021-00004

Version Number: 3

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:

  • Service reservoirs listed in Annex 1.

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 11 August 2021, which states that there is or has been a significant risk of supplying water from the service reservoirs listed in Annex 1 (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

Inadequate turnover leading to low free chlorine residuals and consequential risk of biological failures.

Chemical

Multiple risk assessment reports (Annex 1). For example: Crystal Palace Cell A

TMS-5-RSR0059-HEID065-RSR0059-H001

Inadequate turnover leading to low free chlorine residuals and consequential risk of biological failures.

Biological

Multiple risk assessment reports (Annex 1). For example: Crystal Palace Cell A

TMS-5-RSR0059-HEID065-RSR0059-H027

Inadequate turnover leading to low free chlorine residuals and consequential risk of biological failures.

Inorganic

Multiple risk assessment reports (Annex 1). For example: Crystal Palace Cell A TMS-5-RSR0059-HEID065-RSR0059-H046

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. Enhanced sampling (in addition to routine regulatory sampling) for coliform bacteria and E. coli, colony counts and chlorine (free and total) at a frequency of twice a week from each service reservoir cell listed in Annex 1.
    Date: Ongoing for the duration of this Notice.
  2. Regular (minimum monthly) site visits for all cells listed, to include site security, service reservoir external inspection and operational equipment checks.
    Date: Ongoing for the duration of this Notice.
  3. Regular Thames Valley and London Water Quality turnover assessment meetings to review chlorine residuals and turnover for service reservoirs.
    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. Undertake a review of turnover and chlorine residual risks for the sites listed in Annex 1. To include:
  • Review the pumping and control strategy of the supplying water treatment works and transmission system. Where applicable, review the blend between chloraminated and chlorinated water and the effect on chlorine residuals.
    Date: Complete.
  • Implement Review the service reservoir turnover trends. Include a review of the operational arrangements for water entering and leaving each cell and turnover within each cell.
    Date: Complete.
  • Review the suitability of the inlet and outlet positioning. The implications on representativeness of sampling should also be considered as part of the review.
    Date: Complete.
  1. Following the review in (b)1 identify any remedial work or additional control measures that are required to improve turnover and chlorine residuals, and develop a plan including timeframes to complete the work required. Where relevant and where turnover within a cell is found to be a potential issue, modelling shall be considered for inclusion within the action plan.
    Date: Complete.
  2. Implement the plan developed in (b)2 and complete any work identified.
    Date: by dates specified in annex 2, column B.
  3. Review Annex 2 on a biannual basis to ensure that service reservoirs that required remedial works in (b)3 and have been completed, are put forward for removal from the annex, or where service reservoirs require adding to the annex, are put forward for addition to the annex where necessary.Date: At least biannually by 31 May and 30 November each year
  4. All Company’s Service Reservoirs: Develop a suitable companywide procedure for monitoring chlorine residuals and turnover to ensure that any potential risk to wholesomeness is identified and actioned in a timely manner.
    Date: Complete.
  5. All Company’s Service Reservoirs: Conduct a gap analysis to identify any sites where chlorine and turnover may present a potential risk to wholesomeness using the new procedure developed in (b)4.
    Date: Complete.
  6. All Company’s Service Reservoirs: Implement the appropriate actions, in accordance with the new procedure, to address the findings of the gap analysis completed under (b)5.
    Date: Complete.
  7. All Company’s Service Reservoirs: Implement the procedure developed under measure (b)4, train relevant personnel on the procedure, and implement a ‘business as usual’ forward-reaching programme of review and training for the new procedure.
    Date: Complete.

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

  1. Define an audit strategy to monitor the effectiveness of the above measures specified in section (a) and (b), including an audit into turnover and chlorine residuals 12 months following the implementation of mitigation measures.
    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 listed service reservoirs in annex 1, 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. Provide a summary of the review as stipulated in (b)1. and confirm any remedial work or additional control measures required to improve turnover and chlorine residuals, as specified in step (b)2, including the plan with proposed timeframes to complete any work required.
    Date: Complete.
  3. Confirm completion of the plan and any work required, as specified in (b)3.
    Date: 1 month following the dates specified in Annex 2, column B.
  4. Submit the revised annex to the Inspectorate as required in measure (b)4, outlining any changes that are required.
    Date: One month after the biannual review, with a submission date of 30 June or 31 December each year.
  5. Provide the procedure developed for monitoring chlorine residuals and turnover, as specified in (b)4.
    Date: Complete.
  6. Provide evidence that the procedure has been implemented and that relevant personnel have been trained on the new procedure, as specified in (b)7.
    Date: Complete.
  7. Confirm completion of gap analysis and any sites where chlorine and turnover may present a potential risk to wholesomeness, as specified in (b)5. Confirm the projected completion date for (b)6.
    Date: Complete.
  8. Confirm completion of measure (b)6.
    Date: Complete.
  9. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete.
  10. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  11. 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
  12. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: By the dates specified in Annex 2, Column C for each individual service reservoir.

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
24 October 2024
Reference: TMS-2021-00004 v3

Annex 1 – Categorisation of sites included in this notice, reference numbers and relevant Hazard IDs.

Site name

Site reference

Hazard IDs

Okus

RSR0256

TMS-5-RSR0256-HEID065-RSR0256-H027

TMS-5-RSR0256-HEID065-RSR0256-H046

TMS-5-RSR0256-HEID065-RSR0256-H047

Burford B

RSR7087

TMS-5-RSR7088-HEID065-RSR7087-H027

TMS-5-RSR7088-HEID065-RSR7087-H046

TMS-5-RSR7088-HEID065-RSR7087-H047

Worsham A

RSR7145

TMS-5-RSR7145-HEID065-RSR7145-H027

TMS-5-RSR7145-HEID065-RSR7145-H046

TMS-5-RSR7145-HEID065-RSR7145-H047

Worsham B

RSR7146

TMS-5-RSR7145-HEID065-RSR7146-H027

TMS-5-RSR7145-HEID065-RSR7146-H046

TMS-5-RSR7145-HEID065-RSR7146-H047

Worsham C

RSR7128

TMS-5-RSR7145-HEID065-RSR7128-H027

TMS-5-RSR7145-HEID065-RSR7128-H046

TMS-5-RSR7145-HEID065-RSR7128-H047

Worsham D

RSR7129

TMS-5-RSR7145-HEID065-RSR7129-H027

TMS-5-RSR7145-HEID065-RSR7129-H046

TMS-5-RSR7145-HEID065-RSR7129-H047

Blacklains A

RSR7095

TMS-5-RSR7095-HEID065-RSR7095-H027

TMS-5-RSR7095-HEID065-RSR7095-H046

TMS-5-RSR7095-HEID065-RSR7095-H047

Blacklains B

RSR7096

TMS-5-RSR7095-HEID065-RSR7096-H027

TMS-5-RSR7095-HEID065-RSR7096-H046

TMS-5-RSR7095-HEID065-RSR7096-H047

Sewardstone Green A

RSR0306

TMS-5-RSR0306-HEID065-RSR0306-H027

TMS-5-RSR0306-HEID065-RSR0306-H046

TMS-5-RSR0306-HEID065-RSR0306-H047

Sewardstone Green B

RSR0017

TMS-5-RSR0306-HEID065-RSR0017-H027

TMS-5-RSR0306-HEID065-RSR0017-H046

TMS-5-RSR0306-HEID065-RSR0017-H047

Headington A

RSR6037

TMS-5-RSR6037-HEID065-RSR6037-H027

TMS-5-RSR6037-HEID065-RSR6037-H046

TMS-5-RSR6037-HEID065-RSR6037-H047

Headington B

RSR6038

TMS-5-RSR6037-HEID065-RSR6038-H027

TMS-5-RSR6037-HEID065-RSR6038-H046

TMS-5-RSR6037-HEID065-RSR6038-H047

Bishops Wood A

RSR0352

TMS-5-RSR0352-HEID065-RSR0352-H027

TMS-5-RSR0352-HEID065-RSR0352-H046

TMS-5-RSR0352-HEID065-RSR0352-H047

Bishops Wood B

RSR0353

TMS-5-RSR0352-HEID065-RSR0353-H027

TMS-5-RSR0352-HEID065-RSR0353-H046

TMS-5-RSR0352-HEID065-RSR0353-H047

Cockfosters A

RSR0006

TMS-5-RSR0006-HEID065-RSR0006-H027

TMS-5-RSR0006-HEID065-RSR0006-H046

TMS-5-RSR0006-HEID065-RSR0006-H047

Cockfosters B

RSR0300

TMS-5-RSR0006-HEID065-RSR0300-H027

TMS-5-RSR0006-HEID065-RSR0300-H046

TMS-5-RSR0006-HEID065-RSR0300-H047

Crystal Palace A

RSR0059

TMS-5-RSR0059-HEID065-RSR0059-H027

TMS-5-RSR0059-HEID065-RSR0059-H046

TMS-5-RSR0059-HEID065-RSR0059-H047

Crystal Palace B

RSR0316

TMS-5-RSR0059-HEID065-RSR0316-H027

TMS-5-RSR0059-HEID065-RSR0316-H046

TMS-5-RSR0059-HEID065-RSR0316-H047

Darnicle Hill A

RSR0301

TMS-5-RSR0301-HEID065-RSR0301-H027

TMS-5-RSR0301-HEID065-RSR0301-H046

TMS-5-RSR0301-HEID065-RSR0301-H047

Darnicle Hill B

RSR0009

TMS-5-RSR0301-HEID065-RSR0009-H027

TMS-5-RSR0301-HEID065-RSR0009-H046

TMS-5-RSR0301-HEID065-RSR0009-H047

Eltham A

RSR0293

TMS-5-RSR0292-HEID065-RSR0293-H027

TMS-5-RSR0292-HEID065-RSR0293-H046

TMS-5-RSR0292-HEID065-RSR0293-H047

Eltham B

RSR0292

TMS-5-RSR0292-HEID065-RSR0292-H027

TMS-5-RSR0292-HEID065-RSR0292-H046

TMS-5-RSR0292-HEID065-RSR0292-H047

Oxleas Wood A

RSR0048

TMS-5-RSR0048-HEID065-RSR0048-H027

TMS-5-RSR0048-HEID065-RSR0048-H046

TMS-5-RSR0048-HEID065-RSR0048-H047

Oxleas Wood B

RSR0312

TMS-5-RSR0048-HEID065-RSR0312-H027

TMS-5-RSR0048-HEID065-RSR0312-H046

TMS-5-RSR0048-HEID065-RSR0312-H047

Stokewood 1

RSR0165

TMS-5-RSR0165-HEID065-RSR0165-H027

TMS-5-RSR0165-HEID065-RSR0165-H046

TMS-5-RSR0165-HEID065-RSR0165-H047

Stokewood 2

RSR0166

TMS-5-RSR0165-HEID065-RSR0166-H027

TMS-5-RSR0165-HEID065-RSR0166-H046

TMS-5-RSR0165-HEID065-RSR0166-H047

Table 2 Categorisation of sites included in this notice, reference numbers and relevant Hazard IDs

Annex 2 – Dates

Service Reservoir Name and Reference Number

Date by when all (b) measures are to be completed by

Date by when the completion report is due, following 12 months of successful audit and 1 month for report compilation

Okus SR – RSR0256

31 December 2026

31 January 2028

Worsham A – RSR7145

Worsham B – RSR7146

Worsham C – RSR7128

Worsham D – RSR7129

31 December 2026

31 January 2028

Sewardstone Green A – RSR0306

Sewardstone Green B – RSR0017

31 March 2026

30 April 2027

Blacklains A – RSR7095


Blacklains B – RSR7096

31 March 2028

30 April 2029

Sewardstone Green A – RSR0306


Sewardstone Green B – RSR0017

31 March 2026

30 April 2027

Headington A – RSR6037

Headington B – RSR6038

31 December 2026

31 January 2028

Bishops Wood A – RSR0352

Bishops Wood B – RSR0353

31 December 2028

31 January 2030

Cockfosters A – RSR0006

Cockfosters B – RSR0300

31 March 2026

30 April 2027

Crystal Palace A – RSR0059

Crystal Palace B – RSR0316

31 March 2027

30 April 2028

Darnicle Hill A – RSR0301

Darnicle Hill B – RSR0009

31 December 2028

31 January 2030

Eltham A – RSR0293

Eltham B – RSR0292

30 April 2026

31 May 2027

Oxleas Wood A – RSR0048

Oxleas Wood B – RSR0312

31 December 2028

31 January 2030

Stokewood 1 – RSR0165

Stokewood 2 – RSR0166

31 December 2026

31 January 2028

Table 3 Dates by site, for completion of all (b) measures and for the completion report submission
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