Thames Water Utilities Limited – Farnborough Service Reservoir Chain, Inadequate Turnover and Chlorine Residual Risk

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

Reference: TMS-2021-00002

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:

Asset Name	Reference
Farnborough A Service Reservoir Farnborough B Service Reservoir Farnborough C Service Reservoir Farnborough D Service Reservoir	RSR0328 RSR0327 RSR0325 RSR0326
Knockholt New North Service Reservoir Knockholt New South Service Reservoir	RSR0295 RSR0296
West Wickham New East Service Reservoir West Wickham New West Service Reservoir	RSR0053 RSR0305
Farborough Community Supply System	YTMS1192
Knockholt Community Supply System	YTMS1206
Bromley Common, Bromley Inset (LNW) (TW Community: Farnborough) Supply System	YTMS3000
Westerham Community Supply System	YTMS1231
Addington Community Supply System	YTMS1167
Russell Hill Community Supply System	YTMS1218

Table 1: List of assets affected and associated reference numbers

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 10 and 11 August 2021, which states that there is or has been a significant risk of supplying water from assets in the Farnborough Service Reservoir Chain listed above (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 bacteriological risk.	Chlorine Biological Inorganic	Multiple risk assessment reports (Annex 1) e.g. for Farnborough A: TMS-5-RSR0328-HEID065-RSR0328-H047 TMS-5-RSR0328-HEID065-RSR0328-H046 TMS-5-RSR0328-HEID065-RSR0328-H027

Table 2: 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. Enhanced sampling (in addition to routine regulatory sampling) for coliform bacteria, E. coli, colony counts and chlorine (free and total) at a frequency of twice a week from each service reservoir cell in Farnborough Reservoir chain.
   Date: Ongoing for the duration of this Notice.
2. Regular reviews (London Water Quality turnover assessment meetings) of chlorine residuals and turnover for each cell in the Farnborough Reservoir chain that is listed.
   Date: Ongoing for the duration of this Notice.
3. 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.

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

Initial Improvement Measures and Data Collection

1. Carry out a review of all sample points and relevant instrumentation across the Farnborough Service Reservoir supply systems to ensure representative monitoring is in place. Specifically, review the sufficiency of chlorine monitoring and, where required for modelling and performance data, install and commission online chlorine monitor(s) across the Farnborough Service Reservoir chain. Implement any necessary improvements to sampling and instrumentation as identified.
   Date: Complete (30 September 2022).
2. Conduct a trial reconfiguration of mains at Farnborough Cell A so that the cell can operate with separate inlet and outlet mains. Monitor the impact at Farnborough and across the supply chain.
   Date: Complete (30 September 2022).
3. For all cells in the Farnborough Service Reservoir chain:
   1. Confirm and verify the key valve (in terms of turnover) positioning (and appropriateness thereof) and operability.
   2. Carry out inspections of the critical air valves immediately upstream of each service reservoir in the Farnborough Service Reservoir Chain.
   3. Investigate any network dead legs, across the Farnborough Service Reservoir Chain, and associated zones, that may have an impact on the quality at the service reservoirs.
   4. Identify any remedial work or additional control measures required to address any risks identified under (b)(3)(a-c) above. Develop a plan including timeframes to complete any work required.

Date: Complete (31 March 2022).

4. Implement the plan developed in (b)(3)(d) above, and complete any work required.
   Date: Complete (30 September 2022).

Supply System Review

5. Complete a detailed, holistic review of the inadequate turnover and low chlorine residuals across Farnborough Service Reservoir Chain, including:
   1. Review the pumping and control strategy of the Water Treatment Works supplying the service reservoir chain (including the main from Knockholt to Betsoms Hill) to assess optimum operational regime for adequate turnover, taking into account pressure management as well as water quality requirements.
   2. Review the blend between chloraminated and chlorinated Water Treatment Works supplying the Farnborough Service Reservoir Chain to assess the extent of the risk the arrangement may contribute to low chlorine residuals.
   3. Review water quality trends (Free and Total chlorine) in Farnborough Service Reservoir Chain (cells and associated zones).
   4. Investigate any leakage, pressure management issues and flow changes across the Farnborough Service Reservoir Chain, and associated zones, to assess risk of ingress at different operating configurations.
      Date: Complete (31 March 2023).
6. Identify any remedial work or additional control measures for the Farnborough Service Reservoir Chain required to address any risks identified through the holistic review measure (b)(5) above. Develop a plan including timeframes to complete any work required.
   Date: Complete (30 September 2023).
7. Provide the high-level design of the chosen solution identified in measure (b)(6)
   Date: 31 December 2024.
8. Implement the chosen solution, identified in measure (b)(7).
   Date: TBC

Individual Reservoir Review

9. Review the operational arrangements including the inlet and outlet arrangements for each cell in the Farnborough Service Reservoir chain and identify any improvements, if required, and consider the implications on representativeness of sampling arrangements.
   Date: Complete (31 March 2023).
10. Identify and design any appropriate mitigation(s) for the specific cells to address any risks identified through measure (b)(8) above.
    Date: Complete (30 September 2023).
11. Review the risks to individual service reservoirs in the Farnborough Chain, following installation of the chosen solution identified and implemented in measures (b)(7) and b(8) respectively, and confirm if any further mitigation is required.
    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 sections (a) and (b).
   Date: Complete (30 November 2021).
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 service reservoirs in the Farnborough Chain, 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 the outcome of the sample point review across the supply system and implementation (and commissioning) of improvements, including any online chlorine monitoring requirements.
   Date: Complete (21 October 2022).
3. Provide a report on the outcome of the trial reconfiguration at Farnborough Cell A, including an assessment of the effectiveness of the reconfiguration on improving turnover on the chlorine residuals in Cell A. Confirm whether a separate inlet/outlet arrangement will become a permanent mitigation measure.
   Date: Complete (21 October 2022).
4. Provide a report on the outcomes of all steps in measure (b)(3), stating any required mitigation measures and the plan (including timeframes) to complete the measures.
   Date: Complete (26 April 2022).
5. Confirm implementation of any required mitigation as specified in measure (b)(4).
   Date: Complete (21 October 2022).
6. Confirm the outcomes of the holistic review of the Farnborough Service Reservoir Chain as specified in (b)(5) and report the mitigations that have been identified as a result of the review (b)(6), including a plan with proposed timeframes to complete any work required.
   Date: Complete (31 October 2023).
7. Provide a report on the high-level design, as required in measure (b)(7).
   Date: 31 January 2025.
8. Provide a report confirming the installation of the chosen solution, as required by measure (b)(8).
   Date: TBC
9. Provide a report on the outcomes of the individual reservoir review as specified in (b)(8), including the mitigations that have been identified as a result of the review (b)(9), including a plan with timeframes to complete any work required.
   Date: Complete (31 October 2023).
10. Provide a report on the individual service reservoirs, following installation of the chosen solution, as specified in measure (b)(11).
    Date: TBC.
11. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete (31 December 2021).
12. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision.
13. 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.
14. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: TBC.

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).

Signed

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
13 September 2024
Reference: TMS-2021-00002 v3