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Thames Water Utilities Limited – Ashbury Hill Service Reservoir Inspect and Clean

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

Reference: TMS-2022-00010

Version Number: 2

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

Ashbury Hill Service Reservoir

RSR0214

Ashbury Community Supply System

YTMS1168

Table 1: List of assets affected and associated reference numbers

Details of this Notice:

  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received a set of regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 24 May 2022, 25 May 2022, 07 June 2022 and 14 June 2022, which state that there is or has been a significant risk of supplying water from Ashbury Hill Service Reservoir (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

Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.

Coliform bacteria

TMS-5-RSR0214-MDCT004-RSR0214-C001

Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.

Escherichia coli (E. coli)

TMS-5-RSR0214-MDCT005-RSR0214-C002

Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.

Enterococci

TMS-5-RSR0214-MDCT006-RSR0214-C003

Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.

Colony Counts

TMS-5-RSR0214-MDCT001-RSR0214-C007

Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.

Chlorine (chlorine free and total)

TMS-5-RSR0214-MDCT145-RSR0214-H047 and TMS-5-RSR0214-MDCT146-RSR0214-H047

Contamination

Access to water space/ ingress routes

TMS-5-RSR0214-HEID068-RSR0214-H062

Contamination

Non-compliance with reservoir/ tanks inspection programme

TMS-5-RSR0214-HEID094-RSR0214-H062

Contamination

Supply resilience

TMS-5-RSR0214-HEID093-RSR0214-H062

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.
  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. Operate Ashbury Hill Service Reservoir in accordance with company policy, standards and procedures, that align to recognised standards of good practice.
    Date: Ongoing for the duration of this Notice.
  2. Maintain risk-based enhanced (in addition to routine regulatory sampling) sampling for Ashbury Hill Service Reservoir. This must include, as a minimum, colony counts, E. coli and coliforms.
    Date: Ongoing for the duration of this Notice.
  3. Maintain proactive external site inspections, grounds maintenance, site security and asset maintenance. This must include periodic inspections of hatches, seals, redundant assets, sample taps, overflows, washouts and air valves.
    Date: Ongoing for the duration of this Notice.
  4. Maintain appropriate contingency plans (including liaison with relevant stakeholders as appropriate) to protect human health.
    Date: Ongoing for the duration of this Notice.
  5. Keep under review the service reservoir’s residual chlorine concentrations to ensure appropriate set points and trigger values are in place to prevent a deterioration of drinking water quality.
    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. Develop a plan for the enabling works required to allow the physical internal inspection, clean, flood test and completion of any required remedial work of Ashbury Hill Service Reservoir.
    Date: Complete
  2. Complete the required enabling works identified under measure (b)1.
    Date: 31 December 2029
  3. Complete the physical internal inspection of Ashbury Hill Service Reservoir.
    Date: 30 September 2030
  4. Outline the scope of any required work identified by the internal inspection and further milestones as a result of any remedial work.
    Date: 31 October 2030
  5. In the eventuality that a risk of active ingress or egress is identified:
  • Implement immediate mitigation measures to ensure public health is protected; and
  • Review the plan developed under (b)1 and the associated dates for delivery, in light of the identified risk
    Date: Ongoing for the duration of this Notice.

(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 Ashbury Hill Service Reservoir, 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 the plan, including timeframes, of the enabling works required to remove Ashbury Hill Service Reservoir from supply for a physical internal inspection, clean, flood test and completion of any required remedial work.
    Date: Complete
  3. Confirm completion of the enabling works required.
    Date: 31 January 2030
  4. Provide the inspection report and confirm the scope and date of remedial work required and further milestones as a result of any remedial work.
    Date: 30 November 2030
  5. Report any measures taken to protect human health and submit the reviewed plan with dates, as required under measure (b)5 where ingress or egress risk is identified.
    Date: Ongoing for the duration of the Notice. Report to be provided within one month of the risk being identified.
  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 one 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: 30 November 2031

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
14 November 2023
Reference: TMS-2022-00010 v2

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