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

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

Reference: TMS-2024-00007

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:

Asset Name	Reference
Bowsey Hill North SR	RSR7160
Bowsey Hill South SR	RSR7161
Henley Supply System	YTMS1200

Table 1: List of assets affected and associated reference numbers

Details of this Notice:

The Drinking Water Inspectorate (‘the Inspectorate’) has received regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 17 July 2023, which state that there is or has been a significant risk of supplying water from Bowsey Hill Service Reservoir (and associated assets as applicable) that could constitute a potential danger to human health or could be unwholesome.
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-RSR7160-MDCT004-RSR7160-C001 and TMS-5-RSR7160-MDCT004-RSR7161-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-RSR7160-MDCT005-RSR7160-C002 and TMS-5-RSR7160-MDCT005-RSR7161-C002
Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.	Enterococci	TMS-5-RSR7160-MDCT006-RSR7160-C003 and TMS-5-RSR7160-MDCT006-RSR7161-C003
Potential risks from storage of water in tanks; including contamination from ingress or egress, and microbiological re-growth.	Colony Counts	TMS-5-RSR7160-MDCT001-RSR7160-C007 and TMS-5-RSR7160-MDCT001-RSR7161-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-RSR7160-HEID067-RSR7160-H047 and TMS-5-RSR7160-HEID067-RSR7161-H047
Contamination	Non-compliance with reservoir/ tanks inspection programme	TMS-5-RSR7160-HEID094-RSR7160-H062 and TMS-5-RSR7160-HEID094-RSR7161-H062
Contamination	Supply resilience	TMS-5-RSR7160-HEID093-RSR7160-H047 and TMS-5-RSR7160-HEID093-RSR7161-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.

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:

Operate Bowsey Hill Service Reservoir in accordance with current company policy, standards and procedures, that align to recognised standards of good practice.
Date: Ongoing for the duration of this Notice.
Maintain risk-based enhanced (in addition to routine regulatory sampling) sampling for Bowsey Hill Service Reservoir. This must include, as a minimum, colony counts, E. coli and coliforms.
Date: Ongoing for the duration of this Notice.
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.
Maintain appropriate contingency plans (including liaison with relevant stakeholders as appropriate) to protect human health.
Date: Ongoing for the duration of this Notice.
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:

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 Bowsey Hill Service Reservoir.
Date: 31 July 2024.
Complete the required enabling works identified under measure (b)1.
Date: 31 December 2030.
Complete the physical internal inspection of Bowsey Hill Service Reservoir.
Date: 30 June 2031.
Outline the scope of any required work identified by the internal inspection and further milestones as a result of any remedial work.
Date: 31 August 2031.
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:

Define an audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
Date: 30 September 2024.
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 Bowsey Hill Service Reservoir North or South, or not to so supply unless the specified conditions below are satisfied:

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:

Provide a progress report annually.
Date: by 31 January each year.
Provide the plan, including timeframes, of the enabling works required to remove Bowsey Hill Service Reservoir from supply for a physical internal inspection, clean, flood test and completion of any required remedial work.
Date: 31 August 2024.
Confirm completion of the enabling works required.
Date: 31 January 2031.
Provide the inspection report and confirm the scope of remedial work required and further milestones as a result of any remedial work.
Date: 30 November 2031.
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.
Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: 31 October 2024.
Submit any revisions of the audit strategy produced under measure (c)2.
Date: Within one month of a revision.
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.
Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
Date: 31 December 2032

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
10 July 2024.
Reference: TMS-2024-00007 v1

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