Southern Water Services Limited – Network Storage Asset Health Replacements

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

Reference: SRN-2026-00002

Version Number: v1

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Southern Water Services Limited, with registered number 02366670 (hereinafter called ‘the company’).

Assets Affected:

All Southern assets listed in Appendix A, and the associated supply systems.

Details of this Notice:

The Drinking Water Inspectorate (‘the Inspectorate’) has received various regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the company dated 13 October 2025 and 13 January 2026, which states that there is or has been a significant risk of supplying water from the sites listed in the Appendices (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
Structural integrity of asset at risk	No Supply	137252
Insufficient water supply to downstream consumers	No Supply	137253
Microbiological contamination due to ingress	Total Coliforms	35295
Microbiological contamination due to ingress	E. coli	35296
Microbiological contamination due to ingress	Clostridium Perfringens	35293
Microbiological contamination due to ingress	Enterococci	35297

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.

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:

Undertake scheduled Southern Water operator site inspections of treated water storage assets.
Date: Ongoing for the duration of this Notice.
Undertake grounds maintenance at the standard frequency.
Date: Ongoing for the duration of this Notice.
Internally inspect treated water storage assets according to Southern Waters current reservoir programme.
Date: Ongoing for the duration of this Notice.
Carryout maintenance tasks at the water storage assets in accordance with Southern Water standards.
Date: Ongoing for the duration of this Notice.
Sample treated water storage assets to check compliance at the frequency defined by the annual Southern Water Sampling Programme.
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:

Confirm the replacement treated water storage tanks be to constructed in AMP8 following Ofwat’s final determination and detail any that will be carried forward for replacement in AMP9. Update the Appendix A accordingly.
Date: 31 March 2027.
Provide a detailed design for the AMP8 replacement treated water storage tanks for assets listed in Appendix A.
Date: 31 October 2027.
Complete the construction and commissioning of the AMP8 replacement treated water storage tanks for assets listed in Appendix A.
Date: 31 March 2031.

(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: 31 December 2026
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 the sites listed in the Appendices, or not to so supply unless the specified conditions below are satisfied:

(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 an annual report on progress with b milestone actions.
Date: 30 April each year.
Provide a report confirming the outcome of Ofwat’s final asset health determination and how this impacts the scheduling of the treated water storage tanks to be replaced in AMP8, identifying those to be completed in AMP8 and those carried forward to AMP9 for completion. Provide an updated Appendix A where required identifying those treated water storage tanks to be replaced in AMP8 and AMP9.
Date: 30 April 2027.
Provide a report on the detailed design for the replacement treated water storage tanks for assets listed for completion in AMP8 in Appendix A.
Date: 30 November 2027.
Provide a report on the completion of the construction and commissioning of the AMP8 replacement treated water storage tanks for assets listed in Appendix A.
Date: 30 April 2031.
Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: 31 January 2026
Submit any revisions of the audit strategy produced under measure (c)2.
Date: Within 1 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: 30 April 2032.

Further Details of this Notice:

Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
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.
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 October 2026
Reference: SRN-2026-00002

Appendix A

Asset ref	Asset name	Supply system ref	Supply system name
RH006	Beacon Hill Woodnesborough WSR North	Y005	Kingsclere
RH007	Beacon Hill Woodnesborough WSR South	Y005	Kingsclere
RH045	Sidown Hill WSR North	Y005	Kingsclere
RH044	Sidown Hill WSR South	Y005	Kingsclere
RK063	Southdown Halfway Houses WSR North	Y010	Thanet

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