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Portsmouth Water Limited – Slindon Treatment Works, Risk to Disinfection

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

Reference: PRT-2020-00008

Version Number: 4

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Portsmouth Water Limited, with registered number 02536455 (hereinafter called ‘the Company’).

Assets Affected:

  • TSLN – Slindon Treatment Work

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 20 October 2017, which states that there is or has been a significant risk of supplying water from Slindon Treatment Works (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

Failure to meet requirements of regulation 26, inadequate disinfection, due to a failure to demonstrate that disinfection contact time is met under all conditions.

Microbiological

Failure to demonstrate chlorine contact time within the contact main.

Microbiological

Disinfection – Inadequate disinfection (failure to meet CT time) – microbiological and viruses.

Microbiological

Table 1: Table of the hazards, hazardous events, and/or parameters covered by this Notice, including the Hazard 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 a treatment process which meets the requirements of regulation 26 in full to disinfect the water at all times and under all flow conditions.
    Date: Ongoing for the duration of this Notice
  2. Continuously review all critical control points and mitigation measures with a view to updating the Notice with additional measures where required. Ensure that any new risk identified is assessed in accordance with the Company’s Drinking Water Safety Plan (DWSP) methodology.
    Date: Ongoing for the duration of this Notice
  3. Operate all processes within defined operating ranges, with appropriate triggers, responses and contingency procedures.
    Date: Ongoing for the duration of this Notice
  4. Ensure the works control and shutdown system is operational and that monitors are calibrated at the predefined frequencies.
    Date: Ongoing for the duration of this Notice
  5. Continuous monitoring to ensure that water being presented for disinfection is of the required standard to achieve disinfection and to verify that disinfection is taking place and is effective.
    Date: Ongoing for the duration of this Notice
  6. Take action to prevent water leaving the treatment works when monitoring indicates that the water quality falls outside target range and that disinfection requirements are not met. The Company must take appropriate action to protect human health.
    Date: Ongoing for the duration of this Notice
  7. Maintain documented procedures for the escalation and investigation of any deviation from expected results or consumer complaints.
    Date: Ongoing for the duration of this Notice
  8. Take all reasonable operational steps (and continue to enhance the effectiveness) to ensure that water that is not compliant with the requirements of regulations 4 and 26 is prevented from entering supply.
    Date: Ongoing for the duration of this Notice
  9. Enhanced operational water quality monitoring to validate and verify the quality of water entering supply.
    Date: Ongoing for the duration of this Notice
  10. Maintain enhanced and appropriate monitoring for Cryptosporidium.
    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. Complete the construction, installation (or modification of the existing) and commissioning of the chosen disinfection and treatment process (designed under Notice PRT4087, which this Notice replaces). Commissioning must include the following to account for the changes made:
  • Updating of the Site-Specific Disinfection Policy and any associated site-specific procedures.
    Date: Complete
  • Updating of the Site Operating Manual and removal of all out of date material from circulation.
    Date: Complete
  • Provision of adequate training to operators on the chosen solution installed (or modified) and site operating manual under this measure.
    Date: Complete
  1. Carry out continuous monitoring for Cryptosporidium and enhanced frequency (weekly sampling for microbiological parameters) monitoring for faecal indicator organisms for a minimum of 2 years to verify the Company’s catchment risk assessment and review the capabilities of the existing treatment in place.
    Date: 31 May 2026
  2. Design a disinfection and treatment process (or modify the existing process) that addresses any unmitigated risks identified through the completion of the gap analysis required under measure (b)2.
    Date: 31 December 2026 (if measure is required, based on the outcome of b(2)).
  3. Complete the construction, installation (or modify the existing) and commissioning of the chosen disinfection and treatment process defined by (b)3 Commissioning must include the following to account for the changes made:
  • Updating of the Site-Specific Disinfection Policy and any associated site-specific procedures.
    Date: 31 March 2030 (if measure is required, based on the outcome of b(2)).
  • Updating of the Site Operating Manual and removal of all out of date material from circulation.
    Date: 31 March 2030 (if measure is required, based on the outcome of b(2)).
  • Provision of adequate training to operators on the chosen solution installed (or modified) and site operating manual under this measure.
    Date: 31 March 2030 (if measure is required, based on the outcome of b(2)).

(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 Slindon Water Treatment Works, 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. Confirmation of completion of measure (b)1
    Date: Complete
  3. Submit a report to confirm details of the strategy for auditing the effectiveness of the measures as specified in (c)1.
    Date: Complete
  4. Submit a report summarising the performance of the solution, installed under measure (b)1, over the year since its installation.
    Date: 30 June 2025.
  5. Submit a report outlining the findings of the gap analysis for the company’s catchment risk assessments.
    Date: Complete
  6. Submit a report detailing the results of the enhanced monitoring to verify the Company’s risk assessment, and the review of the capabilities of the existing treatment based on the verified catchment risk assessment using a minimum of 2 years enhanced monitoring data. Confirm the projected completion dates measures (b)3 and (b)4.
    Date: 30 June 2026
  7. Submit a report outlining the Company’s chosen treatment design specification as defined by measure (b)3, accompanied by an updated audit strategy.
    Date: 31 January 2027 (if measure is required, based on the outcome of b(2)).
  8. Submit a report documenting the completion of measure (b)4.
    Date: 30 April 2030 (if measure is required, based on the outcome of b(2)).
  9. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  10. 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
  11. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 April 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

Laura Moss
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
27 February 2024
Reference: PRT-2020-00008 V4

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