Notice of regulation: South West Water Limited – St Agnes Water Quality Improvements

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

Reference: ISC-2021-00006

Version Number: 5

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): South West Water Limited, with registered number 02366665 (hereinafter called ‘the Company’).

Assets Affected:

  • St Agnes Supply System YIOS4
  • Plump WTW T0001F
  • Tommy’s WTW T0002F

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 09 April 2021, which states that there is or has been a significant risk of supplying water from water treatment works (and associated assets as applicable) on St Agnes Island 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

Potential risks to drinking water quality and non-compliance with the Water Supply (Water Quality) Regulations.



Total coliforms


E. coli




C. perfringens






Indicative Dose






Gross Alpha


Gross Beta


















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.
  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.


(a) To maintain the following measures for the period specified in each case:

  1. Continue the current investigational water quality monitoring programme to support regulation 27 risk assessment and verify the current operational practice and performance.
    Date: Ongoing for the duration of this Notice
  2. Continue to operate the existing assets and supply systems in accordance with operating procedures.
    Date: Ongoing for the duration of this Notice
  3. Maintain current advice to consumers that water supplied to this supply zone should not be used in infant feed and formulas, until such time that the treatment process is capable of reducing the concentration of chloride to below that of the prescribed concentration set out in the Regulations.
    Date: Ongoing for the duration of this Notice
  4. Maintain contingency plans to protect human health in the event of a risk associated with 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. Investigate the raw water quality and existing treatment processes available on St Agnes to confirm the risks and parameters that are currently unmitigated or require further mitigation to be included in this Notice.
    Date: Complete
  2. Identify and implement short term mitigation(s) as soon as reasonably practicable, based on suitable risk assessment where any hazards that have the potential to contribute to regulation 4 breaches are identified through the completion of measure (b)1.
    Date: 30 September 2023
  3. Following the completion of step (b)1., review the existing treatment processes and control measures on St Agnes Island to ascertain if current treatment is capable of the removal of the parameters listed in Section 2 of this Notice.
    Date: 31 March 2024
  4. Following the review in step (b)3., if the existing treatment and control measures are not capable of mitigating the risks associated with the hazards listed in section 2 of this notice, design additional treatment stages and control measures required for effective mitigation of the risks associated with these listed hazards.
    Date: 30 June 2024
  5. Review and update the regulatory sampling facilities on the island to be in line with the company standard.
    Date: 31 December 2024
  6. Complete the installation and commissioning of the required control measures identified in (b)4., to enable full operational use of the improved supply system.
    Date: 31 March 2025
  7. Update the site policies and procedures to reflect the changes made to the supply system, including providing any relevant additional training to staff, based on the changes made.
    Date: 31 March 2025

(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 water treatment works and associated assets on St Agnes Island, 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 completion of the investigation in step (b)1. and any further parameters to be added to Section 2 of this Notice.
    Date: Complete
  3. Confirm the implementation of any short-term mitigation(s) required as specified in measure (b)2.
    Date: 31 October 2023
  4. Provide a report on the chosen design of treatment process and any additional control measures required, as specified in step (b)4.
    Date: 31 July 2024
  5. Confirm the upgrade of all regulatory sampling facilities on the island to be in line with the company standard, as specified in measure (b)5.
    Date: 31 January 2025
  6. Confirm completion of the installation and commissioning of the required treatment stages and control measures, as described in (b)6. Provide evidence of the updated site policies and procedures and any relevant additional training delivered to staff, as specified in (b)7.
    Date: 30 April 2025
  7. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete
  8. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  9. 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
  10. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 April 2026

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).


Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
23 January 2023
Reference: ISC-2021-00006 (V5)

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