Sutton and East Surrey Water Plc – AMP8 Cheam Cryptosporidium

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

Reference: SES-2023-00006

Version Number: 1

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Sutton and East Surrey Water Plc, with registered number 02447875 (hereinafter called ‘the Company’).

Assets Affected:

  • TSCTW – Cheam Water Treatment Works
  • Y20 – North Looe Supply System (ZL20 North Looe Water Supply Zone)
  • Y21 – Langley Park Sutton Supply System (ZL21 Langley Park Sutton Water Supply Zone)
  • Y22 – Langley Park Morden Supply System (ZL22 Langley Park Morden Water Supply Zone)
  • Y19 – Nork Supply System (ZL19 Nork Water Supply Zone)
  • Y17 – Burgh Heath & Margery Supply System (ZL17 Burgh Heath & Margery Water Supply Zone)

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 4 October 2023, which states that there is or has been a significant risk of supplying water from Cheam water 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

Hazard I D

WS(WQ) Regs Reg 4 Wholesomeness parameter



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. Maintain monitoring for Cryptosporidium from the three blended raw water sources (Ref. ASCBM, ASCEB, ASCNM) supplying Cheam treatment works through continuous monitoring and weekly changeover of filtramax cartridges.
    Date: Ongoing for the duration of this Notice
  2. Maintain proactive external site inspections, grounds maintenance, site security and asset maintenance and keep appropriate records for raw water sources supplying Cheam treatment works, and Cheam Treatment works.
    Date: Ongoing for the duration of this Notice
  3. Maintain appropriate contingency plans for Cheam treatment works (including liaison with relevant stakeholders as appropriate) to ensure drinking water quality and sufficiency can be maintained 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. Design a solution to address the risk of Cryptosporidium identified through the completion of the PR24 submission.
    Date: 31 March 2027
  2. Complete the construction, installation and commissioning of the ultra violet (UV) treatment process at Cheam treatment works. Commissioning must include the following to account for the changes made:
  • Full integration of any new processes into the site control and monitoring systems;
  • Updating of the Site-Specific Disinfection Policy and any associated site specific procedures;
  • Updating of the Site Operating Manual;
  • Provision of adequate training to all relevant personnel on the operation, repair and maintenance of the chosen installed process solution and the revised procedures, policies and manual.

Date: 31 December 2028

(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: 31 May 2024
  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 Cheam 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. Submit a report outlining the Company’s chosen solution (measure (b)1).
    Date: 30 April 2027
  3. Confirm the measures implemented under measure (b)2 and confirm implementation and commissioning of the chosen solution (measure (b)2)
    Date: 31 January 2029
  4. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: 30 June 2024
  5. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  6. 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
  7. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 31 January 2030

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
15 March 2024
Reference: SES-2023-00006

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