Notice of Regulation: London Slow Sand Filter Works

THE WATER SUPPLY (WATER QUALITY) REGULATIONS 2016 (AS AMENDED)

NOTICE UNDER REGULATION 28(4)

THAMES WATER UTILITIES LTD: London Slow Sand Filter Works

DWI Reference number: TMS3966 V2

Site Name

Site Reference

Ashford Common

T01S.008

T01S.009

T01S.001

Coppermills

T02S.001

Hampton

T01S.010

T01S.011

T01S.012

Kempton Park

T01S.004

THE SECRETARY OF STATE:

  1. has received a report from Thames Water Utilities Ltd (the “Company”) dated 29 March 2018 (the “Report”) which states that there is or has been a significant risk of supplying water from Ashford Common, Coppermills, Hampton and Kempton Park water treatment works that could constitute a potential danger to human health and could be unwholesome.
  2. GIVES NOTICE to the Company under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended) that it must satisfy the following requirements:

For risks associated with:

  • Failure to comply with regulation 26 and regulation 4
  • Failure of the slow sand filtration process
  • Presence of Cryptosporidium in final water
  • Biological hazards (including E. coli, Total Coliforms, Enterococci, Clostridium)

Requirements

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

To ensure that wholesome water is supplied to consumers at all times, in accordance with the requirements of regulation 4, maintain existing operational measures which must include the following at all sites covered by this Notice:
Date: With immediate effect and ongoing for the duration of the Notice.

  1. Continuous sampling for Cryptosporidium at a suitable sampling point downstream of slow sand filtration and other processes important for the removal of particulate material.
  2. An appropriate operational sampling regime for Cryptosporidium, turbidity, microbiological faecal indicators and other relevant parameters in: the raw water source(s) supplying the water treatment works; at other sampling points within the process; and in the final treated water.
  3. Operation of all processes within defined operating ranges with appropriate triggers, responses and contingency procedures.
  4. Ensure the works control and shutdown system is operational and that monitors are calibrated at the predefined frequencies.
  5. Continuously review all critical control points and mitigation measures for the duration of this Notice 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.
  6. Water quality response procedures for: investigation of contraventions including process optimisation and reporting; consumer complaints procedures; event response procedures for event actions; and notification criteria.
  7. Up-to-date Site Operating Manual (SOM), defining normal operating ranges, triggers, response and contingency procedures, with controlled update and review programmes. Internal waiver process is followed where deviation from SOM is required.
  8. Up-to-date and subject to continuous review, site specific disinfection policy, which identifies clearly and unequivocally how disinfection is achieved at the works.
  9. Maintain contingency plans to protect human health in the event of a risk to human health associated with drinking water quality, which should include liaison with local authorities and Public Health England to agree any actions needed to protect human health and issuing of advice to consumers, where required.
  10. In accordance with the requirements of regulation 27(3), continuously review and revise as necessary the regulation 27 risk assessments and submit revised regulation 28 reports to the Inspectorate as necessary, in accordance with the published procedure.
  11. Carry out and record daily inspections of slow sand filters for animal ingress.
  12. Promptly report any animal ingress into any exposed (open-air) treatment stages, including slow sand filters, to appropriate competent Water Quality staff in accordance with the Company’s procedure.
  13. Carry out appropriate analysis and disposal of any animal carcasses in accordance with the Company’s procedure.
  14. Enhanced monitoring of slow sand filter beds’ flow rate changes and associated alarms to ensure flow rates are properly managed to prevent particle detachment within the beds.
  15. Appropriate slow sand filter flow control using the outlet valve to ensure the rate of change does not exceed predetermined limits.
  16. Trained and competent operational personnel to follow the Company’s procedure when returning slow sand filters to supply.
  17. Complete monthly rapid gravity primary filter media depth inspections.
  18. Ordering of liquid oxygen in a timely fashion to avoid unnecessary ozone plant shutdowns due to a lack of oxygen.

(b) to implement the following measures, by the dates specified:

  1. Complete the Hazard Reviews required under regulation 28(4) Notice TMS3952 which must include a review of the following in relation to all slow sand filters:
    Date: 31 December 2019
    • The age and the condition;
    • Ability to adequately remove the maximum raw water quality challenge at all times;
    • Operating regime for the slow sand filters; and
    • Procedures in place for optimising the duration in service, empty bed contact time and hydraulic management.
  2. Review and update the Company’s Operating Standard for slow sand filters.
    Date: 31 December 2018
  3. Review and implement an appropriate riskbased maintenance programme for all slow sand filters, which includes a documented frequency for underdrain inspections as well as filter media inspection and replacement.
    Date: 31 March 2019
    • a) Conduct a critical review on how the risk from animal (including birds) access to the site and critical treatment stages, as well as excessive vegetation growth on treated water structures, can be minimised. This review is to include the appropriateness of daily visual monitoring checks for slow sand filters.
      Date: 31 December 2018
    • b) Identify any measures required to address the findings of the critical review completed under measure (b)4.a) above. The identified measures must include the implementation of a documented procedure to limit animal ingress to critical treatment stages and to prevent excessive vegetation growth on treated water structures.
      Date: 31 March 2019
    • c) Implement the measures identified under (b)4.b) above.
      Date: 01 June 2020
  4. Erect appropriate barriers around slow sand filters to prevent access by mammalian wildlife.
    Date: 31 December 2019
  5. Install and commission continuous turbidity monitoring on the outlets of each individual slow sand filter at Ashford Common, Hampton and Kempton Park water treatment works. Ensure that the analytical instruments and associated equipment installed incorporate appropriate alarms and failsafe measures, that are linked to the treatment works’ control system, to prevent inadequately disinfected water from entering supply.
    Date: – Ashford 31 March 2020
    Date: – Hampton 31 March 2020
    Date: – Kempton 31 March 2021
    • a) Install and commission continuous turbidity monitoring on the outlets of each individual slow sand filter at Coppermills water treatment works.
      Date: 30 September 2019
    • b) Ensure that the analytical instruments and associated equipment, installed under measure (b)7.a) above, incorporate appropriate alarms and failsafe measures that are linked to the treatment works’ control system, to prevent inadequately disinfected from water entering supply.
      Date: 31 March 2021
    • a) Develop a Rapid Gravity Primary Filters Action Plan to ensure their effective operation, including a review of:
      Date: 31 March 2019
      • Backwash stages and timings;
      • Compliance with media depth and characteristics requirements;
      • Current valve performance; and
      • Control (signals, flow rate changes and backwash hydraulics).
    • b) Implement the recommendations of the Rapid Gravity Primary Filters Action Plan completed under (b)8.a).
      Date: 01 August 2020
  6. Review and update the Company’s Operating Standard for rapid gravity primary filters.
    Date: 31 December 2018
    • a) Review and, where necessary, revise the training provided on the operation, maintenance and monitoring of slow sand filters and rapid gravity primary filters following completion of measures (b)2. and 9.
      Date: 30 June 2019
    • b) Implement a programme to re-train all relevant personnel as applicable following the completion of (b)10.a) above.
      Date: 31 December 2019

(c) to audit whether the measures have been effective by the following means:

  1. Define a strategy for auditing the effectiveness of the measures being delivered in section (b). This must:
    Date: 25 July 2020
    • Include the design and implementation of a regular programme of audit and review (incorporating any lesson learnt or improvements made through implementation of the measures in section (b));
    • Permit continuous learning and development beyond the life of this Notice; and
    • Include the transfer of any lessons learnt from the delivery of this Notice to the Company’s other slow sand filter sites as appropriate.
  2. Implement the audit strategy outlined in (c)1. above.
    Date: Until revocation of this Notice

(d) not to supply water for regulation 4(1) purposes from Ashford Common, Coppermills, Hampton and Kempton Park water treatment works unless the conditions specified below are satisfied:

  1. n/a

(e) to provide the following information in the time and manner specified below to enable monitoring of progress towards the mitigation of the risk of supplying water that would constitute a potential danger to human health:

  1. i. Provide a progress report annually by 31 January and against the following milestones:
    • Report to confirm details of the strategy for auditing the effectiveness of the measures as specified in section (c).
      Date: 25 July 2020
    • Outcome of the reviews completed under measure (b)2. and (b)9.
      Date: 31 January 2019
    • Outline of the reviewed and implemented programme completed under measure (b)3.
      Date: 30 April 2019
    • Report outlining the findings of the critical review completed under (b)4.a) and the measures to be taken to address any deficiencies identified (as required under measure (b)4.b)) and their proposed timescales for delivery.
      Date: 30 April 2019
    • Confirmation of the completion of any measures required under measure (b)4.c).
      Date: 01 August 2020
    • Confirmation of the installation of barriers around slow sand filters as required under measure (b)5.
      Date: 31 January 2020
    • Confirmation of the completion of measure (b)6 at Ashford Common, Hampton and Kempton Park.
      Date: – Ashford 30 April 2020
      Date: – Hampton 30 April 2020
      Date: – Kempton 30 April 2021
    • Confirmation of installation and commissioning of continuous turbidity monitors at Coppermills water treatment works as required under measure (b)7.a).
      Date: 31 October 2019
    • Confirmation of the completion of measure (b)7.b).
      Date: 30 April 2021
    • Outline of the action plan completed under measure (b)8.a) and the resulting proposed timescales for delivery of any required improvements.
      Date: 30 April 2019
    • Confirmation of the implementation of the actions identified in the Rapid Gravity Primary Filters Action Plan as required by measure (b)8.b).
      Date: 01 October 2020
    • Outcome of the review completed under (b)10.a).
      Date: 31 July 2019
    • Confirmation of the completion of measure (b)10.b).
      Date: 31 January 2020
  2. Review the risk assessments for Ashford Common, Coppermills, Hampton and Kempton Park water treatment works as required by regulation 27(3) and subsequently submit revised regulation 28 reports accompanied by signed board level declarations.
    Date: From time to time and 2 months after the completion of all measures in section (b)
  3. Submit a satisfactory completion report.
    Date: 13 months after the completion of all measures in section (b)

Failure by the Company to comply with this Notice may result in enforcement proceedings under section 18 of the Act.


Signed by authority of the Secretary of State
Laura Moss
Deputy Chief Inspector
25 June 2020
DWI ref: TMS3966
Version 2

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