South West Water Limited – Alderney Water Treatment Works, Disinfection Improvements

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

Reference: SWB-2020-00007

Version Number: 2

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:

• Alderney WTW (T9100F7, T9100F8)
• Alderney Supply System (Y9100)
• Longham Lakes (A9100R2, A9100R3 and A9100R1)
• Alderney North Supply Zone (ZBW3)
• Alderney South Supply Zone (ZBW1)
• Alderney East Supply Zone (ZBW2)
• Alderney West Supply Zone (ZBW11)

Details of this Notice:

1. The Drinking Water Inspectorate (‘the Inspectorate’) has received multiple regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 20 October 2020 (as well as, 18 October 2019; 22 January 2020; 13, 14 and 18 October; and 01 December 2020), which state that there is or has been a significant risk of supplying water from Alderney 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 (multiple hazards including but not limited to the following, by way of example):
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Colour	8181, 2935
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Total algae	7779, 2921
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Taste and odour	7963, 7964, 2938, 2939
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Total organic carbon (including dissolved organic carbon)	7988, 2931
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Disinfection by-products, including trihalomethanes	7783, 2925
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Pesticides	7871, 2958
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Oil / fuel	7781, 2923
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Cryptosporidium	7837, 3038
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Colony counts	7788, 2965
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Escherichia coli	7792, 3333
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Enterococci	7790, 3332
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Total coliforms	31757, 32064
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Clostridium perfringens	7789, 3331
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Turbidity	7965, 2940

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.

3. 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. Proactively monitor and suitably respond to the risk of algal blooms and other pollution incidents at Longham Lakes (Lake 1 and 2).
   Date: Ongoing for the duration of this Notice.
2. Raw water continuous monitoring for ammonia, dissolved oxygen, conductivity, pH, turbidity and colour at the point of abstraction, with suitable alarm triggers and response procedures in place.
   Date: Ongoing for the duration of this Notice.
3. Maintain contingency plans to protect human health in the event of a risk to human health associated with drinking water quality, which should include proactive liaison with local and regional public health officials.
   Date: Ongoing for the duration of this Notice.
4. Risk informed monitoring for chironomid larvae at a representative point post all slow sand filters (SSFs) at Alderney Water Treatment Works (WTW).
   Date: Ongoing until all SSFs are no longer in supply.
5. Maintain and regularly check the integrity of the isolation valve between the treated water and the abandoned Contact Tank 6.
   Date: Ongoing for the duration of this Notice.
6. Monthly inspections and cleaning of the roof drains on Reservoirs 7 and 8.
   Date: Ongoing for the duration of this Notice.
7. Monthly inspection of hatch integrity and remediation of any identified issues for hatches over partially or fully treated water.
   Date: Ongoing for the duration of this Notice.
8. Ensure the partially treated water presented for ultraviolet (UV) disinfection is within the design envelope and capability of the installed UV units and subject to sufficient preliminary treatment. Ensure the effectiveness of the UV disinfection is verified.
   Date: Ongoing for the duration of this Notice.
9. Weekly sampling for microbiological parameters from each individual SSF at Alderney WTW.
   Date: Ongoing until all SSFs are no longer in supply.
10. Continuous monitoring and recording of UV intensity, UV dose and flow of water through the plant.
    Date: Ongoing for the duration of this Notice.
11. Continuous monitoring for Cryptosporidium from the Supply Point.
    Date: Ongoing for the duration of this Notice.
12. Undertake effective liaison with relevant stakeholders to allow appropriate response to upstream sewage events.
    Date: Ongoing for the duration of the Notice.

(b) To review, revise or make operational the following measures, by the dates specified in each case:

Slow sand filters (SSFs)and associated assets

1. Complete or implement the following as specified:
   1. Complete a critical review of the Alderney WTW slow sand filter maintenance, operation, and management procedures.
      Date: Complete
   2. Complete the revision of the Alderney WTW slow sand filter maintenance, operation, and management procedures, following the findings of the critical review in (b)1.1. This revision must include the items listed in Annex 1 as a minimum standard.
      Date: Complete
   3. Implement the revised slow sand filter maintenance, operation and management procedures completed under (b)1.2. and operate all the Alderney WTW slow sand filters in accordance with these procedures.
      Date: Complete
   4. Complete the training of all relevant personnel to achieve competency in the revised slow sand filter maintenance, operation and management procedures implemented under measure (b)1.3.
      Date: Complete
2. Remove or ensure the external pipework to the underdrains of the SSFs is water- and vermin- proof to prevent contamination from entering the filtered water stream.
   Date: Complete
3. Complete the investigation into the poor performance of SSF 8 and implement any resulting required actions.
   Date: Complete
4. Replace or regenerate the SSF media (granular activated carbon (GAC) and sand), and inspect the SSFs, in accordance with the dates set in Annex 2.
   Date: Ongoing for the duration of the Notice.
5. For the SSF collection chamber:
   1. Complete an internal inspection of the SSF collection chamber.
      Date: Complete
   2. Implement appropriate mitigation to address any risks identified under (b)5.1. above.
      Date: Complete
6. For Reservoirs 1A and 1B:
   1. Complete a remote operated vehicle (ROV) internal inspection.
      Date: Complete
   2. Implement appropriate mitigation to address any risks identified by the ROV completed under measure (b)6.1.
      Date: Complete
   3. Complete an internal inspection of Reservoirs 1A and 1B.
      Date: Complete
   4. Implement appropriate mitigation to address any risks identified under (b)6.3. above.
      Date: Complete
7. For the Wet well chambers:
   1. Complete an internal inspection of the Wet Well Chambers.
      Date: Complete
   2. Implement appropriate mitigation to address any risks identified under (b)7.1. above.
      Date: Complete

East-side contact tank

8. Complete an internal inspection of the east-side of the Contact tank.
   Date: Complete
9. Implement appropriate mitigation to address any risks identified from the internal inspection of the east-side of the contact tank, completed under measure (b)8. above.
   Date: Complete

Reservoir 3

10. Complete an external inspection of Reservoir 3. This must include an inspection of:
    • The integrity of the membrane;
    • Hatches and their openability;
    • Vegetation and tree growth in the exposed flanks; and
    • Potential ingress in the exposed flank.
      Date: Complete

11. Implement appropriate mitigation to address any risks identified under (b)10. above.
    Date: Complete

Reservoir 7

12. Isolate reservoir 7 from supply to enable measures (b)13. and (b)14. to be completed.
    Date: Complete (01 October 2021)
13. Complete an internal inspection (water quality risks and structural integrity risks) of Reservoir 7. The inspection must take into consideration the previously identified issues in the 2012 internal inspection and the ROVs completed in 2019 and 2021.
    Date: Complete
14. Complete any necessary works to mitigate the risks identified under (b)13. to enable the return of Reservoir 7 to supply.
    Date: Complete
15. Fully investigate the integrity of Reservoir 7’s roof (including roof drainage). Install an external roof membrane on Reservoir 7 and implement any other enhancements required to ensure the roof is watertight and ingress is prevented.
    Date: Complete

External Maintenance checks of treated or partially treated water storage tanks

16. Review the suitability of the procedure for ongoing external maintenance checks of treated or partially treated water storage tanks at Alderney WTW. This is to be reviewed against checks that are being completed on-site.
    Date: Complete
17. Following the review completed in (b)16., rectify any identified deficiencies within the procedure and then instigate appropriate ongoing maintenance checks for treated or partially treated water storage tanks at Alderney WTW.
    Date: Complete

Water Fittings

18. Complete a water fittings inspection of Alderney WTW.
    Date: Complete
19. Implement measures to address the findings of the water fittings inspection completed under measure (b)18.
    Date: Complete

Other

20. Inspect a minimum of one of the Longham pressure filter vessels every calendar year and complete any identified required actions (including potential further filter inspections, on the basis of identified risk).
    Date: Ongoing for the duration of this Notice

(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). This must include:
   1. Detailed specification of enhanced monitoring to be undertaken (parameters and frequencies);
   2. Ownership of the audit strategy (roles and responsibilities); and
   3. Specified review of all monitoring data and resulting action.
      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 Alderney WTW, 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. Report summarising the outcome of the SSF maintenance, operation and management procedures review (measure (b)1.1.), accompanied by the revised procedures (measure (b)1.2.), confirmation of the implementation of the revised procedure and appropriate training (required under measure (b)1.3.) and (b)1.4.).
   Date: Complete
3. Evidenced completion of measures (b)2.
   Date: Complete (30 June 2022)
4. Outline any required actions implemented to enhance the performance of SSF 8 (measure (b)3.).
   Date: Complete (30 June 2022)
5. Provide regular updates through South West Water Ltd-Drinking Water Inspectorate liaison meetings on compliance with measures (b)4. and (b)20.
   Date: Ongoing for the duration of the notice
6. Provide an annual confirmation of compliance with measures (b)4. and (b)20.
   Date: Annually by 31 January
7. Summary of the findings of the ROV inspection of Reservoirs 1A and 1B (required under measure (b)6.1.) and confirmation of the completion of any required mitigation (measure (b)6.2.).
   Date: 31 August 2022
8. Summary of the findings of the internal inspections of the SSF collection chamber (measure (b)5.1.), Reservoirs 1A and 1B (measure (b)6.3.), wet well chamber (measure (b)7.1.) and the east side of the contact tank (measure (b)8.) Additionally, provide a summary of any mitigation implemented under measures (b)5.2., (b)6.4., (b)7.2. and (b)9.
   Date: Complete
9. Summary of the findings of the external inspection of Reservoirs 3 required under measure (b)10. and confirmation of the completion of measure (b)11.
   Date: Complete
10. Summary of the findings of the internal inspection of Reservoirs 7 and any mitigation implemented (measure (b)13. and measure (b)14.).
    Date: Completed (30 June 2022)
11. Report outlining the investigation into the integrity of the Reservoir 7 roof; evidence of completion of measures to mitigate the risk; and installation of a new external roof membrane (measure (b)15.).
    Date: Complete (30 June 2022)
12. Report outlining the findings of the review completed under measure (b)16. and the measures taken to address any findings (measure b)17.).
    Date: Complete
13. Report the findings of the water fittings inspection and confirm completion of any required measures to address any risks found (measures (b)18. and (b)19.).
    Date: Complete
14. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete
15. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
16. 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.
17. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: One month after the completion of the new treatment process.

Further Details of this Notice:

4. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
5. 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.
6. 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
04 December 2023
Reference: SWB-2020-00007