South West Water Limited – Enhanced Cleaning and Inspection of Drinking Water Storage and Chlorine Contact Tanks

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

Reference: SWB-2020-00009

Version Number: 10

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:

• The treated water storage (and chlorine contact) tanks in the South West Water Ltd. supply region.

Details of this Notice:

1. The Drinking Water Inspectorate (‘the Inspectorate’) has received asset of regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 21 October 2020, which states that there is or has been a significant risk of supplying water from treated water storage (and chlorine contact) tanks in the South West Water Ltd. supply region (and associated assets as applicable) that could constitute a potential danger to human health.
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
To address the potential risks of ingress and microbial re-growth.	Total Coliforms
To address the potential risks of ingress and microbial re-growth.	E. coli
To address the potential risks of ingress and microbial re-growth.	Enterococci
To address the potential risks of ingress and microbial re-growth.	Colony Counts at 22°C
To address the potential risks of ingress and microbial re-growth.	Residual Disinfectant – Total Chlorine
To address the potential risks of ingress and microbial re-growth.	Residual Disinfectant – Free Chlorine

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. Operate all chlorine contact and treated water storage tanks in accordance with current company policy, standards and procedures aligning recognised standards of good practice. To include:

• Maintain a proactive inspection and cleaning programme including a robust integrity testing procedure (roof inundation and independent observation).
• Maintain proactive external inspections, grounds maintenance, site security and asset maintenance including periodic inspection of hatches, seals, redundant assets, sample taps, overflows, washouts, and air valves.
• Maintenance of suitable records of remedial work completed on all assets.
• Escalation of all issues that present a risk to water quality.
• Keep under review residual chlorine concentrations to ensure appropriate set points and trigger values are in place to prevent a deterioration of drinking water quality.
  Date: Ongoing for the duration of this Notice

2. For all treated water storage (and chlorine contact) tanks, where ingress is identified:

• Implement immediate mitigation measures to ensure public health is protected.
• Complete any remedial work required at the earliest opportunity.
  Date: Ongoing for the duration of this Notice

3. Carry out enhanced monitoring for any tank where a risk to water quality has been identified including, as a minimum, those sites listed in Annex 1.
   Date: Ongoing for the duration of this Notice
4. Include as part of the Company’s Drinking Water Safety Plan (DWSP), a risk assessment of the turnover of stored drinking water.
   Date: Ongoing for the duration of this Notice
5. Maintain appropriate contingency plans to ensure drinking water quality and sufficiency can be maintained in the event of a risk associated with drinking water quality, in line with industry good practice.
   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. Confirm which treated water storage tanks have not been physically drained and inspected within 10 years and record in Annex 1 and the Company’s DWSP.
   Date: Complete
2. Review Annex 1 on at least an annual basis to ensure that any tanks outside of the 10-year cleaning and inspection frequency are included and update the risk assessments for any site included within this list.
   Date: Biannually by 31 March and 30 September each year
3. Using a risk-based approach:
   a) Conduct a review of how all treated water storage tanks/cells are removed from supply.
   Date: Complete
   b) Develop a plan and schedule of works (with timescales) to complete the physical internal inspections and any remedial works identified for all tanks, excluding those identified as requiring significant enabling works and requiring deferral until AMP 8 as listed in Annex 2 below.
   Date: Complete
   c) Implement this plan to completion for all tanks that can be readily removed from supply in AMP 7 (i.e. excluding those identified in Annex 2).
   Date: Complete
4. For all treated water storage tanks which cannot be removed from supply in AMP7 due to the nature of the enabling works required:
   a) Update the regulation 28 risk assessments to reflect this risk.
   Date: Complete
   b) Confirm this list of tanks in Annex 2 including date of last physical internal inspection and the interventions required to enable these tanks to be removed from supply.
   Date: Complete
   c) For PR24 planning purposes, develop a plan and schedule of works that require AMP8 delivery for enabling works, including mitigation measures required should the tank need to be removed from supply in the interim.
   Date: Complete
5. Review all treated water (and chlorine contact) tank schematics and ensure drawings are up to date and include locations of regulatory sample taps, any online water quality monitors, tapping points, the outflow discharge points and all relevant valves (including air valves).
   Date: Complete
6. Develop a risk-based approach to determine the physical inspection (internal and external) frequency of all treated water storage and chlorine contact tanks. To include the findings from the DWSP risk assessment in (b)7.
   Date: By the dates listed in Annex 1.
7. DWSP risk assessment for tanks should follow industry good practice and include as a minimum:

• Time since last inspection.
• Date of construction/age.
• Materials of construction / tank design.
• Water quality history (to include as a minimum E. coli, coliforms, and colony counts).
• Turnover and tank hydraulics.
• Points of potential ingress (hatches, seals, redundant assets, overflows, washouts, and air valves).
• Sample tap condition, tapping points, sample lines and material.
• Any other risks related to individual tanks.

8. Review and revise current drinking water storage policy to account for the requirements of (b)6 and (b)7 above.
   Date: Complete
9. For all treated water storage (and chlorine contact) tanks, develop a plan and schedule of works (with timescales) to complete physical internal inspections and any remedial works required, in line with the new revised risk assessment frequency defined in (b)6 and (b)7 and commence implementation of this plan.
   Date: Complete

(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 treated water storage tanks, 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 the list of treated water storage tanks that have not been drained or inspected within 10 years in Annex 1 and record in the Company’s DWSP.
   Date: Complete
3. Confirm completion of the review of how all treated water tanks/cells are removed from supply.
   Date: Complete
4. Provide a populated Annex 2 with a list of tanks, including date of last physical internal inspection and the interventions required to enable these tanks to be removed from supply and provide updated regulation 28 risk assessments as specified in (b)4 a. and (b)4 b.
   Date: Complete
5. Provide the risk-based plan and schedule of works (with timescales) to complete the physical internal inspections and any remedial work required for all tanks, excluding those identified as requiring significant enabling works and requiring deferral until AMP 8 as listed in Annex 2.
   Date: Complete
6. Confirm completion of the risk-based schedule of works for completing physical internal inspections, as specified in (b)3 c.
   Date: Complete
7. Provide the plan and schedule of works that require AMP8 delivery for enabling works, including mitigation measures required should the tank need to be removed from supply in the interim, as specified in (b)4 c.
   Date: Complete
8. Following review of tank site schematics, as specified in (b)5, confirm all site schematics are up to date.
   Date: Complete
9. Provide the risk-based approach developed to determine inspection (internal and external) frequency of all tanks, as specified in (b)6.
   Date: Complete
10. Provide the revised drinking water storage policy.
    Date: Complete
11. Provide the plan and schedule of works for physical internal inspections in line with the revised risk assessment frequency for all tanks and demonstrate that the implementation of the plan has commenced.
    Date: Complete
12. Submit any updates to Annex 1, as specified in (b)2 for any Annex 1 tanks where a physical internal inspection, cleaning, and any required remedial work has been completed under (b)3 in advance of 31 December 2023. Submit evidence demonstrating completion with an accompanying regulation 28(1) report for the tank and an updated Annex 1 list for this Notice.
    Date: Complete
13. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete
14. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
15. 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.
16. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 31 January 2026

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
20 December 2024
Reference: SWB-2020-00009 v10