Severn Trent Water Limited – Boughton Works UV
Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended)
Reference: SVT-2025-00017
Version Number: 1
Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Severn Trent Water Limited, with registered number 02366686 (hereinafter called ‘the company’).
Assets Affected:
- Boughton WTW T100
- Chester, Wrexham Y003
Details of this Notice:
- 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 17 September 2025, which states that there is or has been a significant risk of supplying water from Boughton works (and associated assets as applicable) that could constitute a potential danger to human health or could be unwholesome.
- 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 |
|---|---|---|
Failure of treatment process to prevent Cryptosporidium entering supply. | Cryptosporidium – C111 | T100-11137-T-C111-C111-24U |
Failure of treatment process to prevent Enterococci entering supply. | Enterococci – C003 | T100-11137-T-H035-C003-2Q2 |
Inadequate management of Turbidity upstream of the disinfection process. | Turbidity – A002 | T100-11137-T-A002A-A002-004 |
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.
- 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:
- Operate Boughton works in accordance with company policy, standards, and procedures, aligning with recognised standards of good practice.
Date: Ongoing for the duration of this Notice - Continuous monitoring of turbidity at critical points of the treatment process including immediately prior to disinfection, linked to appropriate alarms and action triggers.
Date: Ongoing for the duration of this Notice - Continue to monitor raw water for Cryptosporidium at an enhanced frequency of twice weekly.
Date: Ongoing for the duration of this Notice - Continue continuous monitoring for Cryptosporidium in the final water, including daily cartridge changes.
Date: Ongoing for the duration of this Notice - Enhanced monitoring of final water for Enterococci.
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:
- Carry out a HAZREV for Boughton water treatment works and determine any further steps needed to reduce risk to the treatment process and Regulation 26.
Date: 30 June 2026 - Complete a review of the treatment process to identify appropriate systems for running to waste or containment of water supplies that are improperly treated.
Date: 30 June 2026 - Complete the installation of a generator and associated controls for the clarified reservoir pumps.
Date: 31 August 2026 - Complete the implementation of clarified reservoir pump automation to protect saturator feed.
Date: 31 December 2026 - Complete the outline design of the proposed UV solution.
Date: 30 April 2027 - Complete the detailed design of the proposed UV solution and confirm the expected start date for construction.
Date: 31 January 2028 - Complete the construction and commissioning of the UV solution.
Date: 31 December 2028
(c) To audit whether the measures have been effective by the following means:
- Define an audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
Date: 31 July 2026 - 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 Boughton works, or not to so supply unless the specified conditions below are satisfied:
- 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:
- Provide a progress report annually.
Date: by 31 January each year. - Provide a report detailing the outcome of the HAZREV and any further steps being carried out to reduce process risk at Boughton works.
Date: 31 July 2026 - Provide a report confirming the outcome of the treatment process review to identify appropriate systems for running to waste or containment of water supplies that are improperly treated.
Date: 31 July 2026 - Provide a report confirming the installation of the generator and associated controls for the clarified reservoir pumps.
Date: 30 September 2026 - Provide a report confirming automation of the clarified reservoir pumps to protect saturator feed.
Date: 31 January 2027 - Provide a report confirming outline design of the UV solution.
Date: 31 May 2027 - Provide a report confirming detailed design of the UV solution and expected start date for construction.
Date: 29 February 2028 - Provide a report confirming the completion of the construction and commissioning of the UV solution.
Date: 31 January 2029 - Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: 31 August 2026 - Submit any revisions of the audit strategy produced under measure (c)2.
Date: Within 1 month of a revision - 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 - 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:
- Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
- 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.
- 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
27 May 2026
Reference: SVT-2025-00017