Severn Trent Water Limited – Trimpley Treatment Works Cryptosporidium
Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended)
Reference: SVT-2024-00004
Version Number: 2
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:
- T0093 – Trimpley WTW
- Supply systems: YSEV02, YSEV06, YSEV08, YSEV09, YSEV13, YSEV18, YSEV20
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 27 June 2023, which states that there is or has been a significant risk of supplying water from Trimpley water treatment 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 |
T0093-349-T-C111-C111-24U |
- The Company is 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 Trimpley water treatment works in accordance with company policy, standards, and procedures, aligning with recognised standards of good practice.
Date: Ongoing for the duration of this Notice - Continue to monitor the raw water, including Cryptosporidium, at the current frequencies (a minimum of twice weekly for Cryptosporidium) and in accordance with the Company’s procedures, in order to understand and assess the raw water quality risk posed. Carry out speciation of raw water samples, where Cryptosporidium are recovered in sufficient numbers (greater than or equal to 5 oocysts per sample).
Date: Ongoing for the duration of this Notice - Continue to monitor the final water, including continuous monitoring for Cryptosporidium, with daily cartridge changes and in accordance with the Company’s procedures.
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:
- Conduct a hazard review into the catchment risks at Trimpley works. Give due consideration to the sources of Cryptosporidium in the catchment and the possible causes of increased risk.
Date: Complete - Review the investigatory sampling procedures to ensure Cryptosporidium samples are collected at a suitable frequency and in a timely manner to inform the extent of the failure and to assist in determining the requirement of possible precautionary advice.
Date: Complete - Review whether additional data inputs to the CFD model or further assessment of Trimpley reservoir are required.
Date: Complete - Review the sampling data and amend where necessary the suitable frequencies and triggers for the work’s raw water turbidity and Cryptosporidium detections.
Date: Complete - Complete a review of the performance of each of the treatment stages at Trimpley works to evaluate whether the current processes in place are effective for the removal of Cryptosporidium under all circumstances. Date: Complete
- Complete a review of the procedures, training and competency relating to the operation of Trimpley treatment works to ensure that the works performance remains optimised at all times.
Date: Complete - Design additional treatment options, or modifications to existing treatment, for Trimpley treatment works, based upon the findings of steps (b)1 to (b)6.
Date: Complete - Complete the design of an ultra-violet (UV) treatment solution.
Date: 31 March 2027 - Confirm the start date for construction of the UV treatment solution.
Date: 30 September 2028 - Complete the construction and commissioning of the UV treatment solution.
Date: 31 March 2030
(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: Complete - 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 Trimpley water treatment 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. - Submit a report on the conclusions of the hazard review into the catchment risks at Trimpley works.
Date: Complete - Provide a report detailing the review of investigatory sampling procedures in response to Cryptosporidium detections in final water.
Date: Complete - Provide a report on whether additional data inputs to the CFD model or further assessment of Trimpley reservoir are required.
Date: Complete - Provide a report detailing the review of potential additional data inputs or assessment of Trimpley reservoir.
Date: Complete - Provide a report detailing the review of sampling data, raw water turbidity triggers and Cryptosporidium detections.
Date: Complete - Provide a report detailing the review of the performance of each of the treatment stages at Trimpley works showing an evaluation of whether the current processes in place are effective for the removal of Cryptosporidium under all circumstances and what changes will be or have been introduced.
Date: Complete - Provide a report detailing the review of procedures, training and competency at Trimpley works.
Date: 31 Complete - Provide a report detailing the assessment of whether additional treatment options or modifications to existing treatment are required for Trimpley works.
Date: Complete - Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: Complete - Provide a report confirming the completion of the design of the UV solution.
Date: 30 April 2027 - Provide a report confirming the start date for construction of chosen UV solution.
Date: 31 October 2028 - Provide a report confirming completion of construction and commissioning of UV solution.
Date: 30 April 2030 - 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: 30 April 2031
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).
Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
11 April 2025
Reference: SVT-2024-00004 v2