Notice of Regulation: United Utilities Water Limited – Mitchells Water Treatment Works

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

Reference: UUT-2018-00005

Version Number: 4

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): United Utilities Water Limited, with registered number 02366678 (hereinafter called ‘the Company’).

Assets Affected:

  • Mitchells WTW, T072
  • Mitchells Water Supply Zone, Z102

Details of this Notice:

  1. 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 30 August 2017, which states that there is or has been a significant risk of supplying water from Mitchells WTW (and associated assets as applicable) that 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:

Hazard/ Hazardous Event/ Parameter

Description of Risk

Taste and Odour

Raw water quality outside process design envelope resulting in taste and odour issues.

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.
  1. 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.


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

  1. Continue catchment management measures including working with tenants to reduce nutrient loading and management of source water and abstraction.
    Date: Ongoing for the duration of this Notice
  2. Maintain existing catchment initiatives with external bodies such as: DEFRA, Water Industry Taste and odour management group.
    Date: Ongoing for the duration of this Notice
  3. Maintain enhanced monitoring of raw water sources for chlorophyll A, geosmin and 2-methylisoborneol (2MIB).
    Date: Ongoing for the duration of this Notice
  4. Maintain action trigger levels and appropriate action response as detailed in Mitchells WTW algal (taste and odour) management plan.
    Date: Ongoing for the duration of this Notice
  5. To instigate temporary mobile powdered activated carbon dosing rigs if geosmin and/or 2-MIB is identified above the trigger levels documented in the algal management plan.
    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. A catchment investigation to identify high risk areas and possible sources of nutrient causing taste and odour issues. The Company will work with the Environment Agency to pursue the status as designated a Safeguard Zone for algae.
    Date: 30 September 2022
  2. Confirm process solution following investigations into the viability and validation of UV LED technology.
    Date: Complete
  3. Complete and commission process solution as defined by (b) 2. Solution to include Refurbishment of the first stage filters and replacement of existing media with Granular activated carbon (GAC).
    Date: 31 May 2023

(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 Mitchells 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. Provide a report on catchment investigation regarding safeguard zone to EA.
    Date: 31 October 2022
  3. Confirmation of the process solution report as defined in step (b)2.
    Date: Complete
  4. Completion of the process solution in step (b) 3.
    Date: 30 June 2023
  5. Review the risk assessment for T072 Mitchells WTW as required by regulation 27(4) and subsequently submit a revised regulation 28 report accompanied by a signed board level declaration.
    Date: 31 July 2023
  6. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete
  7. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  8. 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
  9. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 June 2024

Further Details of this Notice:

  1. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
  2. 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.
  3. 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
17 April 2023
Reference: UUT-2018-00003

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