Undertakings: Thames Water – Bulk Imports

WATER INDUSTRY ACT 1991(AS AMENDED): SECTION 19(1)(b)

THE SECRETARY OF STATE FOR ENVIRONMENT, FOOD, AND RURAL AFFAIRS:

  1. is satisfied that Thames Water “the Company” in supplying water from imported water from Grafham, Morcott and Wing treatment works which may be at risk of exceeding the standards for metaldehyde and total pesticides. This means that the Company is likely to contravene its duty in respect of supplying water which meets the Regulations under Section 68(1)(a) of the Water Industry Act 1991 (as amended) and meets the requirement set in regulation 4(2)(c) of the Water Supply (Water Quality) Regulations 2016 (as amended).
  2. notes that Thames Water has on 30 April 2020 given a new undertaking (DWI Ref No: TMS-2020-00006) under the provisions of paragraph 2(b) of the previous undertaking given on 25 July 2014 (DWI Ref no: TMS3390) to replace the undertaking and to take the following steps by the dates shown:

Steps to be taken

(a)

Ensure that metaldehyde and total pesticides have been assessed as hazards as part of the Regulation 27 Risk Assessment for the supply system(s) supplied by Anglian Water’s Grafham, Morcott and Wing WTWs according to a Drinking Water Safety Plan approach.
Date: Completed

(b) Short term measures

  1. Implement an enhanced monitoring strategy to supplement current regulatory monitoring.
    Date: With immediate effect and for the duration of the Undertaking
  2. The Company will take all reasonable steps to ensure that the prescribed concentration(s) are not exceeded and any steps necessary must be taken to protect public health. If the concentration in any water sample exceeds the maximum concentration the Company has agreed with Public Health England in the water supply zones listed in the Annex to this Schedule of Works, take all reasonable measures in consultation with local health professionals to minimise the impact on customers.
    Date: With immediate effect and for the duration of the Undertaking
  3. Report regulatory exceedences of the standards for the metaldehyde and total pesticides parameters to DWI as part of the current monthly exception reporting process.
    Date: With immediate effect and for the duration of the Undertaking
  4. The Company will implement any reasonably necessary short-term operational measures within the company’s power to implement.
    Date: With immediate effect and for the duration of the Undertaking

(c) Medium term measures

  1. Continue to monitor water quality in the zones supplied from the above-named bulk imports, and liaise regularly with Anglian Water on progress with the measures being taken to secure compliance with the metaldehyde standard at the above-named WTWs.
    Date: Ongoing until the revocation of this undertaking.
  2. Provide support as required to national, regional and local catchment management initiatives aiming to influence metaldehyde usage in high risk catchment areas and reduce the amounts reaching water sources.
    Date: Ongoing until the revocation of this undertaking.

(d) Long term measures:

Continually appraise the risk of metaldehyde and the total pesticides parameters as hazards as part of the Regulation 27 Risk Assessment for the supply system(s) associated with Anglian Water’s Grafham, Morcott and Wing WTWs according to a Drinking Water Safety Plan approach, and ensure that Regulation 28 documents are regularly reviewed and updates provided.
Date: Ongoing

(e) Reporting: Provide DWI with reports on progress made.

Date: At yearly intervals for the duration of the undertaking. Reporting periods are January to December. Reports to be submitted by 31st January each year that the Undertaking is in place (except for Jan 2025).

Reports to include at least the following details:

  1. Metaldehyde monitoring data for the zones listed in the Annex to this schedule;
  2. A summary of activities carried out under step (d) above, and the outcomes;
  3. Details of contacts made with the supplying water company concerning the actions that company is undertaking to address the risk of metaldehyde in the water supplied;
  4. Any other relevant information.

(f)

Provide a final report to DWI on the outcome of the activities undertaken by Anglian Water at Grafham, Morcott and Wing WTWs, the solutions implemented and the conclusions drawn from other work carried out. Include as evidence of closure for this scheme appropriate documentation to confirm that the actions set out in this Schedule of Works have been completed and the extent to which the required outcomes have been achieved.
Date: 30th April 2025 (one month after receipt of Anglian Water final report) unless Anglian Water closes its Undertaking sooner.


  1. is satisfied that Thames Water has given and is complying with an undertaking to take all such steps as appear to the Secretary of State for the time being to be appropriate to secure or facilitate compliance with the requirement of regulation 4(2)(c) of the Water Supply (Water Quality) Regulations 2016 (as amended).

Authorised by the Secretary of State to sign in that behalf:
Milo Purcell
Deputy Chief Inspector
Drinking Water Inspectorate
DWI Ref No: TMS-2020-00006
Date 2 May 2020

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