Wessex Water Services Limited – Sturminster Marshall/Shapwick Water Treatment Works Nitrate

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

Reference: WSX-2018-00002

Version Number: 2

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Wessex Water Services Limited, with registered number 02366648 (hereinafter called ‘the Company’).

Assets Affected:

Asset Name

Reference

Sturminster Marshall/Shapwick Water Treatment Works

T33126200

Zone 92 Shapwick Supply System

Y44000092

Zone 95 Lytchett Matravers Supply System

Y44000095

Zone 98 Corfe Mullen Supply System

Y44000098

Table 1: List of assets affected and associated reference numbers

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 28 December 2017, which states that there is or has been a significant risk of supplying water from Sturminster Marshall/Shapwick Water Treatment Works (and associated assets as applicable) that could constitute a potential danger to human health or 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 nitrate.
  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. Continuation of catchment management activities.
    Date: Ongoing for the duration of this Notice
  2. Regular operation:
    • Monitor/alarm systems; and
    • Maintain site operating procedures and training documentation.
      Date: Ongoing for the duration of this Notice
  1. Routine Maintenance:
    • Raw and treated nitrate monitors calibrated at a minimum monthly frequency;
    • Monitors also re-calibrated following a water quality event or evidence of drift; and
    • Raw and treated nitrate monitors serviced at a minimum six-month frequency.
      Date: Ongoing for the duration of this Notice
  1. Water quality monitor data reviewed and appropriate process changes made.
    Date: Ongoing for the duration of this Notice
  2. Auto shutdown:
    • Pre-contact tank nitrate – High alarm trigger 47.8 mg NO3/L (10.8 mg N/L); and
    • Review and adjust shutdown trigger level if appropriate.
      Date: Ongoing for the duration of this Notice
  1. Ability to flush to waste following site shutdown, enabling unacceptable water to be disposed of.
    Date: Ongoing for the duration of this Notice
  2. Routine operational and regulatory water quality sampling of the raw and treated water to validate that the site is operating according to procedures. Any result detected outside of acceptable limits is recorded and published on a daily exception report and investigated.
    Date: Ongoing for the duration of this Notice
  3. Increase water quality sampling frequency in response to results detected outside of acceptable limits
    Date: Ongoing for the duration of this Notice
  4. Operational borehole selection to enable isolation of individual boreholes.
    Date: Ongoing for the duration of this Notice
  5. Maintain a site-specific nitrate plan.
    Date: Ongoing for the duration of this Notice
  6. Advise health authorities of any exceedances of the prescribed concentration value for nitrate.
    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. Complete detailed design and obtain permission (if required) for blending facilities for water from Sturminster Marshall/Shapwick Water Treatment Works to include:
    • Washout improvements at Shapwick to enable each borehole to be washed out independently;
    • Enable the Shapwick/Sturminster flows to be blended in a controlled manner with multiple sources;
    • A pump to Sturminster Marshall contact tank for controlled blending of multiple treated water sources prior to Sturminster Marshall Grid Service Reservoir; and
    • Increased nitrate monitoring and control facilities, linked to appropriate alarms and response triggers, to verify mitigation of the nitrate risk.
      Date: Complete
  1. Construct, commission and make operational (and maintain thereafter) the chosen blending facilities (developed under measure (b)1) for water from Sturminster Marshall/ Shapwick Water Treatment Works to ensure compliance with the nitrate standard.
    Date: 31 March 2024

(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)., to include as a minimum:
    • Monitor raw and treated nitrate levels through compliance and operational sampling at an enhanced frequency (minimum twice weekly) for a minimum period of 12 months following completion of construction as specified in (b)1. and (b)2. above to monitor ongoing effectiveness;
    • Validation of models used to calculate nitrate blend ratios;
    • Review raw and treated nitrate monitor and sampling data to demonstrate effectiveness of the constructed blending facilities; and
    • Review annual catchment management reports.
      Date: Complete
  1. 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 Sturminster Marshall/ Shapwick Water Treatment Works, 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. Submit improvement programme scope following completion of detailed design.
    Date: Complete
  3. Submit a report following the construction and commissioning of the blending facilities as required under measure (b)2.
    Date: 30 April 2024
  4. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete
  5. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  6. 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
  7. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 April 2025

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).

Signed

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
20 October 2022
Reference: WSX-2018-00002 V2

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