Notice of Regulation: Barcombe Mills Treatment Works

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

South East Water Limited –Barcombe Mills Treatment Works

Reference: SEW-2018-00004

Version Number: 5

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): South East Water Limited, with registered number 02679874 (hereinafter called ‘the Company’).

Assets Affected:

  • T030 Barcombe Mills No.1 Works, T031 Barcombe Mills No.2 Works
  • Z047- Barcombe Water Supply Zone

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 1 September 2017, which states that there is or has been a significant risk of supplying water from Barcombe Mills 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:

Description of Risk

Hazard/ Hazardous Event/ Parameter

Hazard I D

Consumer acceptability (discolouration)

Manganese (Total)

324458

Consumer acceptability (discolouration)

Iron (Total)

324456

Risk of failure to meet the requirements of Regulation 26.

Cryptosporidium oocysts (Confirmed)

324486

Risk of failure to meet the requirements of Regulation 26.

Turbidity

324444

Risk of failure to meet the requirements of Regulation 26.

Total coliforms (confirmed)

324479

Risk of failure to meet the requirements of Regulation 26.

Residual Disinfectant-free

324483

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.

Requirements:

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

  1. Optimisation of all existing treatment processes, particularly particulate removal stages to comply with Badenoch and Bouchier recommendations
    Date: Ongoing for the duration of this Notice
  2. Implement a documented strategy for managing raw water quality, including monitoring and managing algae in the river and the raw water storage reservoir, to ensure that treatment processes important for particulate removal are not compromised and forced to operate outside documented operational limits (as specified in 1 above).
    Date: Ongoing for the duration of this Notice
  3. Continuous final water monitoring for Cryptosporidium.
    Date: Ongoing for the duration of this Notice
  4. Continuous online turbidity monitoring upstream of UV treatment and chlorine contact, with appropriate alarms and failsafe shutdown on both treatment streams, as appropriate
    Date: Ongoing for the duration of this Notice
  5. Continuously review all critical control points and mitigation measures for the duration of this notice with a view to updating the notice with additional measures where required
    Date: Ongoing for the duration of this Notice
  6. Ensure that the works operators have an adequate recourse to scientific water quality and management support in the event of a deterioration in works’ performance.

Date: Ongoing for the duration of this Notice

  1. Comply with the requirements of regulation 35(6) and the Water Industry (Suppliers’ Information) Direction 2017, to notify the Inspectorate, Public Health England and local authorities in response to events where there is a potential risk to public health from water supplied from Barcombe Mills Works.

Date: Ongoing for the duration of this Notice

  1. Operate Barcombe No 2 contact tank to ensure the risk of ingress is minimised by keeping positive hydrostatic pressure in relation to the surrounding subsurface water levels.

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:

Risk Assessment and Gap Analysis

  1. Establish the baseline water quality performance for the Barcombe Mills No.1 and No.2 Works based on the design criteria for the works, maximum flows and loading rates for each process and put procedures in place to ensure that the works is operated within the established criteria, with appropriate alarms and shutdown response where required.

Date: Complete

  1. Complete a detailed risk assessment of Barcombe Mills No.1 and No.2 Works and the associated supply system, involving a full review of hazards, points of failure and critical control points and existing controls (adopting a HazRev approach), and identify improvement measures.

Date: Complete

Raw Water Storage

  1. Complete reactive dredging of the raw water reservoir to remove accumulated sludge and implement a routine dredging assessment and dredging as required
    Date: Complete

Supernatant Return (from sludge processing)

  1. Move outfall of supernatant return further away from treatment works intake.

Date: Complete

  1. Install appropriate metering, monitoring, sampling arrangements and laboratory analysis to adequately risk assess the supernatant return to the head of Barcombe Mills works’ raw water reservoir.
    Date: Complete
  2. Install online continuous monitoring for manganese at a suitable point or points, with appropriate alarms, to monitor the effectiveness of manganese removal in No.1 and No.2 treatment streams.
    Date: Complete

Chlorine Contact Tanks

  1. Undertake an internal inspection of contact tank No.2 at works No.2 and complete necessary cleaning.

Date: Complete

  1. Complete a critical review of the operational hazards associated with Barcombe Treatment Works Contact Tanks, with specific consideration given to all structural defects, in particular those identified during the internal inspection carried out on 25 September 2019 and March 2021.
    Date: Complete
  2. Complete a review to identify options to address structural defects identified. Date: Complete
  3. Commence the chosen option of the optioneering review.

Date: Complete

  1. Install suitable piezometric monitoring in association with the Barcombe No.2 contact tank

Date: 31 August 2022

  1. Provide a suitable dewatering programme to facilitate the effective tank repair.

Date: 30 September 2022

  1. Complete contact tank remedial work or suitable alternative solutions and undertake suitable validation monitoring.

Date: 31 March 2023

  1. Complete all remedial works to the contact tank drainage system which are pertinent to the operation of the Barcombe No.2 contact tank

Date: 31 March 2024

  1. Following the inspection, complete monitoring of the effectiveness of the dewatering, the tanks structural condition and potential for movement/further defects to be manifesting. To include internal inspection by an independent chartered engineer.

Date: 31 March 2024

  1. Undertake suitable geophysical surveys to confirm current ground conditions below and near the tank

Date: 30 April 2023

  1. Confirm and make changes as appropriate to establish that the Barcombe Mills export to Arlington Works does not compromise disinfection or disinfection monitoring at Arlington contact tank.

Date: Complete

  1. Ensure sufficient metering, monitors and controls are in place at Barcombe Mills Works to demonstrate disinfection conditions are maintained in the contact tank under all operating conditions. Including flow alterations between Barcombe Mills Works 1 and 2 and also during water transfers from Arlington Works and Cow Wish Works to Barcombe Mills.

Date: Complete

(c) To audit whether the measures have been effective by the following means:

  1. Continuous sampling for Cryptosporidium oocysts at an appropriate sampling point or points representative of treated water supplied from No.1 and No.2 works
    Date: Ongoing for the duration of this Notice
  2. Enhanced operational sampling, for laboratory analysis, for iron, manganese, pH and turbidity in works’ No.1 and No.2 treated waters.
    Date: Ongoing for the duration of this Notice
  3. Continuous demonstration of contact tank inlet turbidity (all inputs), Ct value, pH, retention time, and satisfactory sample analysis.
    Date: Ongoing for the duration of this Notice.

(d) Not to supply water for regulation 4(1) purposes from Barcombe Mills Treatment Works No.1 and Barcombe Mills Treatment Works No.2, 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. To confirm status of steps (b)1 to 7.
    Date: Complete
  3. Provide a summary report from the optioneering review in (b) 9. Confirming the actions and time scale required for Barcombe contact tank 2.
    Date: Complete
  4. Confirm completion of works determined in (b) 13 and confirm validation procedure, including a structural report on the condition of the Barcombe No.2 contact tank considering the asset as a whole including reviewing the known history, age, construction, any defects , ongoing risks and remaining asset life. To be signed off by an independent chartered engineer of a suitable discipline. Provide results of geophysical surveys to confirm current ground conditions below and near the tank
    Date: 31 May 2023
  5. Submit a report in the event that any completed measure of this Notice needs to be altered in any way for any reason
    Date: Ongoing for duration of the notice
  6. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off. To include the following details based on twelve months data:
    • Full structural assessment of the tank undertaken 12 months after the remedial works (b)13 including potential for further structural defects, enhanced bacterial monitoring of the contact tank, results of sampled groundwater to confirm absence of chlorine and results of tank drop tests.
    • An assessment of risks to water quality associated with the processing and importing of sludge from offsite at the Barcombe Mills No.1 and No.2. Works
    • Assessment of disinfection and the impact on disinfection and the ability to meet the requirements of Regulation 26 when the site is importing water from Cow Wish Bottom and Arlington Works.
      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).

Signed

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
08 July 2022
Reference: SEW-2018-00004

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