Notice of Regulation: Cheddar Water Treatment Works

NOTICE UNDER REGULATION 28(4) OF THE WATER SUPPLY (WATER QUALITY) REGULATIONS 2016 (AS AMENDED)

Bristol Water Plc: AMP7 Cheddar Water Treatment Works

Reference: BRL-2021-00001

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Bristol Water Plc, with registered number 02662226(hereinafter called ‘the Company’).

Assets affected:
Cheddar Springs Catchment (C05), Cheddar Falls (A23), Cheddar ReservoirOutflow (A07), Cheddar Water Treatment Works (T07), and the Cheddar Supply System (Y05)

  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received multiple regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 23 January 2017, 16 October 2019, and 25 March 2020, which state that there is or has been a significant risk of supplying water from Cheddar 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:

Hazard/ Hazardous

Event/ Parameter

Hazard ID

Description of Risks

No Supply (25/03/2020)

T07Hazard0090

No/low flow through slow sand filter due to blinding from algae.

Total Algae (23/01/2017)

A07Hazard0016

Raw water deterioration increasing the risk of taste and odour metabolite production and blinding of slow sand filters.

Taste and Odour (16/10/2019)

T07Hazard0062

Blinding of slow sand filters from phytoplankton such as Dinobryon blooms increasing risk of taste and odour metabolite production due to anaerobic conditions in slow sand filters.

Ammonium (16/10/2019)

T07Hazard0064

Ammonium risk with potential anaerobic conditions above slow sand filters.

Iron

Arsenic

Lead

Manganese

Aluminium

(all 16/10/2019)

T07Hazard0068

T07Hazard0066

T07Hazard0069

T07Hazard0070

T07Hazard0065

Development of anaerobic conditions due to blinding of slow sand filters from phytoplankton blooms increasing risk of soluble metal release from filter media poses risk to final water quality.


  1. The Company are required to satisfy the following:

Requirements

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

  1. Continue to operate the Cheddar Water Treatment Works (WTW) treatment process to ensure compliance with regulation 26 and regulation 4 of the Water Supply (Water Quality) Regulations 2016 (as amended).
    Date: Ongoing for the duration of this Notice
  2. Routine maintenance checks of the slow sand filters carried out by the treatment works operators.
    Date: Ongoing for the duration of this Notice
  3. Maintain a controlled flow across the slow sand filters. In the event of low flow through the slow sand filters, mitigate the risk of no supply using the Southern Resilience Scheme.
    Date: Ongoing for the duration of this Notice
  4. Monitor the outlet of Cheddar Reservoir regularly for Chlorophyll-α, geosmin and 2-methylisoborneol during the high-risk period (March – October) for phytoplankton blooms associated with taste and odour metabolite production.
    Date: Ongoing for the duration of this notice
  5. Monitor the final treated water at Cheddar WTW for geosmin and 2-methylisoborneol during periods that correlate with high-risk periods.
    Date: Ongoing for the duration of this Notice
  6. Continue investigations into the raw water deterioration and sources of total phosphorus, orthophosphate, nitrate, ammonium, and manganese in the catchment and Cheddar Springs.
    Date: Ongoing for the duration of this Notice
  7. Maintain daily sampling of the combined outlet of the slow sand filters at Cheddar WTW for total coliforms, E. coli, iron, manganese, turbidity, and colour.
    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. Evaluate ultrasound as a control measure for algal blooms in the water held above a slow sand filter at Cheddar works.
    Date: 30 October 2023
  2. Evaluate the effect of ultrasound on numbers of Dinobryon, cyanobacteria, and total phytoplankton in the water held above a slow sand filter compared to other slow sand filters as controls.
    Date: 30 October 2023
  3. Evaluate covering of a slow sand filter as a control measure for algal blooms in the water held above a slow sand filter at Cheddar works.
    Date: 30 October 2023
  4. Evaluate the effect of covering a slow sand filter on numbers of Dinobryon, cyanobacteria, and total phytoplankton in the water held above a slow sand filter compared to other slow sand filters as controls.
    Date: 30 October 2023
  5. Assess the differences in the media (for example silt content) and flow rates of a covered and uncovered slow sand filter.
    Date: 30 October 2023
  6. Evaluate the findings of the investigations from (b)1 – 5 to date and confirm if any additional measures in excess of the Southern Resilience Scheme (SRS) or treatment mitigations in place are required.
    Date: 30 November 2023
  7. Produce a project plan, including timescales for implementation of any additional mitigations required from conclusion of investigation in (b)6.
    Date: 31 December 2023
  8. Implementation of any additional measures required from conclusion of investigations in (b)6.
    Date: 31 March 2025

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

  1. Define an audit strategy to monitor the effectiveness of the above measures specified in section (a) and (b).
    Date: 30 June 2021
  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 Cheddar WTW, 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:

  1. Provide a progress report annually by 31 January and against the following milestones:
    Date: Annually by 31 January
    • Confirm completion of investigations described in sections (b)1 – 5, conclusions of the evaluation from (b)6, and confirm any identified long-term measures required at Cheddar WTW, and plan for implementation as described in (b)7 (if applicable).
      Date: 31 January 2024
    • Confirm delivery of any long-term measures identified as described in (b)8.
      Date: 30 April 2025
  2. Submit the strategy for auditing the effectiveness of the measures, as specified in (c)1.
    Date: 31 July 2021
  3. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Ongoing for the duration of this Notice
  4. 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 the duration of this Notice
  5. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 31 January 2026

  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
Laura Moss
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
20 April 2021
Reference: BRL-2021-00001
Version 1

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