Dwr Cymru Cyfyngedig – Chlorate Risk Management
Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2018
Reference: DWR-2023-0010
Version Number: 1
Water undertaker as appointed under section 6 of The Water Industry Act 1991 (as amended): Dwr Cymru Cyfyngedig, with registered number 02366777 (hereinafter called ‘the Company’).
Assets Affected:
- All assets which store and/or dose sodium hypochlorite (automatic or manual), and other sodium hypochlorite storage depots that are not assets in the Company’s supply region.
Details of this notice:
- The Drinking Water Inspectorate (‘the Inspectorate’) has received a regulation 28(1) report of the Water Supply (Water Quality) Regulations 2018 (‘the Regulations’) from the Company dated between 20 October 2022 and 31 May 2023, which states that there is or has been a significant risk of supplying water from company assets which use sodium hypochlorite as a treatment chemical or store sodium hypochlorite (and associated assets as applicable) that could constitute a potential danger to human health or could be unwholesome.
- Consequently, this notice is served on the Company by the Inspectorate on behalf of the Welsh Ministers, under regulation 28(4) for the assets listed above, for risks associated with:
|
Hazard/ Hazardous Event/ Parameter |
Hazard I D | |
|---|---|---|
|
Potential for elevated levels of Chlorate due to dosing of sodium hypochlorite. |
Chlorate (D101) |
Applicable across the company wherever sodium hypochlorite is dosed, for example: Penycefn WTW 10957493 Penyball SRV 10956828 Capel Curig WTW 11317169 |
|
Potential for elevated levels of Chlorate due to sodium hypochlorite storage conditions. |
Chlorate (D101) |
Applicable across the company wherever sodium hypochlorite is stored, for example: Penycefn WTW 10957494 Penyball SRV 10956829 Capel Curig WTW 11208602 |
- 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:
- A routine chlorate monitoring programme for every asset where there is the potential for chlorate to be formed, such as where sodium hypochlorite or chlorine dioxide is dosed.
Date: Ongoing for the duration of this notice - Recording of sodium hypochlorite storage tank level data.
Date: Ongoing for the duration of this notice - Maintain compliance with the procedures relating to ambient and chemical temperature monitoring (PO322 and PN321), escalating where temperature exceeds trigger values set out in these documents.
Date: Ongoing for the duration of this notice - Maintain contingency plans (including liaison with relevant stakeholders, as appropriate) to protect human health.
Date: Ongoing for the duration of this notice - Take all reasonable operational steps (and continue to enhance the effectiveness) to ensure that water that is not compliant with the requirements of regulations 4 and 26 is prevented from entering supply.
Date: Ongoing for the duration of this notice - Maintain site chlorine monitors and associated dosing control equipment in line with company procedures.
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:
- Carry out a review of company risk assessments relating to chlorate to identify any non-compliance with and ensure compliance with regulation 31(2)(b) and the British Standard BS: EN 901. List of sites to be provided to the Inspectorate and annually according to The Water Industry (Suppliers Information) Direction 2023, Annex A and as part of the company’s regulation 28 obligations. Considerations should include but are not limited to:
- Compliance of dosing arrangements with the British Standard.
- Location of tank.
- Whether the sodium hypochlorite (‘chemical product’) is purchased chemical (bulk delivery or carboy), derived from onsite electrolytic generation of chlorine, chlorine dioxide dosing or otherwise.
- Ambient temperature monitoring / Chemical product temperature monitoring (ambient temperature of the sodium hypochlorite storage rooms should be monitored and controlled as part of compliance with the British Standard).
- Maximum chemical product age / maximum turnover time / residence time / volume of tank. This analysis should capture the theoretical worst case scenario that is to say a storage tank at high high level with a minimum chlorine dose at the minimum dosed water flow rate.
- Strength of chemical product.
- Further addition of chemical product for example for oxidation or other treatment process.
- Chlorine demand variations.
- Average flow of site and seasonal flow variations.
- Seasonal variations of network demand and temperature of chemical product (if not temperature control).
- Cumulative effect of any secondary (booster) chemical product dosing.
- Emergency / back up dosing arrangements of chemical product at treatment works and service reservoirs.
- Assets such as treated water tanks and service reservoirs, where manual dosing of chemical product may take place.
- Use of chemical product for mains chlorination for new mains and in emergency circumstances.
- Bulk supplies.
- Available monitoring data.
Date: 31 March 2024
- Review and update chlorate monitoring frequencies for each site where sodium hypochlorite is dosed (including sites where sodium hypochlorite is derived from onsite electrolytic generation of chlorine), using a dynamic, risk-based approach based on information from step b(1) with appropriate reactive triggers based on operational or monitoring data. Monitoring for chlorate should be at a minimum frequency of fortnightly for sites using purchased chemical (bulk delivery or carboy) until any mitigating actions identified in b(11)(a) are completed and including 12 month demonstration of benefit period afterwards. Monitoring should additionally take account of risk, with increased frequency and prioritised analytical turn-around time when risk increases, such as during warmer months and where sites that have continuously monitored chemical product temperature and product strength indicate a significant increase in the formation potential for chlorate in accordance with documented ‘early warning’ triggers.
Date: 31 March 2024 - Ensure all company policies, procedures and training pertaining to sodium hypochlorite delivery, storage, dosing and response to sample results are reviewed and updated where necessary following the chlorate risk assessment described in step b(1).
Date: 31 March 2024 - Review on-site titration frequency for each site where chemical product is stored and/or dosed to verify sodium hypochlorite strength, using a dynamic, risk-based approach based on information from step b(1) with appropriate reactive triggers based on operational or monitoring data. To include all storage tanks at a minimum frequency of three to six months. To assure conformance with the British Standard on receipt of the sodium hypochlorite from the supplier the chemical should fully meet the test requirements of the relevant EN standard by provision of a certificate of attestation for the batch of chemical supplied or by internally checking through their own laboratories. The review should evidence appropriate assessment frequencies and acceptance / escalation criteria in company procedures and records.
Date: 31 March 2024 - Carry out on-site titration for each site according to the frequency determined in step b(4).
Date: 31 March 2024
- Review the retention time of sodium hypochlorite chemical storage, using the outputs from step b(1). Ensure sodium hypochlorite deliveries and storage are managed to prevent chemical retention time exceeding company policy, with a maximum of 28 days for storage, taking into account average dose and flow.
Date: 31 March 2024 - Develop and implement a risk-based programme for draining and cleaning sodium hypochlorite storage tanks, using the outputs from step b(1).
Date: 30 September 2024 - Creation of a chlorine demand calculation for all water treatment works sites where sodium hypochlorite is dosed, with SCADA and telemetry alarms where appropriate. Investigate all breaches according to an appropriate response procedure. This investigation should include an assessment of sodium hypochlorite strength. Date: 30 September 2024
- Review and update any procedures and operational risk assessments where there may be an increased risk of chlorate. For example, altering the chlorine setpoint, when an asset has been removed from supply for a significant amount of time, when service reservoirs are manually dosed with sodium hypochlorite and where emergency mains chlorination is carried out.
Date: 30 September 2024 - Review minimum asset standard for sodium hypochlorite for future installations to ensure compliance with regulation 31(2)(b) to include as a minimum:
- Location of tank.
- Suitable tank materials.
- Storage of bulk and day tanks and of carboys in a suitable location.
- Temperature monitoring for the chemical and storage room.
- Volume of tank / optimisation of residence time and turnover of chemical.
- Ability to drain and rinse the tank completely, prior to delivery of fresh sodium hypochlorite.
Date: 31 March 2024
- Carry out a review of all assets where sodium hypochlorite is dosed or stored and identify any non-compliance with the British Standard BS: EN 901. To include as necessary, relocation of tank and installation, commissioning and maintenance of systems for monitoring and controlling ambient and chemical product temperature to an appropriate set-point within sodium hypochlorite storage rooms, where these have been identified as unacceptable risks in step b(1).
- Produce a schedule of work to address any non-compliance identified in step b(1), including relocation of outdoor tanks, implementation of ambient or chemical product temperature monitoring and control for assets identified in step b(1) prioritised according to risk.
Date: 31 March 2024 - Implement ambient and/or chemical product temperature monitoring for assets identified according to the schedule set out in step b(11)(a).
Date: 31 March 2024 - Design temperature control systems for assets identified in step b(11)(a).
Date: 31 March 2025 - Install, commission and implement temperature control for assets identified according to the schedule set out in step b(11)(a).
Date: 31 March 2026 - Create or update procedure for temperature control, alarms and escalation and brief relevant teams.
Date: 31 March 2026 - Design a solution for any assets which were identified in step b(11)(a), where relocation of the sodium hypochlorite storage is required to achieve compliance with the British Standard.
Date: 31 March 2025 - Install, commission and implement chosen solution for assets identified in step b(11)(a) where relocation of the sodium hypochlorite storage is required to achieve compliance with the British Standard.
Date: 31 March 2028 - Design a solution for any assets which were identified in step b(11)(a), excepting those already covered in steps (b)11(b-g), to achieve compliance with the British Standard.
Date: 31 March 2025 - Install, commission and implement chosen solution for assets identified in step b(11)(a) and step b(11)(h), according to the schedule set out in step b(11)(a).
- Date: 31 March 2028
(c) To audit whether the measures have been effective by the following means:
- Define an audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
Date: 29/02/2024 - 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 sites, 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:
- Provide a progress report annually.
Date: by 31 January each year. - Provide a report detailing the progress with all steps in section b) with date specified as 31 March 2024
Date: 30 April 2024 - Provide a report detailing the progress with all steps in section b) with date specified as 30 September 2024
Date: 31 October 2024 - Confirm design of temperature control for assets identified in step b(11)(a).
Date: 30 April 2025 - Provide a report confirming the implementation of temperature control for assets identified in step b(11)(a).
Date: 30 April 2026 - Provide procedure for temperature control, alarms and escalation and training records.
Date: 30 April 2026 - Confirm solution for assets identified in b(11)(a) where relocation of sodium hypochlorite assets was required to achieve compliance with British Standards.
Date: 30 April 2025 - Provide confirmation of the relocation of the assets identified in b(11)(a).
Date: 30 April 2028 - Confirm solution for any assets to achieve compliance with the British Standard according to step b(11)(g).
Date: 30 April 2025 - Provide a report confirming the implementation of chosen solutions for assets identified in steps b(11)(a) and b(11)(i).
30 April 2028 - Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: 29 March 2024 - Submit any revisions of the audit strategy produced under measure (c)2.
Date: Within 1 month of a revision - 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 - Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
Date: 30 April 2029
Further Details of this notice:
- Any product or substance used as a result of the requirements in this notice must comply with regulation 31.
- Under regulation 28(6) the Inspectorate, on behalf of the Welsh Ministers, may by notice served on the Company, revoke or vary this notice.
- 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 Welsh Ministers
22 December 2023
Reference: DWR-2023-00010