Thames Water Utilities Limited – AMP8 PFAS Strategy
Water Industry Act 1991 (as amended) (“the Act”): Section 19(1)(b)
Reference: TMS-2023-00012
Version: 3
Acceptance Notice:
The Drinking Water Inspectorate, on behalf of the Secretary of State for Environment, Food, and Rural Affairs:
- Is satisfied that Thames Water Utilities Limited “the Company” in supplying water from all water supply systems (raw water assets, water treatment works and treated water assets), which are for the time being listed in the Annex to this Schedule of Works which may be at risk of breaching the wholesomeness and no deterioration standards due to PFAS concentrations. This means that the Company is likely to contravene its duties under Sections 68(1)(a) and 68(1)(b) of the Act and the requirement set in regulation 4(2)(b) of the Water Supply (Water Quality) Regulations 2016 (as amended) (“the Regulations”).
- Has notified the Company on 22 November 2023 that the Secretary of State considering making in relation to the company an enforcement order under Section 18 of the Act.
- Notes that the Company has on 24 June 2024 given a new undertaking under Section 19 (1) (b) of the Act, to take the following steps by the dates shown.
Steps to be taken:
- Ensure that PFAS have been assessed as a hazard, as part of the regulation 27 Risk Assessment for the supply systems listed in the Annex to this Schedule, according to a Drinking Water Safety Plan approach and the Inspectorate’s latest guidance on the risk assessment of individual and total PFAS. Ensure that regulation 28 documents are reviewed (at least annually) and updates provided as necessary.
Date: Ongoing for the duration of the undertaking. - Keep under review the company’s strategy for the protection of public health and for compliance with drinking water quality standards with respect to PFAS.
Date: Ongoing for the duration of the undertaking. - Conduct surveillance, including sampling and analysis for PFAS in line with the Inspectorate’s latest published guidance on PFAS.
Date: Ongoing for the duration of the undertaking. - Produce a prioritised list of sites for additional investigation in step 5. below
Date: 31 March 2025 - Where there are new PFAS detections, or a change in the detected levels, conduct operational monitoring; sampling (and analysis) extended upstream of abstraction points into catchments and sub-catchments, and downstream through different stages of water treatment to the final water sampling location, to identify the source, concentration and fate of PFAS compounds.
Date: Ongoing for the duration of the undertaking. - Following on from step 4, continue to conduct risk-based, enhanced, investigatory sampling (and analysis), where PFAS are detected.
Date: Ongoing for the duration of the undertaking. - Undertake catchment characterisation and identification of PFAS sources (minimum requirements defined in DWI guidance), for example, product usage (existing data available and data gathering), catchment modelling with analysis of weather, surface and groundwater flows, catchment walkovers, identification of high-risk locations.
Date: Ongoing for the duration of the undertaking. - Initiate and maintain regular engagement with relevant stakeholders, to ensure that catchment risk assessments are current.
Date: Ongoing for the duration of the undertaking. - Participate in relevant research and development activities.
Date: Ongoing for the duration of the undertaking. - Where PFAS are detected in a single final water (or downstream treated water) sample, or two or more raw water (water sampled from any point prior to the final treated water point at the water treatment works) samples in a supply system not currently listed in the annex to this undertaking, submit a change request to the Inspectorate to add the supply system to the annex, unless a mitigation plan has already been developed for this supply system.
Date: Ongoing for the duration of the undertaking. - Maintain and continually review the company’s PFAS strategy.
Date: Ongoing for the duration of the undertaking. - For all sources that fall into tier 3, design, develop and implement mitigation to reduce PFAS concentrations in drinking water to at least tier 1 concentrations, with a high priority.
Date: Ongoing for the duration of the undertaking. - For all sources that fall into tier 2, design a proactive and systematic risk reduction strategy which shall include a prioritised mitigation methodology to progressively reduce PFAS concentrations in drinking water.
Date: Ongoing for the duration of the undertaking. - For all sources that fall into tier 1, design a basic mitigation plan, which can be implemented should concentrations increase, or toxicological or other information change that requires mitigation be delivered.
Date: 31 March 2030
Reporting:
- At regular intervals provide the Inspectorate with reports on progress made with carrying out the steps set out in the Action Plan. Reports to include at least the following details:
- All sampling and analysis data from the monitoring of raw and treated water in the supply systems named in the annex.
- Details of the remedial steps that comprise the programme of work including commencement and completion dates for investigations, design, tendering, construction, and commissioning.
- Current state of progress with the steps referred to in 1b) above.
- A summary of progress with the ongoing measures in the steps to be taken section.
- A statement of implications of any slippage of the programme and details of activities planned to bring programme back on target.
- Whether the company has any other reason to believe it may not be able to meet any of the key dates set out in this Schedule of Work.
- The latest version of the company’s PFAS strategy.
- Evidence of no PFAS detections above Tier 1 in a supply system for one year and evidence of the mitigation plan, to remove the supply system from the undertaking annex.
Date: Annually for the duration of the Undertaking. Reporting periods are Jan – Dec. Reports to be submitted by 31 January each year that the Undertaking is in place.
- Submit prioritised list of sites for additional investigation in step 4.
Date: 30 April 2025 - Continue to test at an enhanced frequency for PFAS for a period of 12 months following commissioning of any work associated with the Action Plan to demonstrate the effectiveness of the remedial measures taken.
Date: 31 March 2031 - Provide a final report to the Inspectorate on the efficacy of the steps taken as part of this undertaking. Include, as evidence of closure for this scheme, appropriate documentation to confirm that the actions set out in this Schedule of Work have been completed satisfactorily and that the company’s PFAS strategy is in place.
Date: 30 April 2031
Further Details of this Acceptance Notice:
- The Secretary of State satisfied that Thames Water Utilities Limited 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)(b) of the Water Supply (Water Quality) Regulations 2016 (as amended).
Authorised by the Secretary of State to sign in that behalf
Nicholas Adjei
Deputy Chief Inspector, Drinking Water Inspectorate
25 September 2026
Reference: TMS-2023-00012 v3
Annex A to Schedule for TMS-2023-00012 – Thames Water Utilities Limited
Undertaking in respect of PFAS
Supply System Name | Supply System Reference) |
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Addington Supply system | YTMS1167 |
Ashbury Supply system | YTMS1168 |
Ashton Keynes Supply system | YTMS1169 |
Aylesbury Supply system | YTMS1170 |
Banbury Supply system | YTMS1171 |
Barrow Hill Supply system | YTMS1172 |
Bickley Supply system | YTMS1173 |
Castlewood Supply system | YTMS1174 |
Central Oxford Supply system | YTMS1175 |
Chelsfield Supply system | YTMS1176 |
Chessington Supply system | YTMS1177 |
Chigwell Supply system | YTMS1178 |
Chinnor Supply system | YTMS1179 |
Cirencester Supply system | YTMS1181 |
Cleeve Supply system | YTMS1182 |
Cockfosters Supply system | YTMS1183 |
Compton Supply system | YTMS1184 |
Cranleigh Supply system | YTMS1185 |
Crouch Hill Supply system | YTMS1186 |
Crystal Palace Supply system | YTMS1187 |
Deddington & Bicester Supply system | YTMS1188 |
Ealing Supply system | YTMS1189 |
Eltham Supply system | YTMS1190 |
Epsom Supply system | YTMS1191 |
Farnborough Supply system | YTMS1192 |
Farningham Hill Supply system | YTMS1193 |
Finsbury Park Supply system | YTMS1194 |
Fish Hill Export Supply system (Severn Trent) (TW Supply system: North Cotswold) | YTMS2000 |
Guildford Supply system | YTMS1195 |
Hampstead Supply system | YTMS1196 |
Hampton 30/36 Supply system | YTMS1197 |
Hampton 42 Supply system | YTMS1198 |
Hampton Country Supply system | YTMS1199 |
Henley Supply system | YTMS1200 |
High Beech Supply system | YTMS1201 |
Hoddesdon Supply system | YTMS1202 |
Hornsey Lane Supply system | YTMS1203 |
Hungerford Supply system | YTMS1204 |
Kempton 48 Supply system | YTMS1205 |
Kent Wells (IWNL) (TW Supply system: Multiple) | YTMS3021 |
Knockholt Supply system | YTMS1206 |
Ladymead Export (Affinity) (TW Supply system: Guildford) | YTMS2009 |
Maiden Lane Supply system | YTMS1207 |
Marlborough Supply system | YTMS1208 |
Mill Hill Supply system | YTMS1209 |
New Cross & Riverside Supply system | YTMS1210 |
Newbury Supply system | YTMS1211 |
North Cotswolds Supply system | YTMS1212 |
Norwood Supply system | YTMS1213 |
Nunhead Supply system | YTMS1214 |
Oxleas Wood Supply system | YTMS1215 |
Putney Supply system | YTMS1216 |
Quainton Export (Anglian) (TW Supply system: Aylesbury) | YTMS2001 |
Queen Street, Braydon Export (Wessex) (TW Supply system: Ashton Keynes) | YTMS2003 |
Reading Supply system | YTMS1217 |
Russell Hill Supply system | YTMS1218 |
Sewardstone Supply system | YTMS1219 |
Shootup Hill Supply system | YTMS1220 |
Slough Supply system | YTMS1221 |
Southfleet Supply system | YTMS1222 |
Surbiton 30 Inch Supply system | YTMS1224 |
Swindon North Supply system | YTMS1225 |
Swindon South Supply system | YTMS1226 |
Thame Supply system | YTMS1227 |
Tring Supply system | YTMS1229 |
TWRM (IWNL) (TW Supply system: Multiple) | YTMS3022 |
Wantage Supply system | YTMS1230 |
Westerham Supply system | YTMS1231 |
Witley, Chiddingfold & Dunsfold Supply system | YTMS1232 |
Witney Supply system | YTMS1233 |
Woodford Supply system | YTMS1234 |
Wycombe Supply system | YTMS1235 |