South East Water Limited – Forstal WTW PFAS

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

Reference: SEW-2026-00006

Version Number: 1

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:

Asset Name	Reference
FORSTAL GROUNDWATER CATCHMENT	C321C2
FORSTAL TREATMENT WORKS	T321T02
FORSTAL SUPPLY SYSTEM	Y321T02

Table 1: List of assets affected and associated reference numbers

Details of this Notice:

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 01 October 2025, which states that there is or has been a significant risk of supplying water from Forstal WTW (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 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
Potential risks to drinking water quality and non-compliance with the Water Supply (Water Quality) Regulations.	Sum of PFAS	C321C1-CATCHMENT-F366
	Total PFAS	C321C1-CATCHMENT-H067
	PFOS	C321C1-CATCHMENT-F033A
	6-2 FTSA; THPFOS	C321C1-CATCHMENT-F299
	PFecHS	C321C1-CATCHMENT-F322
	PFPeA	C321C1-CATCHMENT-F329
	PFHxA	C321C1-CATCHMENT-F333
	PFHxS	C321C1-CATCHMENT-F338
	PFBA	C321C1-CATCHMENT-F340

Table 2: Table of the hazards, hazardous events, and/or parameters covered by this Notice, including the Hazard I D numbers and the description of risks.

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:

Continued implementation of raw water management strategy to ensure treatment processes are not compromised and forced to operate outside operational limits.
Date: Ongoing for the duration of this Notice
Evaluate and determine the most suitable method to blend the source waters to reduce the PFAS concentration in the final water accordingly to ensure compliance with the regulations.
Date: Ongoing for the duration of this Notice
Monthly water sampling of raw and final waters for PFAS.
Date: Ongoing for the duration of this Notice
Continuation of catchment management working with stakeholders to reduce input from sources, understand activities contributing to PFAS in catchment and put in place and maintain appropriate mitigations for areas at high risk.
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:

Design and develop mitigation measures to reduce PFAS concentrations in drinking water to at least tier 1 concentration.
Date: 31 March 2029
Complete the Installation and commissioning of the new treatment process at Forstal Treatment Works to mitigate the risk of PFAS. Commissioning must include the following to allow for the changes made:

An appropriate maintenance regime for PFAS treatment;
Full integration of the new processes into the site control and monitoring systems;
Updating of the Site Specific Disinfection Policy and any associated site-specific procedures;
Updating of Site Operating Manual and removal of all out of date material from circulation; and
Provide adequate training to operators as part of the commissioning process and for any revision of the Site Operating Manual completed under (b)2.
Date: 31 March 2032

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: 31 August 2026
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 TREATMENT WORKS, 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.
Submit a report outlining the chosen solution designed under measure (b)1.
Date: 30 April 2029
Submit a report on completion of the installation and commissioning of the chosen treatment option, with an updated site-specific disinfection policy, an updated site operating manual and evidence of completion of training required as specified in measure (b)2.
Date: 30 April 2032
Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: 30 September 2026
Submit any revisions of the audit strategy produced under measure (c)2.
Date: Ongoing for the duration of this Notice
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 2033

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 Secretary of State, 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).

Signed

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
25 June 2026
Reference: SEW-2026-00006

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