Public demand answers on PFAS in Harefield water source

Residents of Buckinghamshire and West London are calling for further investigation into a common PFAS previously detected at one of the region’s pumping stations.

If you get off the 724 bus at Station Parade in Harefield, in the London Borough of Hillingdon, the short walk up Moorhall Road will take you over the River Colne, under a viaduct of HS2 and past Blackford Public Water Source (PWS) which is scheduled to resume its pumping of drinking water from the Mid Chilterns Chalk Aquifer in the next few months. 

For many residents of the Colne Valley, this could be their area’s entire recent history as a five-minute walking tour.  

Like many other communities in England, the construction of the HS2 railway has been a flashpoint. Controversy over changes to the line’s route – thanks to the lobbying of a former MP – to tunnel under the southernmost part of Buckinghamshire was followed by a local campaign against the risk of contamination of water sources by construction-related pollutant, chromium-6, a toxic chemical made famous by the ‘Erin Brockovich’ feature film. 

Now, Affinity Water, the local water company, has applied to delay the re-opening of Blackford PWS. 

Will Blackford PWS remain closed? 

In 2019, as the construction of HS2 was getting underway, Affinity Water, the licensed drinking water supplier to extract at Blackford PWS applied to use their right to vary their license (28/39/28/0480) for abstraction to enable the temporary closure of Blackford PWS as a precaution against: “risks to water quality which cannot be established until HS2 works commence.”  

Any shortfall in supply would be made up by increased abstraction from other sites. This arrangement came into force in May 2021 and was due to come to an end in March 2025. 

However, in October 2023, the Drinking Water Inspectorate, a regulator under the Department for Environment, Food and Rural Affairs, issued a notice to the drinking water supplier regarding what they claimed were unsafe levels of PFOA, a PFAS, in drinking water drawn from Blackford. 

While this is unlikely to be linked to the construction of HS2, it may be linked to sewage discharge into waterways, as PFAS pollution found in wastewater remains unregulated. 

Long-chain and short-chain PFAS: what is the difference?

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals with exceptional chemical stability and unique characteristics, including resistance to water, oil, and heat. They are used extens... Read More

A set of results from a 30-day testing programme in 2024, made publicly available as part of a Freedom of Information request (details of which can be found here), showed considerable improvement.  

Nevertheless, the drinking water supplier has applied to extend the current arrangement beyond the original March deadline this year, raising concerns from residents that the PFOA problem persists. 

As a result, local activists have called on the Environment Agency to step up its monitoring of the area’s water quality and to identify sources of pollution, as the local water supplier is not responsible for waterways that feed the Mid Chilterns Chalk Aquifer or other activities that risk its contamination with PFOA. In fact, Affinity are acting in the interest of public health by taking these precautions.

What residents want to know is what's going on and what can be done about it.

How citizen science is filling the gap 

In 2022, an analysis by Prospect, a trade union whose members include managers and engineers in the public sector, suggested that the budget allocated to the Environment Agency had been halved since 2010.

As a result, getting to the bottom of emerging problems is usually limited to the writing of FOI requests – that is, unless local residents can get their hands on their own monitoring equipment. 

DEFRA to Use River Pollution Fines to Beat Budget Cuts

When it comes to river pollution, the Department for Environment, Food and Rural Affairs (DEFRA) has become synonymous with ineptitude and delay. Figures released for 2020 indicate that there was... Read More

In this case, empowering citizens to conduct their own monitoring (in conjunction with specialists) may help to ease concerns by clarifying the nature of the problem – or even, to clarify whether there’s still a problem.  

Speaking to Envirotech Online at a public meeting on the banks of the Grand Union Canal near Blackford PWS, local activist and member of Stop HS2 Sarah Green said: “If we had more citizen science that could monitor for these 'forever chemicals' and we could work alongside the Environment Agency to track down the source of this contamination.” 

Such citizen-led monitoring can ultimately lead to more effective application of existing regulations as well as engender greater trust between authorities and the public.  

Another attendee and member of Stop HS2, Mark Keir was emphatic: “Citizen science is critical now. It’s not the only tool but it’s a very, very important tool.” 

The Environment Agency is currently accepting public comment on the application.  

By Jed Thomas and Alan Booth

How sewage sludge in agriculture contaminates crops with PFAS

Per- and polyfluoroalkyl substances (PFAS), commonly referred to as "forever chemicals," have garnered widespread attention due to their persistence in the environment and potential to harm human h... Read More