Cambridge Water errors led to toxic water, report says

Toxic water was caused by "incorrect assumptions, errors, delays, and incorrect information" from a water company, a report said.

Cambridge Water supplied Cambridgeshire homes from an aquifer containing high levels of PFAS (polyfluoroalkyl and perfluoroalkyl substances).

The Drinking Water Inspectorate (DWI) said it meant confidence in the supplier "was brought into question".

The firm said the contaminants did not reach customers - and has apologised.

More than 1,000 customers in Great Shelford and Stapleford were said to have been affected by the contaminated water from the Duxford aquifer, the report added.

The water was said to contain four times the legal limit of perfluorooctane sulphonate (PFOS).

PFOS is part of the wider family of PFAS substances.

The report from the inspectorate said the contamination came from "firefighting activity where PFOS was commonly used in firefighting foam on aircraft and the airfield" in Duxford.

Cambridge Water was "not responsible for this ground contamination but was aware of its presence in historical data", the inspectorate said.

The company blended water from Duxford with water from another source "incidentally reducing the level of PFOS in supply".

The report said the company notified the DWI on 8 February 2022 "and as a result of a media article which appeared in the the Guardian on the same day".

It said it had already issued precautionary guidance on PFOS - and more widely PFAS - in January 2021.

But the report said following that guidance, the actions by Cambridge Water "were far short of the minimum expectations of a water supplier because of incorrect assumptions, errors, delays, and incorrect information which allowed the inadequate blending arrangement to continue to June 2021".

The inspectorate served the company with "a precautionary prohibition notice to protect water quality based upon the potential to fail wholesomeness" on 21 February 2022.

Cambridge Water said the supply from Duxford "has been isolated from our system so it is not supplying any water" while improvement works took place.

"We apologise to our customers for the errors that were made at the time," it said in a statement.

The company said it had "already taken steps to improve our processes" and would "take forward" additional measures in the report.

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