Concerns about the impact underground pollution is having on the county’s water have been raised.

An underground ‘bromate plume’ is reported to have been spreading eastwards from a site in Sandridge for a number of years.

Cllr Margaret Eames-Petersen told a meeting of Hertfordshire County Council on March 26 that efforts to clean it up have not worked.

She highlighted concerns about the impact the plume was having on groundwater – which she believes could become worse should an adjoining Hatfield site be quarried.

And she called for the county council’s executive member for public health and prevention Cllr Tim Hutchings to write to Secretary of State Michael Gove to ensure sufficient funds were available for further work to clean it up.

Labour councillor Cllr Eames-Petersen told the council: “This is now recorded as the worst bromate contamination in Europe with serious implications for drinking water in Hertfordshire and in London.”

Cllr Eames-Petersen told councillors that the plume had spread from Sandridge, through Hatfield and had continued eastwards towards the New River and the River Lea.

She said data published earlier this year suggested 27 out of the 45 monitoring boreholes are now contaminated above the World Health Organisation safe threshold.

Cllr Eames-Petersen has already said she is against plans to quarry minerals from the Hatfield Aerodrome site, which is identified in the council’s draft minerals plan, amid fears the excavation could impact on the spread of the leak.

But at the meeting she stressed this was an issue about the quality of drinking water in the future, not the the possible siting of a quarry.

In response to Cllr Eames-Petersen’s concerns, executive member for public health and prevention Cllr Tim Hutchings said he did not accept the “premise”.

But he committed to talk the the director of public health to see if what the councillor was saying “stands up”.

In relation to the impact quarrying at the Hatfield Aerodrome site could have on the bromate plume – and drinking water – Cllr Hutchings repeated an earlier written response on the issue.

This response suggested the minerals plan would be reviewed if evidence suggested contamination made the Hatfield Aerodrome site unworkable.

It read: “In terms of the minerals local plan, if it were to be proved that the whole resource was unworkable due to the presence of contamination of the water source then the minerals planning authority would need to reassess other potential sites to meet the needs of the area – this has not proved to be the case.”

Cllr Hutchings said that at the moment the case was unproven. But he said that if further  information came to light he would be happy to look at it.

Following the meeting, a spokesman for the Environment Agency said that Affinity Water and Thames Water had been treating contaminated water from Hatfield before sending it to the main sewer since 2006.

But he said that although the agency did regulate certain types of contaminated land, they did not undertake ‘remediation’ where the party responsible was identified and had the capability.

With regard to the quarry plans, he said they had asked the county council to secure a water management plan from developers, to ensure any risks to ground water and surface water were considered and managed.