After the county council’s development control committee refused planning permission for the quarry between St Albans and Hatfield, on Thursday, the developer said it will consider its options.

Brett Aggregates had hoped to locate a quarry on the former aerodrome site, between Smallford and Ellenbrook, off Hatfield Road, – with plans to extract up to eight million tonnes of sand and gravel over a 32-year period.

Following the meeting, a spokesperson for Brett said: “We’re obviously disappointed with the decision, especially since this site has been identified for quarrying in Hertfordshire’s Minerals Local Plan for several years and recommended for planning approval by council officers.”

The applicant does have the right to appeal against the decision and at the meeting councillors were warned that this could have a financial application.

In refusing the application on Thursday, cross-party councillors pointed to a range of factors – including the impact it would have on the Green Belt, air quality and traffic, as well as the cumulative effect of quarrying in the area and the risk to the bromate plume.

Concerns about the plans had been raised in advance of the meeting by St Albans, Welwyn Hatfield, Hatfield and Colney Heath councils and local residents groups.

Sue Meehan from Ellenbrook Residents Association, who presented a petition opposing the development, highlighted the proximity of the bromate plume to the site and suggested it was “an environmental disaster waiting to happen”.

She stressed that bromate was a known carcinogen – and that this plume was as a result of the worst bromate contamination event in Europe.

“The dangers of this carcinogen are not fully understood and therefore are too big a risk to take.

“The bromate plume is not static and continues to spread ever further from its origin – stretching now to the New River and threatening London water supply.

“The spillage is a very unusual event and no expert knows how it is likely to spread if quarrying occurs nearby.

“No modelling has been undertaken to understand what may happen.

“The developers cannot provide a cast-iron guarantee that bromate will not be drawn on to the dig site. Once the site is polluted it is too late – the damage has been done. And the bromate will take decades to clear.”

Also among those raising concerns about the “colossal plume” was Dr Michael Rivett, director of Ground H2O Plus.

However the report by planning officers – which had recommended that the application be approved – suggested that any risks would be mitigated by the ‘groundwater management plan’.

And in response to councillors’ questions, Keith Spence from the Environment Agency said the risk the quarry posed to the water supply was “exceptionally low” and there was “no data at the moment” to suggest bromate was under the mineral working area.

Speaking in favour of the application at the meeting was Brett Associates’ planning director Simon Treacy, who said the company had a “good track record” – in acting responsibly and delivering quality.

He stressed that the aerodrome site was already earmarked for a quarry in the council’s own minerals plan and that the application had been recommended for approval by officers.

Addressing concerns relating to the plume, he said there had been considerable research and investigation to understand the physical properties of the site – and the extent and behaviour of the plume.

He said that after discussions with the Environment Agency the proposed site was reduced in size so that it sits outside the bromate plume and maintained there has been independent scrutiny of the scheme by both the Environment Agency and Affinity Water.

Addressing other concerns, he said the increase in the number of HGVs – limited to 174 movements a day – was considered “minimal” by the council’s highways officer and was “acceptable” to Highways England and comply with noise limits and air quality impact considered “negligible”.

He added that Brett was “very much committed” to this development and would look to start production on during 2022.

In presenting the application council planning officers suggested that the benefits on mineral extraction outweighed the limited harm the quarry would cause to the Green Belt – and that it met the very special circumstances for development in the Green Belt.