A decision on a proposed quarry on the site of the former Hatfield Aerodrome is now in the hands of a planning inspector.

Brett Aggregates want to extract up to eight million tonnes of sand and gravel from the former aerodrome site – which sits between Smallford and Ellenbrook – over a 32-year period.

An application by the company – which included a new access onto the A1057, an aggregate processing plant, a concrete batching plant and other ‘supporting facilities’ – was refused by Hertfordshire County Council, last September.

And after an appeal was lodged against that decision, the proposals have been the focus of an eight-day planning inquiry, which began last month.

Evidence for and against the proposal has been presented on behalf of Brett and the county council, as well as London Colney Parish Council, Ellenbrook and Smallford residents’ associations.

And during the hearing, Brett asked that ‘changes captured within’ an alternative application – submitted earlier this year – be considered by the inspector.

On Monday the inquiry was formally closed, after ‘closing statements’ and applications for costs were made at a virtual hearing.

And planning inspector John Woolcock will now publish a decision on the proposals at a later date.

At the final session of the hearing, Cllr Peter Cook from London Colney Parish Council argued against substituting the four changes from Brett’s 2021 application at inquiry stage.

Unlike the first, the newer application does not include the erection and operation of a concrete batching plant.

It also stipulates that there would be no pumping from the ‘lower mineral horizon’ and that the distance between extraction in that horizon and the bromate plume is increased, from 50m to 100m.

And in addition the access road from the quarry entrance would be moved by five metres to the east, in order to allow for additional acoustic screening.

That application has not yet been determined by Herts county council’s planning process, with public consultation still ongoing at the start of the inquiry.

And Cllr Cook said that substituting the changes at inquiry stage – before the application had been considered through the planning process – would take away the right of the public to make contributions to democratic decision making.

At the final day of the hearing, Cllr Cook also pointed to the impact the quarry would have on the Green Belt and the cumulative impact of quarrying.

He highlighted the proximity of the bromate plume – suggesting that concerns had not been properly addressed and that the ‘risk of bromate to public health is too high’.

And he said: “We are disappointed the EA, Affinity Water, the county council seem almost oblivious to the real risk of contamination to Hertfordshire’s residents.

“However slight, if proven in due course all four will have responsibility for and liability to the public.”

Meanwhile, David Forsdick QC, acting for the county council, also argued against the proposal, that the council had refused.

He accepted that the site had been allocated for mineral extraction for a number of years.

And once the ‘hydrogeology issue’ was resolved, he accepted that permission would need to be granted for a scheme.

But he said that any scheme should minimise the impact on the openness of the Green Belt and maximise the quality and quantity of public access during the work.

At the hearing he acknowledged a number of concessions had been made.

And he suggested consideration of the ‘substitutions’ made by Brett was ‘to all intents and purposes to substitute the 2021 application proposals into the 2016 appeal’.

Addressing the proposed changes, he pointed to the ‘complete turnaround’ with regard to ‘pumping’ of water from the lower mineral horizon’.

He pointed to assurances regarding the bromate plume.

And he said that if there were to be a ‘no pumping’ condition – and triggers for interventions were imposed – there was no reason to refuse based on groundwater facts or safety of public water supply.

He also said the inclusion of the concrete batching plant in the initial proposal was ‘flawed’.

And he said there was no scheme of drawings that showed what was now proposed.

“Despite the very significant concessions made during this appeal, they are not reflected in any plans sought to be approved and it is assumed by Brett that an adequate response to them can be retrofitted into the set parameters fixed by the plans to be approved,” said Mr Forsdick.

“That is the wrong way round and does not demonstrate minimisation of impacts or maximisation of quality and quantity of access.”

Making his final case, Richard Kimblin QC, for Bretts, highlighted the inclusion of the site in the county council’s minerals local plan – identifying it as a site where ‘permission is likely to be forthcoming’.

He suggested, ‘the scheme is a well-designed scheme within an area which the Council has long maintained to be a suitable and sustainable location to meet its mineral need.’

He said Brett had since undertaken not to construct the concrete batching plant.

But he said the size of the processing plant was essential to include sufficient circulation space for machinery and pedestrians – ‘essential to safe operation and in order to prevent workplace accidents’.

With regard to issues around the views into the plant from the south, he said some ‘screening’ would be required – which could be addressed with planning conditions.

He also suggested that concerns relating to the position of the bromate plume had been addressed during the inquiry.

He said the Environment Agency, Affinity Water, HCC and Brett now agreed there was ‘no plausible scenario under which bromate could migrate onto the proposed quarry at sufficient concentrations to cause a long term problem’.

And he highlighted a number of conditions that could be imposed to avoid unacceptable effects upon groundwater.

He pointed to the need for a sufficient supply of minerals, to provide the infrastructure, buildings, energy and goods that the country needs.

And in the consideration of the appeal, he suggested great weight should be given to the benefits of such mineral extraction, including to the economy.

In his closing statement, he again made the case for the changes included in the latest 2021 application to be considered.