The Environment Agency says it is considering enforcement action against Hills Waste after identifying that its waste site in Westbury is “currently not compliant with the conditions of its environmental permit” amid ongoing odour complaints.
The announcement follows an increase in recent reports from residents about an odour, often referred to as the ‘Westbury Whiff’, coming from the Northacre Mechanical Biological Treatment plant on Stephenson Road operated by Hills Waste Solutions.
Odour issues at the site have been the subject of complaints from residents for a number of years, with no prosecution action taken following a previous breach in 2021.

On 5th June, the Environment Agency said the increase in odour reports had been linked to a fault in the site’s biofilter system, which is used to control odours. Residents were told that Hills had replaced a faulty sensor, installed a backup system and regenerated the biofilter to restore performance and reduce odour.
However, in a further update on 19th June, the Environment Agency said the biofilter was still not operating effectively after a fault developed in a newly installed moisture control sensor, causing the system to become too wet and reducing its effectiveness.
In a statement, the Environment Agency said, “While a back-up system enabled the issue to be identified quickly, we recognise that any increase is concerning and understand the frustration this causes within the community. We have required Hills to take action to rectify this as quickly as possible.
“We have independently observed an increase in odour this week, which we attribute to these ongoing biofilter failures. The odour our officers are detecting is primarily that associated with general household waste and not hydrogen sulphide that is present at other waste sites.
“Following our investigation and direct engagement with Hills, we have formally identified that the site is currently not compliant with the conditions of its environmental permit. We have made clear to the operator that this situation is unacceptable and have required immediate corrective action.
“As a result, we are considering enforcement action and have instructed Hills to resolve the issues with the biofilter as a matter of urgency. Our priority is to ensure the operator meets its legal obligations and that the impact on the community is minimised.
“Our officers have been proactively monitoring conditions on site and are continuing to respond promptly to odour reports. This increased level of oversight will continue until we are satisfied that the issues have been fully resolved and that control measures are working reliably.
“We want to reassure residents that we are holding the operator to account and taking firm regulatory action to resolve the situation. Your reports play a vital role in supporting this work, and we encourage you to continue reporting any odour incidents.
“We appreciate the community’s continued patience and will provide further updates as soon as there is meaningful progress.”
A spokesperson from Hills Group said, “We continue to work with the Environment Agency on issues related to the biofilter.”
To report a smell to the Environment Agency, visit gov.uk/report-smell or call 0800 80 70 60.
Pictured: Environment Agency staff monitoring odour in Westbury





