We continue to identify unacceptable levels of odour beyond the boundary of the Northacre MBT facility, Westbury. We recognise the significant impact this is having on residents and understand the frustration caused by these ongoing odour issues.

Last week, we engaged with the site operator, Hills Waste Solutions and Wiltshire Council to reduce odour emissions from the site. We have required the operator to implement additional measures to reduce the impact of operations on the surrounding community. As an immediate step, we have required a reduction in the maximum quantity of waste accepted at the facility from 300 tonnes per day to 215 tonnes per day. We consider this restriction necessary to help reduce odour emissions while further operational improvements are implemented and assessed.

Wiltshire Council has a statutory responsibility to collect household waste across the county. This decision has therefore been taken following discussions with Wiltshire Council to ensure the greatest possible reduction in odour impacts to residents of Westbury while minimising disruption to essential public services. Due to the location of the facility and the logistics of Wiltshire Council's waste management network, it is not currently feasible to divert greater quantities of waste away from the site without creating a substantial risk of disruption to household waste collections and the accumulation of waste elsewhere in the county.

We want to reassure residents that this reduction is not the limit of our regulatory response. If the measures currently being implemented do not deliver a sufficient improvement in odour conditions, we will not hesitate to require further reductions in waste inputs and consider additional regulatory action where appropriate.

Alongside the reduction in waste tonnages, Hills Waste Solutions is carrying out further improvements within the facility. These include enhancements to deodorising systems and the installation of additional localised odour extraction measures designed to reduce emissions arising from site operations.

We will continue to closely monitor conditions at and around the site to assess the effectiveness of the measures. If odour impacts do not reduce sufficiently, we will ask Wiltshire Council to consider further actions to maintain household waste collection services while enabling additional reductions in waste tonnages received at the site

We would like to remind residents that next week, we are supporting Wiltshire Council with a community drop-in on Mon 17 Aug 26 (further details below), where we invite you to come and discuss the ongoing odour issues relating to the Northacre MBT facility with representatives from the organisations involved.

The Environment Agency remains committed to protecting people and the environment. We will continue to work with Hills Waste Solutions, Wiltshire Council and other relevant organisations to secure lasting improvements and reduce the impact on the local community.

Community Drop-in Event 17 August 2026

Westbury: Northacre MBT Odour Response Drop-in Event

Date: 17 August 2026
Time: 5:30pm-7:30pm (drop in anytime)
Location: The Laverton, 10 Bratton Rd, Westbury, BA13 3EN

Representatives from multiple agencies will be available to answer questions and provide information:

As part of the Environment Agency's requirement for the operator to implement an action plan to reduce odour levels, officers visited the Westbury site this week to review the works completed during the closure period and discuss progress with the operator.

As outlined in our previous update, Hills temporarily closed its Northacre Mechanical Biological Treatment (MBT) facility in Westbury for two weeks to carry out maintenance on one of the biohall cranes. This work has now been completed, and Hills has advised us that the facility is expected to reopen on Monday 20 July, with waste acceptance resuming from that date. We will continue to complete site inspections and respond to odour reports to ensure that this work has reduced odour levels.

Further information from Hills about this decision is available here: https://www.hills-waste.co.uk/news/northacre-mbt-lower-compton-landfill-and-ukhsa-report

During the closure period, Environment Agency officers have continued to investigate odour reports and have met with local residents to better understand their concerns. We would like to clarify that the odours reported in Westbury are not linked to hydrogen sulphide (H₂S), which is the issue currently being experienced by residents in Calne. The odour that can be smelt in Westbury is most likely to be associated with volatile organic compounds, volatile fatty acids, alcohols, aldehydes and ketones. This is typical for "bottom of a bin" odour that is being reported.

We have also received reports of increased fly activity during the plant closure. At present, we cannot specifically attribute this to the facility. Factors such as weather conditions and nearby livestock may be contributing to the presence of flies.

We recognise the impact that odour and environmental concerns can have on local communities and understand the frustration they can cause. We remain committed to engaging directly with residents in Westbury and are working with Wiltshire Council to arrange a community engagement event in August, where people will have the opportunity to discuss their concerns and hear updates from the agencies involved.

Environment Agency officers have been on site at Lower Compton Landfill this week to review the operator's progress against the improvement action plan we requested.

Following the completion of capping works last week, drilling of six additional landfill gas wells began on 13 July and is scheduled to be completed on 17 July (see image). These permanent vertical gas wells have been installed through the newly capped area and are expected to improve gas capture and further reduce emissions from the site.

As with any new system, there will be a short period of stabilisation while the equipment becomes fully operational.

The new wells are connected to the landfill gas management system, allowing methane and other landfill gases to be actively extracted and controlled. To assess the effectiveness of these measures, experienced Environment Agency officers will begin air quality monitoring in August. This monitoring will help determine whether the new infrastructure is reducing odours and improving gas collection.

The Environment Agency will continue to closely monitor the site and carry out regular inspections to ensure emissions remain effectively controlled.

Should odour issues continue following the August monitoring period, we will require Hills Waste Solutions to review and update its action plan to identify any further measures needed.

Separately, works at the Northacre Mechanical Biological Treatment (MBT) facility in Westbury have now been completed. Hills has confirmed that the facility is scheduled to reopen on 20 July, meaning waste will no longer need to be redirected to Lower Compton Landfill.

We look forward to welcoming residents and members of the community to our multi-agency drop-in event on Tuesday 21 July 2026, from 4pm to 7pm at Calne Town Hall. This is an opportunity to discuss the recent UKHSA air quality assessment, capping works, gas wells and ongoing activities at the site with representatives from the Environment Agency, UKHSA, Wiltshire Council and Hills Waste Solutions.

We look forward to seeing you there.

We wanted to share information to address some of the feedback and comments received from residents and the community around the location of the Environment Agency’s monitoring facility in Calne following publication last week of the UK Health Security Agency (UKHSA) Public Health Assessment. The Environment Agency will be able to address any further questions at the public drop in engagement event at Calne Town Hall on 21 July 4-7 pm.

The primary purpose of the Environment Agency’s monitoring is to support our regulatory responsibilities and assess compliance with the site’s Environmental Permit. The purpose of an Environmental Permit is to ensure waste activities are carried out in a way that protects the environment and people. More information about environmental permits can be found here: Waste: environmental permits - GOV.UK.

The Environment Agency understands why residents may want air quality monitors located in different parts of the community. However, the placement of air quality monitoring equipment involves balancing scientific, practical and operational considerations. While some residents may feel the monitor is not in the ideal location, our assessment is supported by analysis of odour reports received from the community.

The monitor’s current location at the school was chosen following an assessment of a range of factors. The monitoring unit is a large, specialist piece of equipment that requires a secure location, a reliable power supply, compliance with strict electrical safety requirements, and permission from the landowner. Suitable sites that meet all of these requirements can be difficult to secure.

When selecting a monitoring location, it is important that we collect data that is representative over time, rather than continually moving equipment in response to individual reports or changing weather conditions. If the monitor were regularly relocated to follow where odours are being reported on a particular day, we would risk "chasing the plume" rather than gathering robust, representative data about air quality and potential exposure within the wider community.

By keeping the monitor in one location for an extended period, we are able to capture a range of operating conditions, weather patterns, wind directions, temperatures and atmospheric pressures. This provides a more complete picture of air quality over time, allowing us to assess periods when emissions may increase, decrease or change direction. Longer-term monitoring therefore produces data that is more reliable and representative than a series of short-term measurements taken at multiple locations.

We recognise that no single monitoring location will satisfy everyone's expectations, and there is always an element of compromise in the siting process. However, based on the available evidence and the practical constraints involved, we are confident that the current location at the school provides an appropriate balance between scientific robustness, operational practicality and the need to obtain meaningful monitoring data.

The mobile monitoring facility (MMF) located at the school was not deployed for public health investigations and is not the primary source of evidence used to determine permit compliance.

The most important evidence comes from trained Environment Agency officers carrying out odour assessments within the community. These officers are qualified to detect and assess the presence, character and intensity of odours, providing the key evidence used to determine whether permit conditions are being met. Data collected by the MMF is used to complement and support this officer-based evidence.

The Environmental Permit does not have specific limits for air pollutants. Instead, it includes a more powerful condition that requires the site “not to cause odour to escape the site at a level likely to cause pollution as perceived by an authorised officer”. As a result, officer observations are an important part of our assessment because people can often detect odours at levels below the detection limits of monitoring equipment.

The Environment Agency does not have the powers or specialist public health expertise to investigate potential health impacts on local communities. Responsibility for assessing and responding to public health concerns sits with Wiltshire Council and the UK Health Security Agency (UKHSA). This includes the potential for extra monitoring in the community. To support their work, the Environment Agency has shared the monitoring data collected by the MMF with the UKHSA who completed their public health risk assessment which can be accessed here UKHSA Full PHRA for Lower Compton Landfill

We look forward to welcoming you to our event next week.

Annotated Mobile Monitoring Facility