Environment Agency officers, Wiltshire Council and Parish and local councillors attended the Northacre Resource Recovery Centre liaison committee meeting on Tuesday 29 September chaired by Hills Waste Solutions Limited. At the meeting plans were announced to change operations at the site to a Waste Transfer Station.

Hills Waste Solutions Ltd have also confirmed that odour neutralization units have now been installed inside the waste treatment building. However, these are not yet fully operational. We will assess the effectiveness of this measure over the coming weeks. We will continue to review any further odour complaints in conjunction with the findings from our odour monitoring to determine whether this additional measure is delivering the anticipated improvement.

As part of our odour monitoring, we have been using a handheld hydrogen sulphide analyser. This has not detected any hydrogen sulphide in the local area.

Between 3 and 26 August the Environment Agency carried out daily odour monitoring to understand whether the engineering work completed in July has been effective.

Through the first three weeks of August, we continued to see high numbers of reports, and officers found landfill gas odour in residential areas. Although this was rated as very faint to faint intensity it was offensive and pervasive in calm, cool conditions.

Assessment of site monitoring data over the same period has identified periods of low/no suction pressure at the gas engine compound, and corresponding downtime. The cause has been identified as filter blockages in the gas lines. Infinis, the company responsible for the gas engines and maintenance of the gas field, are working to establish the root cause. After this issue was identified, preventative maintenance checks were increased, and normal operation was re-established on 21 August.

We believe the supply interruptions are likely to have increased fugitive emissions from Lower Compton landfill, so we extended our enhanced monitoring period to account for this. Odour reports have since reduced and have stayed low through September (14 reports received to date). In part, this will be due to the change in wind direction; we will carry out monitoring in less favourable conditions to assess the effectiveness of the controls on site.

We continue to monitor progress on site. Our surveys have found the recent permanent capping work is effectively minimising emissions from the western half off cell 26D. Point source emissions have been noted around temporary infrastructure in the eastern half of the cell; although this is to be expected, we are requiring Hills to review their monitoring and remediation methods to ensure these are minimised.

Our Air Quality monitoring team have now produced a second report using data gathered up to 6 August by our mobile monitoring facility in Calne. The full report and summary depending on how you view this update can be found by scrolling down ( if accessing from a mobile device) or to the right if viewing via website. The two documents are entitled : UKSA Lower Compton Landfill PHRA Summary and UKHSA Full PHRA for Lower Compton Landfill.

The latest UKHSA risk assessment concludes there are no exceedances of relevant health guidance values. Although peak concentrations of hydrogen sulphide have reduced since March 2026, the data shows periods where the concentration is above the WHO guideline value for odour annoyance, indicating further work may be needed to achieve permit compliance

Environment Agency officers have continued to monitor for odour in the community, carrying out 24 odour rounds between 3 and 17 August as part of our enhanced monitoring program.

In certain conditions, we found that odour from Lower Compton landfill is still pervasive and although we are substantiating odour at low levels of intensity, further action is needed to minimise odour.

During our most recent inspection of the landfill site on 20 August, we identified several fugitive emission points around temporary gas infrastructure in the eastern half of cell 26D, and Hills are now taking action to resolve these. The recent permanent capping, covering the western half of cell 26D, has reduced odourous emissions from this area.

We are assessing the data we have collected along with data from the gas field and gas engines to determine what further action is required and will continue to monitor odour in the community through August.

We are producing a further air quality assessment based on the data collected from our Mobile Monitoring Facility at Priestly Primary School, covering the period from October 2025 to August 2026. Once complete, we will share this with the UKHSA. Our report and the UKHSA public health risk assessment will be made available on these pages.

We will provide a further update on our monitoring findings and any actions taken by Hills in the next update.

Thank you to all those residents and members of the public who attended the community drop in event on Monday. Staff from the Environment Agency were on hand to answer questions and listen to concerns. Wiltshire Council shared two handouts at the event. These handouts and an update from The Environment Agency can be viewed in the side bar if viewing on the web. If viewing on a mobile please scroll down past the news feed for further details.

This week we began our enhanced odour monitoring programme to assess the effectiveness of the permanent capping works and other measures implemented by Hills to reduce odour from the Lower Compton Landfill site.

As part of this programme, we have been out monitoring odour in the community at all hours, day and night, both in residential communities and near to and within the site boundary. Officers have often attended shortly after odour reports are received from residents to corroborate reports.

Our primary monitoring method is odour assessment, or "sniff testing", undertaken by our trained officers using their noses and recognised FIDOR principals (Frequency, Intensity, Duration, Offensiveness, and Receptor sensitivity). These officers are qualified to detect and assess the presence, character and intensity of odours, providing key evidence to determine whether permit conditions are being met.

We are working closely alongside Wiltshire Council Environmental Health Officers, who monitor odour from a statutory nuisance perspective.

Alongside this, we may also use “Jerome” hydrogen sulphide analysers to support our findings by measuring levels of hydrogen sulphide. Our Mobile Monitoring Facility (MMF) also remains in place and continues to measure ambient air quality in the area.

The Environmental Permit requires the site not to cause odour to escape at a level likely to cause pollution, as perceived by an authorised officer, unless the operator has used appropriate measures to prevent or minimise odour. Officer observations therefore play a vital role in our assessment, particularly as people can detect odour produced by a range of odour producing compounds and can often detect odours at levels below the detection limits of monitoring equipment.

We will provide an update on our enhanced monitoring in the next community briefing.

An Environment Agency officer monitors for odour in Calne - Aug 26

We recognise the frustration caused by the ongoing odour impacts from the Northacre MBT site and therefore we want to provide a further update on our ongoing monitoring and regulatory work.

We are currently receiving an increased number of odour reports from residents in Westbury. As part of our ongoing regulatory response, we are assessing the impact of the recent site shut down period and improvement works. We are gathering evidence both on and off site to understand how effective the changes have been and whether further action is needed. We are considering all available regulatory and enforcement options and will not hesitate to take further action where the evidence supports it. We will share information about any enforcement action as soon as we are able to do so.

We understand that residents have concerns and questions which they would like addressed. To help with this, we are supporting a multi-agency drop-in event organised by Wiltshire Council, giving residents the opportunity to speak directly with representatives from the organisations involved in investigating and responding to the odour issues in Westbury.

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:

• Environment Agency - Site regulation. Contact: wessexenquiries@environment-agency.gov.uk
• Wiltshire Council – Responsible for Environmental Health and statutory nuisance investigations. Wiltshire Council is also the Waste Disposal Authority and is responsible for the management of contracts relating to the treatment of local authority waste, including waste delivered to the Northacre Resource Recovery Centre. For more information: www.wiltshire.gov.uk/article/1833/Smells-and-odours(External link)
• Health concerns, medical advice and Public Health issues – Wiltshire Council advise if you have any concerns about your health, please contact your GP or NHS 111 for individual medical advice in the first instance. If you have any further public health-related queries, you can email Wiltshire Council Public Health at publichealth@wiltshire.gov.uk, who can help direct your query to the most appropriate organisation for a response.
• Hills Waste Solutions – Site operations. Contact: www.hills-group.co.uk/contact-us/

Calne

Representatives from UKHSA joined the Environment Agency and Hills for a visit to Lower Compton Landfill site on Tuesday this week ahead of the public drop in event to view completed capping and gas extraction wells and understand how these works will help reduce odours from the site.

Our public drop in event on Tuesday evening at Calne Town Hall was well attended by members of the local community and local elected representatives. Staff from the Environment Agency. Wiltshire Council, UKHSA and Hills were on hand to answer questions and address concerns. The Environment Agency and Wiltshire Council provided handouts as part of the event that can be accessed to the right of this page under Calne Engagement event 21 July.

The gas extraction wells are being stabilised to ensure they are operating effectively. We will carry out daily monitoring from the start of August to assess whether the work has been effective in minimising odour from Lower Compton landfill.

Hills have issued an update on their website today which can be viewed by accessing the link below: https://www.hills-waste.co.uk/news/lower-compton-landfill-and-northacre-mbt-update

Westbury

After a period of closure for maintenance of one of the cranes in the biohall at Northacre MBT plant in Westbury the plant started accepting waste again on Monday 20 July. Work on the biofilters has been completed and the operator is continuing to make improvements detailed in their action plan. Wiltshire Council will be hosting a community drop in event in mid August and representatives from the Environment Agency will be in attendance to talk to residents and the community and answer questions.

We continue to receive a small number of odour reports and have officers in the community undertaking monitoring to see if the works have made the required improvements to on-site odour control.

We would like to thank the community of Calne, local MP Sarah Gibson and local Cllr Sam Pearce Kearney and residents for attending our multi agency drop in event alongside representatives from UKHSA, Wiltshire Council and the site operator Hills at Calne Town Hall last night to discuss odour issues associated with Lower Compton Landfill site. The Environment Agency shared two written updates with attendees. A link to these documents and a handout shared by Wiltshire Council can be found on the right of this page in the folder Calne Community engagement event. Thank you