Update

We are continuing to investigate the recent and significant increase in odour complaints from residents in Calne.

While landfills and other waste activities will always generate smells, the impact on people living near them should be minimal. It is clear from the recent reports that the current controls in place at Lower Compton landfill are not performing as expected and are therefore inadequate.

We recognise the impact this is having on the community and are working closely with Wiltshire Council and the UK Health Security Agency (UKHSA) to identify specific odour sources and ensure action is taken to bring odour back to minimal levels.

This briefing is an update on the progress of our investigations with Hills Waste Solution (the operator of Lower Compton Landfill) and actions taken by them in response to recent odour reports.

Odour reports have increased significantly since the beginning of 2026, with 16 reports in late January, 101 in February, and over 1,000 in March. This trend has continued into April, with 726 reports to date.

We have determined that the initial increase in reports at the end of January and into February was likely caused by the installation of additional gas collection wells in the operational area of the landfill, which involved digging into recently deposited waste. However, we have continued to receive reports since this work was completed on 6 February.

Our recent inspections have found the main source of odour in the area is the current open landfill cell.

We are continuing to carry out offsite odour assessments, including early morning and evening visits when odours are commonly reported.

Our ambient air monitoring station has been in place in Calne since October 2025 and has now collected sufficient data on levels of Hydrogen Sulphide, Methane and Particulates in the community to produce an interim report. The data will now be validated and shared with UKHSA so they can provide updated public health advice; we will publish this report with the dataset once it is completed. Our ambient air station remains in place, and we have extended the study due to the ongoing reports of odour in the community.

Our officers have been out in the community, and have undertaken 22 odour inspections during March and 23 so far in April. These often occur in the early morning and late evening when odour is most noticeable in certain weather conditions.

We have identified landfill gas odour in residential areas and have traced this to Lower Compton landfill, specifically Cell 26D. We have also found odour from other sources, such as land spreading, grounds maintenance, and other waste activities, but have identified Cell 26D as the primary source of landfill gas odour.

On-site inspections

Following the strong odour identified in recent inspections, we have required Hills to provide a short to long-term action plan identifying how they will minimise odour and emissions from this area, and the likelihood of reoccurrence in future cells.

We are currently discussing the scope and timescale of the actions required with Hills. However, actions already underway include:

Short term actions:

• Change in material used as cover in the operational area from ‘trommel fines’ to soil. Work has been ongoing since 27 March to cover the operational area with soil, and we expect this action to be completed this week.
• Ongoing review of temporary gas collection within the cell and installation of further gas collection wells.
• Ongoing monitoring to check the effectiveness of the cover being placed

Medium term actions:

• Permanent capping of the current operational area. This has been brought forward from July and will now start in early May. The work is expected to be completed within 13 weeks. Permanent capping and installation of permanent gas collection infrastructure is the best long-term solution to minimise odour and emissions.

We are closely monitoring these works as they progress and are now undertaking weekly inspections of the site.

There are a number of factors likely to have influenced the increase in odour, and we are considering these when requiring the site’s management systems to be revised.

Previous inspection reports are available online via: environment.data.gov.uk/public-register/view/index. The standard timescale for our most recent reports to be made available on the public register is 28 days after issue. However, there may be a delay if a report is subject to a regulatory appeal.

Summary of next steps

• It is Hills Waste Solutions responsibility to improve their air quality issue.
• We will continue increased offsite odour monitoring to determine whether conditions improve.
• We will carry out weekly inspections of Lower Compton landfill as improvements are made to ensure they are effective, including further thermal imaging surveys to check for potential emissions from the operational area and surrounding cells.
• UKHSA will review the monitoring data from the ambient air unit once the report is complete. The data will then be validated and the UKHSA will provide updated public health advice.
• Regulatory measures will be considered if improvements are not delivered at pace, these can include: enforcement notices, restricting waste inputs, or other enforcement in line with the Environmental Permitting Regulations.

Our position is clear: odour impacts at this level are not acceptable, and the operator must act quickly to resolve the issues.

We will be uploading further information regarding the site and current odour issues over the next few weeks.

Please continue to report odour you believe is coming from activities we regulate. Although we cannot provide individual feedback, these reports are vital for our investigation.

24‑hour incident hotline: 0800 80 70 60 or via the online GOV.UK service: Report a smell from a waste facility, industrial site or farm in England - GOV.UK

We are investigating the recent and significant increase in odour complaints from residents in Calne.

In March, we received over 1,000 reports of odour, with the majority of these being reported between the 19 and 23 of March.

We fully recognise how intrusive persistent odour can be and want to be clear that the odour levels currently being experienced are unacceptable.

Our officers have been out in the community, including early in the morning and late in the evening when odour seems to have been most noticeable. At times, we have been able to identify landfill gas odour and have traced this to Lower Compton landfill.

The high volume and persistence of reports indicates that odour management on site at Lower Compton landfill is still not optimised, and further regulatory intervention is required. We will continue to work to ensure that additional corrective measures are put in place to minimise the likelihood of further recurrences.

Our ambient air monitoring station is collecting continuous data on levels of Hydrogen Sulphide, Methane and Particulates.

We are looking at all aspects of the Lower Compton landfill site. Our main focus is on the current cell 26D, due to the change in nature of the waste inputs in this cell.

Until recently, the measures Hills had put in place were minimising odour from this area, however, our latest inspections and the significant increase in reports suggest emissions management in this area of the landfill is no longer providing sufficient gas collection and improvements must be made.

Our position is clear: odour impacts at this level are not acceptable, and the operator must act quickly to resolve the issues.

We will carry out a thermal imaging survey of Lower Compton landfill using a drone to check for hotspots that may help indicate sources of odour.

We will carry out regular inspections of Lower Compton landfill as improvements are made to ensure they are effective.

We will provide a further update in April