Lower Compton landfill action plan

Odour mitigation plan – Lower Compton landfill

Hills is aware of a recent increase in complaints relating to odour in the Calne area. We take this matter very seriously, and where this is attributed to our landfill activities we would like to apologise. Our landfill site at Lower Compton is regulated by the Environment Agency (EA) – and we continue to co-operate fully and transparently with EA investigations, ensuring they have access to our site and operations.

We continually monitor and seek to improve operations at the Lower Compton landfill site to help contain fugitive emissions of landfill gas in accordance with our environmental permit. As a responsible business, we continue to work hard on implementing further improvements. Detailed below is a summary of the immediate, mid-term and long-term actions Hills Waste Solutions has agreed with the EA:

Immediate actions

Focus on improving short‑term containment.

• Following discussions with the Environment Agency, we ceased the use of trommel fines* as landfill cell cover material on 27 March.
• Additional plant has been mobilised to use soils across all areas of the operational cell (instead of trommel fines), to provide a minimum cover depth of 100 mm.
• Works to place soils as cover material commenced on 26 March and are expected to be completed within four weeks.
• Increasing the use of air-atomisers on the perimeter of the landfill cell. Air-atomisers disperse a fine water-based mist that interact with odour molecules to mitigate odour.
• We will also review EA drone flight data (once received) to identify any further targeted measures.

Mid-term actions

Bring forward engineered temporary and permanent capping supported by construction quality assurance (CQA).

• Contractor selection and mobilisation are underway to permanently cap areas of the operational cell at or near final waste levels.
• Capping is weather‑dependent because of the clay volumes required, but the anticipated start date is the first week of May 2026.
• Over the summer months we will look to permanently cap as much of the active cell as is practicable. This will be dependent on waste input volumes.
• Following permanent capping, we will install and connect permanent gas extraction infrastructure.

Long-term actions

Embed odour prevention into future cell design and waste acceptance controls.

• The design of future cells will be reviewed to allow for more frequent permanent capping.
• Trommel fines will not be used as cover material at Lower Compton.
• Gas extraction infrastructure (including horizontal and pin wells) will continue to be installed in future cells, as required to maintain effective operational gas control.

*Trommel fines are small particles of waste material, generally smaller than 40mm, that pass through a rotating cylindrical screen (trommel) during the mechanical sorting of construction, demolition, or mixed waste.