Lower Compton landfill - questions and answers

Our last update which included our action plan for the landfill at Lower Compton prompted several further enquiries from residents via Calne Town Council. We have collated and answered as many of those questions as possible below.

Health

1. Do these odours affect health, and will there be a health impact assessment?

The Environment Agency (EA) briefing dated 25 June 2025 which includes UKHSA (UK Health and Security Agency) feedback can be read here.

2. Is there a specific way we should be reporting our symptoms (other than just the smell) so that the health impact is officially recorded?

Any concerns about our operations can be reported to the Environment Agency or Wiltshire Council 

Gas collection 

3. What happens to gas collected from landfill?

All gas collected through the collection network on site is diverted to a power generation plant on site, converted to electricity and exported to the national grid. There are three on-site engines producing enough electricity to power approximately 2,500 homes.

Waste types

4. What are ‘fines’ and why have they caused such a sudden increase in smell?

The site’s environmental permit allows for the landfill input of trommel fines which are small parts of waste which have passed through a rotating screen (trommel) as part of waste processing. While the composition of trommel fines depends on the material being accepted at the processing site, they are typically a mixture of organic and inorganic waste types including soil, sand, plastics, wood, and aggregates predominantly from the construction and demolition industry. This waste type can contain a level of sulphate from sources like plasterboard, which under certain conditions can produce hydrogen sulphide, which is odorous and commonly found in landfill gas.

Soil coverage to reduce odours in active cells

5. How long will it take for the new soil layers to properly "seal in" the smells from the older layers?

The use of soil as cover of waste is a standard procedure in a working waste cell to help manage landfill waste including to alleviate odours. The initial placement of soils across the operational cell is programmed for completion by 20 April 2026. Sealing requires permanent capping (see below).

6. Is 100mm soil cover considered a “gold standard” for stopping smells? Will Hills commit to adding more if the 100mm doesn’t fix the problem?

Once the initial 100mm of soils has been placed we will monitor its effectiveness and continually review the need to place more soil cover if required ahead of clay capping.

Clay capping of completed cells

7. What weather conditions are needed for capping?

As clay is used to cap completed cells, it cannot be placed during very wet weather, so engineering works are programmed for the drier summer months.

8. Is there a plan B if weather conditions prevent immediate capping?

The contract to complete the capping works is expected to take 13 weeks. We have programmed the works early in the summer to allow for any delays due to the weather.

9. How much capping is ‘practicable’?

We can only place the final cap on areas of the site which have been filled to the ‘final waste’ levels. By ‘practicable’ we mean we will cap all areas of the site which are at final waste level at the time when the capping works are being undertaken. The area of capping is therefore dependant on the waste inputs into the site which can be very variable. The capping of landfill cells is determined by the required landscape contouring profile of the land as required by the site’s planning permission.

10. When will permanent capping be achieved?

We will cap as much of the operational cell as possible over the summer months, but this is dependent on several external factors such as weather and waste inputs.

11. What is the difference between 'operational' cell and 'active' cell?

There is no difference, they both refer to open cells which are currently accepting waste inputs.

Other questions

12. What do air-atomisers do? Are they just fragrance and are they safe for people with asthma, pets, and local wildlife?

Approved air atomisers are safe and used widely across the industry and are an odour masking agent and dust suppressant used only on site.

13. Can drone data and the air monitoring results be shared with the public in a simple, easy-to-read format so we can see the progress for ourselves?

This data is collected by the EA and not by Hills.

14. Would Hills consider a simple "Progress Tracker" on their website?

Regular updates on the action plan will be given via the liaison committee and on the website. Please note that liaison committees are not public meetings - they are attended by County, Town and Parish councillors along with representatives of Wiltshire Council and the EA.