Landfill gas

Guidance on new development on or near landfill sites

What is landfill gas?
Landfill gas is an end-product of the degredation of biodegradable waste in a landfill site.  It is a mixture of methane and carbon dioxide, plus trace concentrations of a range of organic gases and vapours.  Methane is flammable in air; without proper management the migration of gas from a landfill can give rise to the risk of fire and explosion in nearby buildings, underground services or voids.  It also presents a risk from asphyxiation.

The uncontrolled emission of landfill gas from such sites is clearly undesirable and the technology for controlling its migration and venting is now well developed.

There are simple constructional techniques which can be adopted to ensure that emissions are properly channelled and vented, both during and after the construction period.

Planning background
Growing concern about the potential hazards of gas generated from landfill sites resulted in advice from government in the form of Circular 17/89.

The Town & Country Planning (General Development Procedure) Order 1995, requires the local planning authority to consult the Environment Agency before granting planning permission for development within 250m of land which is, or has been (in the 30 years before the relevant application) used for the deposit of refuse or waste and which has been notified to the local planning authority by the Environment Agency.

Where are the Gravesham sites?
In September 1990, Kent County Council published the Kent Landfill Atlas for Gravesham.  The Atlas identifies those sites in the Borough which are known to have been used at some time for the disposal of waste.  A database accompanying the Atlas gives details of each of the sites with regard to site history, local geology and the surrounding environment.

The database also identifies whether there is a requirement for consultation under the General Development Procedure Order, should a planning application be received by the local planning authority for development on, or adjacent to these site locations.  Sites closed before 1940 are unlikely to pose a hazard although potentially there may be a problem in relation to other contaminants.

Part of the new contaminated land regime introduced in April 2000 under the Environmental Protection Act 1990 Part IIA, requires local authorities to identify the nature, extent and distribution of contaminated land which will include sites used for landfill.

This information will be kept on a register available to the public and will be amended as and when new information becomes available.

Planning requirements
In response to consultation with the Environment Agency the local planning authority may be asked to request the applicant to submit a full site investigation report, including gas monitoring, to accompany the application.  A list of consultants who could provide advice and expertise to further investigate any site is available for inspection at the Planning and Regeneration Services offices.

Landfill gas migration is a material consideration.  This means planning conditions could be imposed to manage the emission of gas from a landfill site, or to ensure suitable precautions are taken with construction methods.  Permission can be refused if reliable arrangements cannot be made.

The cost of monitoring and taking precautions to minimise the effect of gases from landfill sites is solely the responsibility of the developer.

Building control requirements
The construction of new buildings, or extensions to existing buildings, requires consent pursuant to Building Regulations, 1991.

The principal design objectives are to construct a gas-proof barrier across the whole site of the building and to disperse any gas safely.

The walls, floors and foundations of the building should be constructed so that gas is prevented from entering occupied areas or accumulating in voids.  A preferential escape-route for gases away from the building is provided to enclosed voids within, or under, the building.  Special attention also needs to be taken into account in the design of service pipes and their effect in penetrating the floor slab.

The protective measures can only be assessed once the results of a site investigation have been obtained.

Landfill gas sites in Gravesham

• Asda site, IBE
• Botany Marshes
• British Uralite, Higham
• Broadness Marshes
• Campbell Road Pit
• Canal Road, Higham
• Canal Road, Gravesend
• Comma Oil, Denton
• Dyke's Pit
• Filborough Farm
• Holyoake Mount
• Lennox Road Pit
• Lewis Road, Istead Rise
• Lodge Pit, Cobham
• Nine Elms Grove
• Norfolk Road
• Northfleet Power Station
• Pine Avenue
• Shamrock Road
• Springhead
• Springhead Road
• Former Tollgate Stables
• Westcourt