16.4 Sites that have been used for the deposit of refuse or waste may generate explosive or otherwise harmful gasses. Thanet has approximately 26 such sites which are all listed in the National Landfill Atlas held by the Environment Agency.

16.5 A former landfill site will be unlikely to be actively gassing after 40-50 years of its closure. The Council is required to consult the Environment Agency, as Waste Regulation Authority, before granting consent for development within 250m of land which is, or has within 30 years of the relevant application, been used for the deposit of refuse or waste.

16.6 If an application for a new development/redevelopment or major change of use on or adjacent to a site included in the landfill atlas is received, then a full site-investigation report including gas monitoring will be required.

16.7 Where the presence of gas is discovered or it is suspected that it may be present during site development, the Council will require the applicant to arrange for an investigation to be carried out to determine its source and for satisfactory and effective remedial measures to prevent hazards from migrating gas (including accumulation into property or other confined spaces) during the course of development and during subsequent use of the site. Specialist design and construction advice will usually have to be sought by the developer in this regard.

16.8 For development on unstable land, it may be necessary for the developer to carry out specialist investigations and assessments to determine the stability of the site proposed for development and identify any remedial measures that will be needed to deal with instability. Areas known to the Council where land instability is likely to be an issue include:

• Minster Marshes
• Monkton Marshes
• Sarre Marshes
• Wade Marshes
• Land overlying Ramsgate and Margate caves
• Land overlying disused railway tunnel between Ramsgate main sands and the railway line at Broadstairs

Policy SE02 - Landfill Sites and Unstable Land

In considering planning applications on or near landfill sites, or where there is otherwise reason to suspect that potential danger from evolving or migrating gas may be present, or on land for which known or suspected instability might render it unsuitable for development, the local planning authority may require a specialist site investigation and assessment by the developer to identify any remedial measures required before determining such planning applications.

Development or redevelopment, including change of use, will only be permitted where:

1. The applicant/developer has demonstrated either that there is no unacceptable risk caused by the development or that appropriate remedial measures can overcome such risk;

2. The development would not adversely affect neighbouring land; and

3. Any necessary remedial measures can be achieved without unacceptable environmental impact.

Where the local planning authority is satisfied that the risks from landfill or ground instability can be overcome, planning consent may be granted subject to conditions or a legal agreement specifying the necessary measures to be carried out.