In the Appraisal of Sustainability (AoS) that accompanies the proposed Airports National Policy Statement (NPS), the Government has undertaken a high level assessment of the effect on the water environment of the Heathrow Northwest Runway scheme. The proposed Airports NPS sets out the requirements in relation to water quality and resources which any applicant for a Development Consent Order would need to meet. This potentially includes the effects on water bodies or protected areas under the Water Framework Directive. The Government has not estimated the time it will take to decontaminate land. This a matter that would need to be addressed as part of any application for development consent. The AoS identifies a range of sources and pathways for contamination within the site boundary. These include two active landfills, 16 historic landfills and 11 registered pollution incidents, five of which are classified as significant.