Contaminated Land &
Water Working Group
Landfill Sites
A landfill is an area of land where people have disposed of waste
material. People have been landfilling waste in local tips for thousands
of years, but it is generally only in the last century that large scale
landfilling has had the potential to significantly impact on the
environment.
The proximity of a landfill to a property or site has implications for
developers who will need to ensure that any new development is adequately
protected from landfill gas. Information on landfilling activities is
therefore one of the main components of an environmental search.
A brief history of waste regulation in the UK
Waste disposal regulation in the UK began with the introduction of the
1848 Public Health Act. The Act made provision for waste to be stored in 'midden
heaps' located next to people's houses. 'Midden heaps' were large holes in
the ground into which rubbish and sewage was thrown. When the pits were
full, they were dug out and the waste taken away by horse and cart.
The major change in waste collection came soon after in the publication
of the 1875 Public Health Act. The Act was introduced as a direct result
of a cholera outbreak in London, which had claimed many lives. The main
focus of the 1875 Act was to charge Local Authorities with the
responsibility for removing and disposing of waste.
The introduction of The Clean Air Act in 1956 placed new restrictions
on the burning of waste. This led to a change in the composition of the
material disposed of in landfill sites as previously most domestic waste
was burnt prior to disposal as ash.
In 1974 the Control of Pollution Act meant that all landfill sites had
to be licensed and for the first time, details of the type and volume of
waste was recorded.
Since 1994, waste disposal has been tightly regulated by Waste
Management Regulations. Modern landfill sites are regulated by the
Environment Agency and are highly engineered structures, designed to
contain and manage the waste and waste products. They can also be used to
generate electricity from landfill gas.
Today, the UK National Waste Strategy is promoting a more sustainable
way in which we manage our wastes. European Union and UK Government
targets have been set which aim by 2020, to reduce the amount of
biodegradable municipal waste which it landfills to 35 percent of that
produced in 1995. This will be achieved by a combination of, recycling,
reducing packaging, composting and re-using materials.
What are the main risks associated with landfills?
Each landfill is different and can vary in age, type and volume of
waste filled, proximity to receptors and how well it has been engineered.
However the main risks associated with landfilling are common to all
landfills and can be classified as either pollution of surface waters and
groundwater by leachate from the filled material or health effects and
explosive risks from landfill gas.
Leachate forms within a landfill when waters circulating through the
waste pick up different contaminants. In older landfills where leachate is
not contained it may migrate from the landfill and cause pollution of the
ground water or surface waters.
Landfill gas is a breakdown product from the putriscible component of
domestic waste e.g. food, garden waste, wood and paper. The principal
reaction occurs when bacteria break down the organic matter into methane
and carbon dioxide. The potential for a site to produce gas is dependent
upon the age of the site and the nature of the fill. The potential for gas
to migrate from the landfill depends on whether the site has been properly
engineered in order to manage the gas which is produced.
There are many hundreds of trace gases that can also be produced from a
landfill site, but following normal atmospheric dilution most do not
usually represent a health hazard. The more common trace gases include
hydrogen sulphide and carbon monoxide.
What can be done to reduce the risks from landfills?
Leachate can be pumped and treated before it leaves a landfill and
should therefore not cause any further problems. This typically occurs in
older landfills where no containment systems have been put in place.
Landfill gas may give rise to a variety of hazards if it migrates to,
and accumulates in, a property or confined space. If generated in
sufficient quantities, methane gas may form an explosive mixture with air
(at approximately 5-15% by volume). It can also act as an asphyxiant and
in particular circumstances may be toxic. Carbon dioxide is an
asphyxiating gas which can cause adverse health effects even at relatively
low concentrations.
In modern landfills the installation of gas management systems such as
venting or extraction measures will significantly reduce the risk of gas
migration to neighbouring properties.
The incorporation of protective measures such as a sub-floor void and
gas resistant membranes within neighbouring buildings will also reduce
potential risks associated with landfill gas. The need to incorporate such
measures into new developments is addressed through the planning
procedure.
What is being done about old landfills that have no containment
measures?
Detailed information for sites which were completed prior to the 1974
regulations is often scarce. Your Local Authority will be examining old or
closed landfills in their area as part of their Contaminated Land
Inspection Strategy and will be addressing any risks in due course under
Part IIA.
What are closed landfills used for?
Most closed landfills are returned to public open space or used for the
grazing of livestock. Some of the older inert landfills, which pose little
risk and are being developed for commercial and industrial use.
Further Information
For specific details of landfill sites within your areas you should
contact your own Local Authority.
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