Information and Advisory Note Number 39 Back to menu
1 1 This Information and Advisory Note forms part of the 'Rivers and their
catchments' series and should be read in association with 'Rivers and their
catchments: an overview' (Information and Advisory Note No 18) and Policy
Guidance Note 94/5- 'Waste Management'.
1.2 This Note reviews the impacts of landfill activities on the aquatic
environment. This includes not only the physical and chemical impacts upon
rivers, but also their knock-on impacts upon aquatic biota Current mitigation
and restoration techniques are reviewed and some of the relevant major
legislation is outlined.
1.3 Landfill practice is the disposal of solid waste by the infilling of voids on
land. The voids may be natural, such as valleys, or man-made, such as quarries
or other mineral excavations The composition of any one landfill site is highly
variable, even when the site licence specifies a particular class of waste. The
difficult constituents in a landfill are the vegetable and putrescible elements,
which in most cases contribute to the generation of leachate and methane.
1.4 Water enters a landfill from a number of sources, for example from
precipitation, groundwater, surface run-off, and the disposal of liquids or
sludges. The amount of water entering a landfill depends upon many factors, such
as the seasonal distribution of the water balance, the geology and hydrogeology
of the site and the soil type and vegetation cover of the original and the
completed site and the surrounding area. Water provides three major
functions in landfilling: as a medium essential for bacterial activity in
organic waste and for chemical breakdown, as a medium for movement of
contaminants, and as a medium providing dilution.
1.5 Landfilling activity is a major issue which needs to be addressed as part of
an Integrated Catchment Management (ICM) approach (See Note No. 18). ICM can be
regarded as comprising catchment management plans to which all the major
interests in the catchment subscribe To be effective, such plans must be
consistent with local authority development plans and asset management plans of
water supply utilities, and vice versa.
2.1 Landfill activities have the potential to alter the quantity and quality of
groundwater and alter surface water in the locality. The significance of the
potential impacts will vary according to the phase of operation, the scale of
the operations and the sensitivity of the local water resources.
2.2 Potential impacts on surface waters.
2 2.1 The construction phase has following potential impacts:
2 2.2 The operation phase has the additional potential to affect surface run-off volume and quality by
2.2.3 The restoration/closure phase can affect run-off and water quality by:
2 3 Potential impacts on groundwater
2 3.1 During the construction phase the following may affect groundwater level
and/or quality
2 3.2 The operation phase may have the following major impacts on groundwater
2 3 3 The restoration phase has two potential impacts on groundwater level and quality.
2 4 Leachate Generation and Quality
2 4.1 Leachate is produced when water or
another liquid comes into contact with waste,
particularly household waste, in a landfill As
water percolates through, it leaches material
from the waste Soluble inorganic
components are dissolved and organic wastes such as paper, cardboard and
foodstuffs degrade by microbial action to simpler compounds which are soluble. As
water percolates through the landfill it generally deteriorates in quality,
resulting in a polluted liquid which vanes in colour from light brown to black,
and smells sweetish and sickly. Its polluting potential may be 10 to 100 times
that of raw sewage.
2 4.2 The main components of leachate are
2 4 3 Leachate quality and strength is affected by
Leachate quality is primarily dependent upon the balance between acetogenic and
methanogenic phases of degradation. Acetogenic leachate is produced during the
early stages of landfill and is of high organic strength Methanogenic leachate
occurs during later phases of landfill when organic compounds are actively
converted to landfill gases, leaving a residue of humic-type material Table 1
shows typical qualities of domestic waste leachates in the UK
3 1 The major potential sources of ecological impact from landfill activities are.
3.2 The construction phase has the potential to have the most direct impact in
terms of physical loss and disturbance, while the operation and restoration
phases tend to expose plants and animals to contaminants.
3 3 Site drainage alteration may result in habitat loss not only within the site
but also in the surrounding area Habitat diversity may also be affected by
changes in salinity and chemical composition of groundwater in and around the
site.
3.4 As discussed in Section 2 3, leachate composition is variable However, the
following effects on the aquatic biota are indicative of landfill leachate.
3.4.1 Major ions, as listed in Section 2.4 2, may have varying toxicities
depending on the target organism. For example, chloride ions can influence the
osmotic balance in some fish species; Atlantic salmon parr suffer high
mortality in water with chloride concentrations over 22%.
3 4.2 Flora and fauna respond in varying ways to trace metals. For example, algae
such as Palmella, Oedogonium and Pallmellococcus are moderately sensitive to
chromium, while rainbow trout (Salmo gairdneri) are tolerant to nickel, though
it can affect their gill morphology.
3 4.3 Reduction in dissolved oxygen levels and increases in concentrations of
hazardous organic compounds (such as phenol) cause a change in biological
community composition and abundance. For example, salmonids are sensitive to low
dissolved oxygen levels, and phenol causes internal haemorrhaging and
inflammation of gills in rainbow trout. Pesticides and herbicides leached from
landfill sites may affect wildlife; Algistat was found to kill Spirogyra at 0 8
parts per million (ppm) and be toxic to fish at 0 7 ppm.
3 4 4 The impacts of suspended sediment on in-stream biota are covered in
Information and Advisory Note No 23 - 'Rivers and their catchments, river
dredging operations'. Sediment from disturbed areas, paved areas, site vehicles
and stockpiled soil may cause substrate siltation, increased suspended sediment
and turbidity, all of which affect the composition and abundance of in-stream
communities.
3 4.5 Release of oil, hydraulic fluid and
stored chemicals has the potential to affect
surface water and groundwater and organisms
which live or rely upon such waters, both at
the site and for some distance downstream.
4 1 Construction phase
Construction impacts will be best mitigated by good site practice Site drainage
control measures will help to reduce the impacts of polluted site run-off and
the changed run-off characteristics of the site. The objectives should be to
minimise the area and time of exposure of bare soils and unvegetated areas, to
provide facilities for the removal of pollutant loadings from any drainage from
the site, and to provide for adequate containment or retention of any spillages
or accidental discharges. This should include collection of vehicle washing
effluents, routing of all-site drainage to settlement lagoons and the use of
impervious surfaces beneath storage tanks
with bunding to provide for 110% of the capacity of the tank.
4 2 Operation phase
Operational mitigation measures should be based on two objectives first, to
ensure that run-off from the site does not exceed existing run-off from the
undeveloped site, and second, to contain and control contaminated water and
liquids generated on the site. Usually, total containment of the site is likely
to be required. Protection of groundwater from spillages and fuel leaks from
vehicles or storage tanks can be achieved by use of low permeability surfaces,
engineered drainage systems, bunding of tanks and storage areas, and routing of
all surface run-off and water derived from operations to a treatment facility
such as a series of settlement lagoons (see Information and Advisory Note No 54
-'Rivers and their catchments impacts of opencast coal mining on water quality')
4.3 Restoration phase
Restoration of landfill sites should provide for collection and channelling of
rainfall by use of surface drainage and piped sub-soil under-drainage in the
landfill cap to perimeter drams or soakaways. In addition, provision of control
for storm event run-off must be made. Restored slopes should be of sufficient
gradient to prevent ponding, but not so steep as to encourage erosion Gradients
of around 1 in 30 are recommended, though slopes of 1 in 10 or 1 in 20 may be
more effective Regular site monitoring of both groundwater and surface water
should also be undertaken to allow detection of leakage from the landfill.
Diverted watercourses may be either restored to their former courses, if
practicable, or maintained in their new courses with creation of natural channel
characteristics.
4 4 Leachate management
Proper management of leachate is essential in
any landfill operation, given the potential for
large quantities of contaminated liquid to
pollute adjacent groundwater and surface
water The key components of a leachate management scheme are:
5.1 Kinneil Kerse landfill site, Falkirk
5.1.1 Figures 1 and 2 show tipping and infilling of land adjacent to the Kinneil
Kerse SSSI, immediately south of the River Forth, between Grangemouth and
Bo'ness. The photographs show landfill wastes lying in and adjacent to a wetland
feature associated with the tidal influence of the River Forth by the western
boundary of the site.
512 Careful management of the site is required to mitigate potential adverse
impacts on local watercourses and waterbodies relating to leachate and refuse
from landfill operations.
6.1 This section outlines some of the important legislation relating to landfill
activities and the aquatic environment.
6.2 Under the Environmental Protection Act 1990, a Waste Disposal Authority has a
duty to produce a Waste Disposal Plan which
should be based upon an investigation into the requirements for the disposal of
waste in an environmentally acceptable way. In addition,
Section 34 of the Act states ' it shall be
the duty of any person who imports, produces, carries, keeps, treats or disposes
of directive wastes, or, as a broker has the control of such waste to take all
measures applicable to him
in that capacity as are reasonable '. This
means a waste holder must identify the type of waste, the problems associated
with the waste and whether or not it requires special disposal facilities.
The European Union Directive 85/337/EEC on the effects of certain public and
private projects on the environment is implemented in Scotland by the
Environmental Assessment (Scotland) Regulations 1988, SI No 1221 Landfilling
falls under Schedule 2 of these regulations, an environmental assessment is not
mandatory, but is required if a project is likely to give rise to significant
environmental impacts. The Department of the Environment issues an advisory
booklet, "Environmental Assessment a Guide to Procedures", which is intended to
assist both Unitary Authorities and developers in their interpretation and
application of the statutory requirements.
6.3 From 1 April 1996, the Scottish Environment Protection Agency combined the
existing pollution control functions of the River Purification Authorities, Her
Majesty's Industrial Pollution Inspectorate and local authorities. It has a
statutory conservation duty but its freshwater work does not extend beyond that
carried out by the River Purification Authorities.
6 4 Under the Control of Pollution Act 1974, as amended by Section 23 of the
Water Act 1989 and Section 21 of the Environment Act 1995, SEPA has statutory
responsibility of forestalling or remedying the pollution of water. The Acts
also enable consents to discharge to be granted and imposition of penalties for
contravention In practice, consents are the main form of controlling pollution,
though SEPA also advises operators on procedures and treatment measures.
6 5 The Dangerous Substances Directive 76/464/EEC, on pollution caused by
certain dangerous substances discharged into the aquatic environment, is a
framework directive which sets out general principles of control Various
daughter directives under this framework set out emission limits, quality
objectives and reference methods for
measurement and monitoring procedures for particular harmful substances.
Scottish Natural Heritage 1994 Waste Management Policy Guidance Note 94/5
6.6 The protection of groundwater is dealt with by the Groundwater Directive
80/68/EEC on the protection of groundwater against pollution caused by certain
dangerous substances.
6 7 There are various other directives which specify standards for water for
various uses, or for the support of various types of aquatic life. Their
requirements are transposed in UK law via Regulations. For example:
Department of the Environment 1986 Landfilling Waste- a Technical Memorandum for
the Disposal on Landfill Sites Waste Management Paper, No. 26 London, HMSO.
Department of the Environment 1989 Environmental Assessment, a Guide to
Procedures London, HMSO
Department of the Environment 1995. Landfill Design, Construction and
Operational Practice Waste Management Paper, No. 26B London, HMSO.
Hellawell, J.M. 1986. Biological Indicators of Freshwater Pollution and
Environmental Management London, Elsevier Applied Science Publishers
Petts, J and Aduljee, G. 1994 Environmental Impact Assessment for Waste
Treatment and Disposal Facilities Chichester, John Wiley
Scottish Hydrological Group 1988. Hydrology of Landfill Sites. Proceedings of
Scottish Hydrological Group / British Hydrological Society Symposium Glasgow,
November 1988.
Acetogenesis - conversion by bacteria of soluble acids to acetate, carbon
dioxide and methane, and of carbohydrates, hydrogen and carbon dioxide to acetic
acid
Aerobic - in the presence of oxygen
Anaerobic - in the absence of oxygen
Ammoniacal Nitrogen - a measure of the nitrogen compounds present (generally
from biological activity) by their conversion to ammonia (NH3) A few mg L-1 may
indicate pollution.
Biochemical Oxygen Demand (BOD) - the amount of matter present in water that can
be readily oxidised by micro-organisms. It is a measure of the power of this
material to take up oxygen in the water which would otherwise be available to
biota
Bund - embankment of clay or other
impermeable material used to limit the lateral movement of water and waste.
Capping - the covering of landfill which is normally impermeable, to prevent the
ingress and egress of water
Chemical Oxygen Demand (COD) - a measure of the amount of chemically oxidisable
matter present in a liquid
Doming - practice of raising the centre of the capped area to encourage surface
run-off
Impermeable - describes a material, natural or synthetic, which does not allow
the passage of water through it.
Infiltration - seepage of water into the soil or waste from the surface
Lagoon - settlement pond for material deposited from solution or suspension
Leachate - liquid which seeps through a
landfill. Substances are
dissolved or washed out by the liquid as it percolates through the waste.
Liner - a natural synthetic membrane
used to line the base and sides of landfill excavations to prevent escape of
leachate.
Methanogenesis - methane-generating bacteria (methanogens) metabolise acetate
and formate produced during acetogenesis, to generate methane and carbon
dioxide.
Percolation - flow of liquid under gravity through a material.
Putrescible - describes a material which is readily decomposed by bacteria
Spoil - material removed during
excavation for mining or landfill purposes. Usually mounded at the site
periphery during site operations and used at a later date for site restoration.
Suspended Solids - solids which
are suspended in a liquid.
Total Organic Carbon (TOC) - a measure of the amount of carbon present in the
'organic chemical' fraction of a material
Scottish Natural Heritage
Research and Advisory Services Directorate
2 Anderson Place
EDINBURGH
EH6 5NP
Tel: 0131-447 4784
Earth Sciences Branch {provide information on physical processes in the aquatic
environment),
Aquatic Environments Branch (provide information on biota in the aquatic
environment)
Scottish Natural Heritage
Policy Directorate
12 Hope Terrace
EDINBURGH
EH9 2AS
(provide information on policy, strategy and
legislation issues)
Tel: .0131-447 4784
Jonathan Clark
Earth Sciences Branch
Scottish Natural Heritage, Edinburgh