Prioritisation of Closed Landfill
Sites for Environmental Monitoring
The Scotland and Northern Ireland Forum for Environmental Research
(SNIFFER) seeks the development of an Environmental Monitoring
Prioritisation Tool in order to rank the potential risks to human
health and the environment from closed landfill sites in both Scotland
and Northern Ireland, until surrender of their Waste Management
The Scottish Environment Protection Agency (SEPA) and the Northern
Ireland Environment Agency (NIEA) therefore require a fair, transparent
and non-subjective system to prioritise closed landfill sites
in terms of risks to human health and the environment. This will enable
resources to be focussed on landfill sites where the greatest priority
is identified. The need for additional monitoring and/or remedial
measures can then be emphasised to the Operator. In addition, the tool
and subsequent ranking should assist both regulators and operators to
identify low priority landfill sites where licence surrender may be
This user manual is a clear and concise non-technical document that can
be used by a range of audiences including regulators and waste
management operators to accurately input data into the prioritisation
tool. The process flow diagrams and tool methodology, Appendices I and
II respectively, should be consulted in conjunction with this document.
Environmental Monitoring Prioritisation Tool
The purpose of the prioritisation tool is a first step in highlighting
potential risks from Closed Landfill Sites (hereafter referred to as
Sites) and identifying possible areas for further investigation
The initial task in the development of the environmental monitoring
prioritisation tool was a scoping exercise to assess the type and
quality of information available for sites in Scotland and Northern
Ireland. The desk based exercise reviewed the type of information
typically required for Site Closure Plans, Gas Risk Assessments,
Groundwater RiskAssessments and Pollution Hazards Assessments. The
selection process enabled a range of sites to be chosen that allowed
for differences in:
Once the initial data was collected this enabled the prioritisation
tool to be drafted using the information from categories above to feed
into a source-pathway-receptor layout. The tool follows the structure
as shown in the flow diagrams detailed within Appendix I. As shown in
Appendix I, the prioritisation tool clearly follows the established
criteria of source, pathway and receptor. The prioritisation tool also
incorporates a priority weighting system, which is used to rank the
landfill sites in order of priority, with particular attention given to
leachate and landfill gas migration issues.
- Waste types and quantities accepted;
- Hydrogeology; and
- Geographical/Geological setting.
Scoring and Ranking
The process flow diagrams contained within Appendix I illustrate the
scoring that is applied to each question or strand of a question. In
general the higher the score applied, the higher the priority and the
lower the score, the lower the priority. When the user answers
questions within the tool, the scores are collated and a priority level
is applied i.e. Priority 1, 2 or 3.
The priority spider diagrams shown in Appendix III illustrate how the
priority levels associated with gas, groundwater, surface water and
global warming is derived from the individual questions. Once the data
has been input to the prioritisation tool, the priority level
associated with gas, groundwater, surface water and global warming will
be produced. Table 1 illustrates the maximum priority score that can be
achieved for each parameter in the prioritisation tool.
Table 1 –
Maximum priority score
The priority levels from the closed landfill sites are identified as
Priority 1, Priority 2, Priority 3 or Negligible. The priority score
range for each of these options is split into quarterly intervals (e.g.
Gas Priority: negligible scores between 27 (lowest possible score
available) to 99, low scores between 100 to 171, medium scores between
172 to 243 and high scores between 244 and 315 (highest possible score
Note that where information is absent for key parameters, e.g. waste
type, then this in itself will create the priority level of the site.
This prioritisation tool is only for use on closed landfill sites with
existing Waste Management Licences.
In Scotland the following issues were the most frequently encountered
during the collection of landfill data:
In Northern Ireland the following issue was the most frequently
encountered during the collection of landfill data:
- For the majority of landfill sites there was limited
information on containment and abatement measures in place.
- The availability of monitoring data varied between sites,
including a lack of recent data, a lack of any monitoring data
or incomplete monitoring data sets.
- On a number of occasions it was also not possible to
identify where the groundwater monitoring points were located
in relation to the landfill sites (e.g. upgradient
- Other inconsistencies encountered included lack of
information on geological, hydrogeological and hydrological
It is also considered that it may be difficult for the user to identify
an appropriate answer in the prioritisation tool for the following
- For the majority of the sites the local hydrological regime
was not discussed with reference to the local river classification
(available under the NIEA General Quality Assessment scheme).
Given the above, there may be a significant number of sites that obtain
a high score due to the large number of unknowns that may be present
and the default option within the tool of applying the maximum score
where issues are not known or are uncertain.
- Basal lining of the landfill – the scale to which
the landfill is lined/not lined may not be apparent from the
information held on the public register.
- It may not be clear from the public register what surface
water, groundwater, landfill gas and/or leachate management measures
are in place.
- Geological and hydrogeological details may not be clear
from the public register.
The prioritisation tool assumes that the user has sufficient
information available to them to be able to answer all questions in the
tool. If this is not the case then the user will be required to make
assumptions to answer some questions. When assumptions are made these
should be noted in the comment box at the bottom of each page.
Copies of this report are available from the Foundation, in electronic
format on CDRom at £20.00+VAT or hard copy at
£15.00, less 20% to FWR members.
The report is available for download from the SNIFFER Website