20-04-2013, 03:32 PM
LANDFILL SITE SELECTION
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INTRODUCTION
In terms of the Integrated Waste Management approach, progressive authorities are making
concerted efforts to reduce the amount of waste that goes to their landfills for final disposal.
Notwithstanding this, waste disposal by landfill remains the way in which almost all waste in
African and other developing counties is currently disposed. This is also the case in many
developed countries. Consequently, landfills and the provision of landfill airspace remain
essential elements in most waste management systems and strategies.
The Integrated Waste Management approach recognizes the above situation, so that the final
step in the hierarchy is waste disposal by landfill. Landfilling is thus endorsed, provided
appropriate standards are ensured to protect the environment, public health and quality of life.
THE GENERIC SITE SELECTION PROCESS
In almost any document on landfill site selection, the general objectives are to ensure that the site
to be developed is environmentally and socially acceptable, and thus sustainable. Specialist
consultants are often used for this purpose. These are technical, but often include environmental
consultants.
Early considerations in the technical process are the size (land area) and the strategic location
of the proposed site, to ensure that the facility meets the disposal need. While the size depends
on the waste stream over the predicted site life and provision for sufficient buffer zones, strategic
location is determined by the waste generation areas to be served and transport routes. It is
economically sound practice to establish the proposed facility as close to the generation areas as
possible, with a view to minimising transport costs. Often an “economic radius” is determined,
based on the existing or proposed mode of waste transport. This will define the initial area of
investigation.
Once the “economic radius” or “study area” has been identified, a Public Participation
Process (PPP) should be initiated and maintained throughout the site selection process. This may,
however, be controversial, as making the public aware too early can compromise the results. It
may stir up public and political resistance, i.e. the “not in my back yard” or NIMBY syndrome. It
might also lead to land speculation and soaring land prices, or losing a competitive edge in the
case of a private sector contractor. On the other hand, not to inform the public early on, or
presenting then with a fait accompli is guaranteed to generate mistrust and even more resistance.
Unless dictated by local regulations, therefore, informing the public is a case-specific issue.
THE GENERIC EIA PROCESS
Landfilling can have a significant adverse effect on the environment and quality of life of
adjacent communities, if not properly sited, developed, operated and closed. Consequently, all
these aspects should be addressed during the Environmental Impact Assessment (EIA), which
should take place during the landfill site selection process.
The EIA process includes not only the impact assessment, which involves specialist technical
issues, but also the associated Public Participation Process (PPP). In essence the PPP involves
liasing with the authorities, identifying the Interested and Affected Parties (IAPs), informing
them of the project and process and obtaining their input, which is taken into consideration by
addressing their issues and concerns. Where it occurs, justified public resistance to a proposed
landfill site should be regarded as a Fatal Flaw.
As noted, the initiation of the PPP is controversial and case-specific, but as a general rule, the
sooner the PPP is initiated the better, and it should be maintained throughout the landfill site
selection process. In practice, the actual EIA process will vary from case to case, but should
follow the basic principles of EIA, which are not addressed in detail in this paper.
SOME TECHNICAL ASPECTS OF LANDFILL SITE SELECTION
Negative mapping
Negative mapping is a preliminary tool used in the identification of Candidate Landfill sites. It is
used early in the study to eliminate the unsuitable areas in a study area and to identify “positive
window areas” for further investigation. This can be done on a small or large scale and makes
use of overlay technology to exclude the unsuitable areas. Such unsuitable areas are often
associated with the Fatal Flaws and unsuitable conditions, termed “exclusion criteria”. Some of
these appear below:
▪ Existing land use, development and population density (current and future).
▪ Unsuitable topography, drainage areas and areas of vulnerable to water pollution.
▪ Unsuitable geology (e.g. dolomites in South Africa) and soils.
▪ Existing and potential agricultural land use.
▪ Identified areas of environmental sensitivity (e.g. nature conservation areas).
Initially, manual overlays were used with a high degree of success. However, this methodology
was slow and tedious. Notwithstanding this, it remains the appropriate technology in developing
countries where normal and digitized maps are often scarce. In countries where digitized maps
are available, Geographical Information Systems (GIS), for which overlay technology is the
ideal application, is now the state of the art.
The due consideration of alternatives
Since the due consideration of alternatives is a fundamental principle in Integrated
Environmental Management (IEM) and the EIA process, and is also a fundamental principle in
landfill site selection. By presenting numerous alternatives and comparing them, the approach
goes a long way towards providing objectivity and a defensible approach.
One mistake that has frequently been made by the consultant (the author included) is that one
tends to view “alternatives” as Candidate Landfill sites. As soon as the IAPs become involved,
however, it soon becomes evident that (as indicated in the EIA section), “alternatives” also mean
other waste management solutions. These will include composting, recycling and possibly even
the latest “black box” technology that has been “sold” to the politicians. These issues have to be
addressed and the necessity of a new landfill confirmed, before the process can proceed.
Similarly, the IAPs may present alternative Candidate Landfill sites. While these are usually
intended to move the proposed landfill away from the area under consideration, they must be
taken seriously and considered on the same basis as the other Candidate Landfill sites.
In a landfill site selection exercise, generally the more alternatives identified, the better. In the
recent project to identify a new regional landfill site for the City of Cape Town, some 75
potential sites in total were considered. These were reduced to about 30 Candidate Landfill sites,
of which only 4 were short-listed and ranked. This example possibly represents an extreme case,
on account of it being a high profile project in an extremely sensitive environment.
[b]Ranking of short listed Candidate Landfill sites[/b]
Once Candidate Landfill sites have been identified, they must be evaluated to eliminate
unsuitable sites and to help determine the top ranking or short-listed sites. If there are a number
of sites, the “course screening” can usually be achieved by inspection and consensus, within an
objective team of experts, in a process similar to a Delphi method. Alternatively, a simple matrix
comprising the candidate sites on the one axis and selected criteria on the other may be used. The
criteria must then be appropriately weighted to reflect their relative importance. Scores are
assigned for each criterion for each site and added together to provide a site total. Thereafter,
sites are ranked from the lowest to the highest, and the latter are compiled into the short-list for
further consideration.
Once a short-list of the top ranking sites has been established, these must be compared with
one another in a “fine screening” exercise. For this process the above simple site-ranking matrix
may again be used. However, assigning numerical values is seen as very subjective, so at this
level variations may be used. One is a more detailed matrix based on an ABC system, where for
each criterion, the site rated best would receive an A, second best B and the worst, a C. This is
fine for three sites, but not for more sites or close ranking criteria. Another variant is to use
colours.
CONCLUSIONS
Based on the background and observations presented in the paper, the following general findings
are presented for consideration:
▪ Regardless of trends in some developed countries, landfills and landfill airspace remain
essential elements in waste management system in many countries, particularly in developing
countries.
▪ Proper landfill site selection process is fundamental to sound waste disposal practice.
▪ Because of IAP involvement, waste management consultants should make provision to defend
their work, in the event that it will be challenged - possibly in court. This will increase the
workload and lengthen the landfill site selection process. It also promotes the trend that more
detailed investigations are undertaken earlier in the process to ensure defensibility.
▪ Negative mapping is well served by the use of GIS. However, quality of input data, insight
into the science of landfill site selection and continual field validation are essential for good
results.