There are many factors to be considered when selecting a site for a sanitary landfill. It is a process which requires a systematic and scientific approach. Here, we look at the principles and problems involved.
by Hansjörg Oeltzschner
Starting out: principles and preconditions
In the planning of a sanitary solid waste disposal facility some basic factors must first be established, and the following questions have to be answered:
- What kind of waste is supposed to go to the landfill?
- What amount of waste will have to be disposed of in the landfill?
- For how long a period must the site be available?
- As a consequence: what must be the minimum size of the planned landfill?
- What economical criteria must be taken into account?
- What traffic conditions are necessary for the transport of waste to the site?
- How are the existing traffic links?
- What kind of excluding or restricting factors have to be respected in the process of site identification and evaluation?
The identification and final selection of a landfill site should be carried out in four main steps (see Table 1). This will focus the process.
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Identification and selection of a site – scheme of work
These phases must be adhered to when planning suitable sites:
Phase one: Data collection and exclusion of unsuitable areas ("negative mapping")
For a general survey (desk study), data and information are collected on each area proposed for the planning of a new sanitary landfill. At first the relevant municipalities and/or regional authorities, pertinent institutions, national geological services etc. have to be contacted and interviewed in meetings.
For phase one it is necessary to study these factors: topography/morphology, geology/geo-hydrology/ hydrology, seismic conditions, pedologic, climatic/meteorological conditions, geotechnical situation, surface water bodies, land-use, nature protection (national parks, forests, nature monuments etc.), cultural sites (religious, heritage etc.), military areas, distance to settlements (existing and planned) and distance to airports (existing and planned).
Some of the criteria excluding an area from the site selection process from the beginning include: existing or planned (i.e. already officially registered) drinking water protection and catchment areas, high-flood areas, areas with unstable ground like swamps, moors and/or marshes, areas with an extreme morphology (steep slopes, danger of landslides/avalanches etc.) and protected areas.
According to the "Ford Act",2 areas nearer than 6 miles (9.66 km) to an airport must be avoided. The local situation, in particular flight and landing routes, bird population, and special legal regulations have to be checked.
By a general check of these criteria a desk study can be created, and areas which are obviously unsuitable can be eliminated in the early stages. Using the information, a "negative map" will show all the areas, which may not be suitable for the construction of a sanitary landfill.
Phase two: Identification of possibly suitable areas ("positive mapping")
Areas of interest which pass phase one successfully are investigated with respect to:
- availability of land
- minimum size and geometry of site
- traffic links
- access to selected sites
- investment budget
- acceptability by the public.
Areas that pass these tests are regarded as potential sites. They are mapped as "positive" areas using a colour-code system on a map.
Phase three: On-site-investigation
Phase three comprises visits of the areas defined "positive" with onsite investigations of the geologic, hydro-geologic and geo-technical situation at the potential sites. For this important stage of the site selection process, a rather simple but very efficient method of collecting and presenting the relevant data has been developed. It is the use of checklists which help to evaluate the investigated site.
Three types of checklists or evaluation lists are used which can be used for landfill sites as well as for the evaluation of waste transfer stations and composting plants. These checklists are a useful tool for the detailed technical and ecological evaluation of sites. They can be used during field reconnaissance and may also help to make the site evaluation process more comprehensive to third parties, who even can use the lists themselves and get a much better understanding of the decision process. The site-evaluation check list focuses on six main groups of data and parameters:
- general data, e.g. volume, traffic links, distances from main waste sources, morphological situation
- hydrogeology and water management
- geotechnical and constructional aspects
- meteorological aspects
- aspects of emissions
- nature protection and land-use.
At the end of the field visit the investigator should be able to decide, whether further research on the site should be done, or if the site seems unsuitable. Another option could be to postpone more detailed investigations at this site until results of alternative sites are available, which might indicate that no better site could be found.
In many cases it is a combination of various negative factors which leads to the exclusion of a site from further investigation. In some cases, an area may eventually have to be rated as "less suitable" or "not suitable", because of just a few, but very important (decisive) negative factors, e. g. hydrological risks, no competent geological barrier, etc.
If no suitable site is found, the applied set of criteria/additional criteria should be reconsidered. An alternative site might simply require additional technical measures to mitigate the undesirable aspect of the site.
Environmental impact assessment
Even if designed, constructed and operated according to state-of-the-art systems a sanitary landfill will have an impact on the environment at the site location. Therefore, an evaluation of the ecological/environmental impact has to be integrated into the evaluation of a proposed site. Early in the project, this can be done using a simple method based on the results of the field visits. If the site is located in a very sensitive area a detailed investigation of the proposed area has to be carried out. A good general help is the World Bank"s Operational Manual BP/OP 4.017 concerning environmental impact assessment.
For a general evaluation of the environmental impact it is sufficient to use only the environmentally most important criteria, such as:
- neighbourhood/settlements (concerning possible problems of noise, odour, "airborne" waste, local meteorological situation, )
- forests/parks
- wildlife/biotopes/vegetation
- surface water quality (impacts on existing water bodies)
- groundwater quality (leachate)
- air quality (methane gas, bad odours)
- soil quality
- agriculture / farming
- traffic conditions (access to the site)
- aesthetic aspects/impacts on the local ecological situation.
It is necessary to check the range of the environmental impact e.g., if after the closure of the site there will be a short-term or a long-term influence; if the influence is only local, or wide-ranging; reversible, or irreversible; if it will be significant or negligible. The degree of the environmental impact should be evaluated as: very high, high or minor. Positive results also have to be addressed in the EIA.
 At the Kabul site onsite ground exploration was vital in determining suitability |
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Overview of on-site ground exploration
After having executed a comparative evaluation of pre-selected sites, a certain number of sites (normally only one or two) may be rated favourably for further investigations. At such locations special investigations have to be carried out on-site. To explore the ground of a site it is recommended to use "indirect" and "direct" methods.
Indirect methods are geophysical techniques, like geo-electrical survey methods, ground-penetrating radar and seismic refraction. The selection of the proper geophysical techniques depends on the geological setting. The application of these methods does not require drilling or excavation. However, the geophysical investigations should always be combined with direct methods of exploration. While geophysical procedures can provide large amounts of data at a relatively low cost, they require careful interpretation by qualified experts. Therefore, geophysical data must be verified by results from direct exploratory procedures such as borings or test pits.
 Geological conditions in Kabul were monitored, and samples analysed |
Direct investigation methods include the excavation of pits and trenches, the drilling of boreholes and monitoring wells. Direct methods allow observation of the geological conditions on the site to take samples and to obtain direct measurements. Boring logs provide descriptions of the soil strata and rock formations, discontinuities (rock joints, faults, ancient slip surfaces) encountered, as well as the depth at which they occur. In addition, boring logs should provide standard penetration test results and rock quality designation for runs in rock. The boring logs should record the intervals for, and the results of any field hydraulic conductivity testing conducted in the boring. Direct methods allow the investigator to obtain samples of subsurface material for laboratory testing of its engineering properties. Laboratory data should be set out in summary tables.
It is particularly important that the investigation boreholes, test pits and trenches, and other procedures, be performed as near as possible to the site, if not within the boundaries.
Phase four: Final proposal and final decision
After comparison of the results of the site investigations at the areas of interest, one site will turn out to be most favourable. The properties of this site will be presented in a report with the recommendation to select this site from the candidates which were examined and compared. Furthermore, an evaluation of costs and of cost benefit ratio is necessary (and may lead to the exclusion of the site).
The described methodology has been applied successfully in many countries during the last decade e.g., Afghanistan (Kabul), Algeria (several provinces), Benin (Cotonou), Botswana, Egypt (Province of Aswan), Gaza-Strip, Grenada, P.R.China (Beijing), Indonesia (Bogor and Bandung), Mauretania (Nouakchott), Montserrat, Montenegro (Tivat), Nepal (Kathmandu, Phokhara), Thailand (Chiang Mai, Phitsanulok), Tansania (Dar Es Salam), Tonga (Vava"u), St. Lucia.
Prof. Hansjörg Oeltzschner is a senior expert on environmental assessment and waste management and head of department for environmental geology and geotechniques at the Bavarian Geological Service.
e-mail: prof.oeltzschner@T-Online.de
For the full-length version of this paper including copies of the checklists used in the site selection process, please visit www.geowiss.uni-hamburg.de/i-boden/landfill-technology/fundamentals/TCLT_Fd_02.01_200906.pdf
This article is on-line. Please visit www.waste-management-world.com
References
- Aust, H. et al., 1997: Geowissenschaftliche Rahmenkriterien zur Standorterkundung für Deponien.- Geologisches Jahrbuch, Reihe G, E. Schweizerbarth"sche Verlagsbuchhandlung, Stuttgart
- EPA, 2003: Federal Register Environmental Documents: Municipal Solid Waste Landfill Location Restrictions for Airport Safety
- EPA, 2003: Location Criteria Standards
- Gauff Icon, IBU, 2005: Environmental Report, Part I: Solid Waste (Emergency Infra¬structure Reconstruction Project (EIRP), Sanitation Improvements in Kabul City),
- Oeltzschner, H.; MUTZ, D.,1996: Guidelines for an Appropriate Management of Sanitary Landfill Sites (2nd ed.), ed. by Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), Eschborn
- Oeltzschner, H., 2000: Special Aspects of Identification, Construction & Operation of Sanitary Landfills under Tropical Conditions.-ISWA-Hongkong 2000; International Symposium & Exhibition on Waste Management in Asian Countries. Hong Kong
- World Bank, 2004: The World Banks Operational Manual "Environmental Assessment" Operational Policies BP/OP 4.01, USA
Case study: Kabul, Afghanistan (2004?2007)
A recent landfill site selection and evaluation (for Kabul municipality) is demonstrated here as a case study.
 Map of the city of Kabul showing existing dumpsites and potential sites for a sanitary landfill |
The investigations had been part of an overall assessment of sanitation improvement in Kabul, a project of World Bank carried out by Gauff Engineers, Frankfurt and ICON-Institute Cologne. One task of the experts had been the:
- Technical and environmental evaluation of the existing dumpsites of Kabul
- Identification, technical and environmental evaluation of potential sites for a sanitary landfill (see the Kabul map, left)
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For the identification of a site suitable for a sanitary landfill the following 'road map' had been followed:
- Description of the actual situation
- Geographic, topographic and demographic situation of Kabul
- Climatic conditions
- Hydro-geological and geological situation in the Kabul Basin
- Groundwater
- Soil quality and land use
- Generation and disposal of municipal solid waste (MSW) in Kabul
- Quantity and quality of MSW
- Collection and transport of MSW
- Current sites for waste disposal in Kabul
- Identification of a new sanitary landfill site
- Identification of site areas
- Environmental impact assessment of landfill sites and comparative site rating
Six potential sites were found in the Kabul region. By an investigation of the hydro-geological situation in the Kabul Basin it was possible to exclude areas with high groundwater vulnerability (high soil permeability and high groundwater table). By a comparative environmental assessment of the six identified sites it was possible to reduce the number of potential sites from six to one (see Table 2, left).
