Geotechnical Aspects of a Landfill Site Selection Study in North Evia - Greece

by

O. G. Manoliadis

Technological Educational Institute
Department of Geotechnology and Environmental Engineering
Koila 50100 - Kozani, Greece

K. I. Sachpazis

GEODOMISI S.A.32 Marni Street, Athens

 

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ABSTRACT

In Greece Sanitary landfilling is the most common way of disposing of municipal solid wastes. One of the major problems in waste management nowadays concerns the selection procedure of the most appropriate site for their final disposal. In this paper a two-stage, multicriteria evaluation is presented. In the fist stage, in order to establish the promising sites, waste disposal is merely based on geotechnical criteria as it touches upon issues of the geoenvironment and the landscape as well as the suitability of geoenvironment for siting is depending mainly on its stability and on the danger of groundwater pollution. In the second stage these sites are evaluated using economic efficiency, environmental and technical economic criteria. It is interesting that the method sets the factors clearly and helps experts and local communities to participate. The method is easily applicable to a new landfill site. Its selection in Northern Evia and the results were accepted by the local communities.

KEYWORDS: land fill site selection, multi criteria evaluation, geotechnical criteria

 

INTRODUCTION

The district of Northern Evia has decided in the construction of a waste disposal site. The 13 municipalities to be served selected by same geomorphological characteristics and geographical position have a population of 10431 habitants. The corresponding production comes up to 3464 tons per year.

This district is located from Prokopi  to the Northern part of the inland (Istiaia) in Central Greece (Figure 1). The region of Northern Evia where the new municipal landfill should be situated, basically consists of a hilly-mountainous part and the Xirias  river valley part.

 


Figure 1. Study area

 

Most of the non-hilly, non-mountainous part is restricted for landfill construction because of existing nature protection zones, water sources protection zones. Also some theyrmal water protection zones of nearby spas Aidipsos have to be respected. Most of the Xirias river valley part is considered to be a potential flood-plain, also restricted for landfill construction. Also that part is densely populated, comprising a chain of villages with the Istiaia city in the center.

The criteria to be evaluated in this matter and to be depicted on the land suitability maps are reported in Hasna (1996) (see Table 1). Though there numerous criteria used for evaluation (ref work Landfill Criteria For Municipal Solid Waste Municipal Waste Reduction of The Environmental Protection Compendium (1993) the ones used here representing local factors are classified according to in geotechnical, environmental, economic and technical as follows.

 

GEOTECHNICAL CRITERIA

The degree of the danger of groundwater pollution in waste disposal subsoil is determined mainly by geotechnical criteria i.e. the quality and the structural arrangement of the aquicludes and aquifers occurring near the land surface which, affecting at the same time the cost of protective technical measures necessary for groundwater protection.

If a natural sealing layer (an aquiclude) overlies the aquifer the danger of groundwater pollution and possibilities of its prevention depend mainly on the quaylity and the thickness of the aquiclude, and, on the degree of transmissivity of the aquifer.

If a permeable layer (an aquifer) is at the land surface and overlies an aquiclude, the danger of groundwater pollution is proportional to the transmissivity of the aquifer and the possibility of an economically feasible groundwater protection depends mainly on the aquifer thickness or on the depth to the surface of the underlying aquiclude.

The classification system (Hasna, 1993) for geoenvironment evaluation from this point of view is given in Table 2.

Danger of groundwater pollution and/or costs of remedial measures Structural arrangement of aquicludes and aquifers danger of groundwater pollution and/or cost of protective measures. The first two categories induce unsuitability and the third one the conditional suitability of the geoenvironment for waste disposal siting. The fourth and fifth category present suitable conditions for waste disposals development.

Besides the aquifers transmissivity, the type of their permeability can be included into the complex symbol of the geoenvironment. This makes it possible to determine the way of infiltration, circulation and accumulation of groundwater, and, the conditions for technical works preventing its pollution, as well.

The applied classification system enables to express also the aquicludes inhomogeneity and the shortage of date about the thickness or position of the underlying aquicludes (see the table).

Type of aquifers permeability Examples of geoenvironment complex symbols. The characterization of the sites is depending upon the aquicludes thickness or the depth to the surface of aquicludes, used in the table, on the one hand reflect their retardation capacity and on the other hand correspond with the strata thickness presented on engineering geological maps. This enables their easy transformation for the given purpose. The classification system of the aquifers transmissivity presented in the table is in harmony with that one currently used by the compilation of hydrogeological maps.

Table 1. Geotechnical criteria
Criteria Index
Aquifer thickness e11
Permeability e12
Infiltration-Percolation e13

ENVIRONMENTAL CRITERIA

Cover and final cover for landfill sites is to consist of a minimum of low permeability (<1 x 10 - 5 cm/s) compacted soil plus a minimum of 0.15 meter of topsoil with approved vegetation established. The depth of the topsoil layer should be related to the type of vegetation proposed (i.e. rooting depth). Soils of higher permeability may be approved based on leachate generation potential at the landfill site. Final cover is to be constructed with slopes between 4% and 33% with appropriate run-on/run-off drainage controls and erosion controls. An assessment of the need for gas collection and recovery systems shall be made so that, in the event such systems are required, cover can be appropriately designed and constructed. Final cover is to be installed within 90 days of landfill closure or on any areas of the landfill which will not receive any more refuse within the next year. Completed portions of the landfill are to progressively receive final cover during the active life of the landfill.

Additional layers of natural materials including earth and aggregate and/or synthetic materials may be necessary for inclusion in the final cover design due to site specific conditions and the presence of management systems for leachate and landfill gas (e21).The aesthetics play a significant role in the design of landfill. Absence of landfill intrusion (e22).Landfills must not be operated in a manner such that gas emissions create a public odor nuisance, or that federal, provincial or local air quality criteria are exceeded (e23). A landfill must not be operated in a manner such that a significant threat to public health or safety or a public nuisance is created with respect to: unauthorized access, roads, traffic, noise, dust, litter, vectors or wildlife attraction (e24).

Table 2. Environmental criteria

Criteria Index
Land cover and ecological character e21
Absence of optical intrusion e22
Odors nuisance e23
Public health, safety and nuisance e24

 

ECONOMICAL, LAND USE, AND SOCIAL CRITERIA

Net present value and Depreciation cost are used to evaluate the total profitability of the project’s alternative sites (e31, e32) The impacts on housing tourist development of the project is calculated in monetary units and classified in a scale from 1 to 10 (e32).

Table 3. Economical criteria
Criteria Index
Net present value e31
Depreciation cost e32
Impacts in housing/touristic development e33

 

TECHNICAL OPERATIONAL CRITERIA

Landfill capacity is dependant upon the actual life of the facility and is dominant for any decision process.(e41).The availability of the appropriate cover material is also taken into consideration. Soils of low permeability approved based on leachate potential of the facility are desirable.(e42).An appropriately constructed and maintained access road to and a road system within the landfill site capable of supporting all vehicles hauling waste are required during the operating life of the landfill.(e43). The distance between the landfill site and places of waste consumption (e44).

Table 4. Technical Operational criteria
Criteria Index
Landfill capacity e41
Cover material availability e42
Access roads e43
Distances from the Waste consumption e44

 

Finally the following are the ratings of each criterion (see Table 5).

Table 5. Ratings of criteria
Criteria
A (1-2)
B (3-4)
C (5-6)
D (7-8)
E (9-10)
Aquifer thickness (GE1)
Very High
High
Medium
Low
Very low
Permeability (GE2)
- - - - -
Infiltration Percolation (GE3)
porous
fissure-porous
fissureous
fissure-karst
karst
Land cover
and ecological
character (EN1)
Very good
Good
Medium
Bad
Very bad
Optical intrusion (EN2)
Very good
Good
Medium
Bad
Very bad
Odors nuisance (EN3)
Very good
Good
Medium
Bad
Very bad
Public health, safety and nuisance (EN4)
Very good
Good
Medium
Bad
Very bad
Net present value (EC1)
Very good
Good
Medium
Bad
Very bad
Depreciation cost (EC2)
Very good
Good
Medium
Bad
Very bad
Landfill capacity
Very Large
Large
Medium
Low
Very low
Cover material availability
- - - - -
Access roads
Very good
Good
Medium
Bad
Very bad
Distances from the main source of residents, public places, Waste consumption
- - - - -

 

METHOD OF ANALYSIS

The steps of the method used consist a two stage, multicriteria methodological framework which is presented in the following paragraphs. The paper presents a theoretical analytical framework to guide the site selection process for this kind of facilities and provides an illustrative case study application

 

First stage

The method used in the first stage is described in Hasna (1996). First, geological maps at a scale of 1:200 000 are compiled. Their purpose is to serve as preliminary source of information for local authorities and other users about the possibilities of waste disposal siting and about the environmental impact of old landfills, as well.

Land suitability maps for waste disposal siting (of both above mentioned scales) consist of three parallel map sheets. Two of them are documentation maps which comprise all data needed, the third one is the proper land suitability map elaborated on the base of zoning.

The first documentation map includes all legally protected areas: nature reserves, protected forests and mineral resources, protective zones of potable, mineral and thermal water resources and some other hydrological phenomena. The second documentation map represents the danger of groundwater pollution expressed by the complex symbols of the geoenvironment and the geodynamic phenomena affecting the land use. The nearest residence, water supply well, water supply intake, hotel, restaurant, food processing facility, school, church or public park is to be a minimum of 300 meters. Greater or lesser separation distances may be approved where justified. For those landfills designed to collect and recover methane gas generated, the issue of potential on-site or off-site users of the energy should be addressed in siting the landfill, consistent with the preceding regarding public places. The distance between an airport utilized by commercial aircraft and a landfill containing food wastes which may attract birds is to be a minimum of 8.0 kilometers, unless bird control measures acceptable international standards.

The zoning map (or land suitability map) is compiled on the base of two previous maps. It divides the mapped area into suitable, moderately suitable and unsuitable territorial units (zones) taking into account the degree of legal protection, the risk of groundwater pollution and presence of hazardous geodynamic phenomena.

Besides the main purpose ( which follows the name of the maps ), the maps of land suitability for waste disposal siting provide the basic information about the geological conditions of new landfills building and about the conditions of reclamation the old ones, as well. This follows mainly the complex symbols of the rock environment and the data about other geofactors, mainly of geodynamic phenomena. As a result the proposed sites are derived.

 

Second stage

The suitability of the territory for waste disposals is not evaluated on the maps in whole. It is only the partial suitability which extent is given by the range of the factors taken into account by their compilation. At selection of suitable sites for waste disposals, it is necessary to take into consideration further factors which cannot be represented on the maps of the small and medium scales (such as protective zones of airports, railroads, etc.) and those which are connected with the distance of sites from water courses and reservoirs, urban areas, etc. The problem consists a multicriterion decision making process where the criteria to be considered are environmental, economical and technical.

The methodology used in this research was Compromise programming. The method a linear multiobjective programming (MOP) technique is described originally by Zeleny (1974). This technique allows one to find the complete set of efficient solutions from two or more objectives finding the most appropriate solution from this set of efficient solutions. The efficient set includes all feasible non dominated solutions, i.e. all the pareto optimal solutions such that no better outcome can be achieved without making at least one objective worse off. An ideal solution is specified with co-ordinates by the optimal values for each objective. Using this solution as reference the compromise technique allows selection of the compromise set, i.e. the set of feasible efficient solutions closest to the ideal solution. The optimal solution depends on the distance function and the compromise set, is composed of the optimal solutions from the following minimisation problem

(1)

where Lr indicates the distance measured and R(i) is the ideal value.

ai and aj the relative weights described below.

The compromise programming algorithm used in the current research is capable of handling a large number of objectives into series of lower dimensions in order to gain a deeper understanding of the inter-relationships of the subsystems . Selection of the specific was not arbitrary since it was based on decision makers’ prior knowledge and experience about the site as well as previous experience of landfill sites.

After these basic criteria have been identified, the process of building the management system from its elementary components by defining the structure of the compromise programming model begins. The process can be characterised as grouping the basic criteria into clusters based on either similar characteristics or the desire to contrast different features through trade-off analysis.

The initial set of corresponding indicators that result from grouping are called first level indicators. After the first level indicators have been specified, the grouping process continues until the highest level indicators have been specified. In the case of the landfill site selection this final level may describe the trade-off between environmental and economic interests.

 


Figure 2. Compromise programming structure

 

There are two kinds of weights assigned (ai and aj). The weight assigned to the particular management performance index reflects the relative preference to other elements within the same group and the weight assigned to the preference to the trade-off analysis (Fig 2) Therefore, compromise programming uses a double weighting scheme to reflect the importance of the maximal deviation between the indices used. Then the decision maker must specify a value for the balancing factors.

The impact relationship is a measure of the basic index value for each of the management options and serves as an input to the management system model.

Evaluation of the alternatives is accomplished by calculating the distance of the ideal point. The preferred management option is then identified from the candidates by locating the system nearest the ideal point.

 

Combination of the two stages

The impact relationship R(x) is a key link between composite programming and impact assessment of alternative sites using environmental indices. Impact relationships (equation 1) are measures of basic index values for each alternative in terms of system performance. Once an alternative is identified the impact relationship R(x) is obtained, used as an input to the compromise programming algorithm as a data table in the discrete case of alternatives that is examined.. Analysis of the results may proceed after all compromise distances have been computed. Consequently it is possible to characterise the areas surrounding the ideal state based on a radial distance from the ideal point. Using the exclusionary criteria, although the limits are somewhat subjective and the values may be modified, the area is divided into desired acceptable and non acceptable regions.

 

APPLICATION - RESULTS

Results of the first stage-Suitability maps and proposed sites

The land suitability maps for waste disposal siting at a scale of 1:50 000 have been prepared from a background based on HAGS by the Army Crops of Greece. Due to their greater capacity and detailness these maps can give more complete and precise information. The information that this background gives is presented in Table 6.

With regard to the smaller capacity of the maps at the scale of 1:200 000, some simplifications were done by their compilation. The transmissivity of aquifers was evaluated in four degrees (the transmissivity marked as D and E in the table 2 are put together) and the thickness of the aquicludes in two degrees only. The structural arrangements in which the superficial stratum is formed by an aquifer with the thickness of more than two meters are regarded as unsuitable in these maps.

In Table 6 the characteristics of proposed sites (i.e. visual contact, altitude, access road, hydrogeological, land use vegetation and livestock ) are presented. The landfill sites position is presented in Figure 4.

Table 6. Landfill site characteristics.
Site Name Visual contact Altitude (m) Access road Live-
stock
Vegetation Hydro-
geological
Land Use
ISTIAIA
(Elitsa)
Yes 620 Asphalt road N Y Not-permeable Annual Crops
AIDIPSOS
(Lithsyrtis)
No 720 Asphalt road N Y Not-permeable Annual crops
ELLINIKA
(Kalyvia)

No
770 Road N Y Semi-permeable Annual crops
MANTOUDI
Paraskevorema
Yes 700 Asphalt Road N Y Not-permeable None


Figure 4. Land suitability map and proposed sites

 

The estimation of environmental indices is presented in Table 7.

Table 7. Values of environmental indices
CRITERIA
ELITSA
AIDIPSOS
ELLINIKA
MANTOUDI
Aquifer thickness
8
7
8
8
Permeability
8
7
7
8
Infiltration Percolation
7
8
8
7
Protection of ecosystems and water resources
10
5
7
7
Absence of optical intrusion
10
6
8
7
Odors nuisance
10
5
7
7
Public health, safety and nuisance
9
7
7
7
Net present value
10
7
9
8
Depreciation cost
9
7
7
8
Impacts in housing/touristic development
10
5
7
7
Landfill capacity
7
8
8
7
Cover material availability
7
5
7
7
Access roads
6
7
6
7
Distances from the Waste consumption
10
7
5
4

 

Table 8 summarizes the weights assigned to each index for the compromise programming

Table 8. Weights assigned
Criteria Index First level Second level
Geotechnical ei11 w11 = 0.33 w1 = 0.2
ei12 w12 = 0.33
ei13 w13 = 0.33
 
Environmental ei21 w14 = 0.25 w2 = 0.4
ei22 w21 = 0.25
ei23 w22 = 0.25
ei24 w23 = 0.25
 
Economical ei31 w31 = 0.20 w3 = 0.3
ei32 w32 = 0.20
ei33 w33 = 0.60
 
Technical-Operational ei41 w41 = 0.20  
  ei42 w42 = 0.30 w4 = 0.10
  ei43 w43 = 0.10  
  ei44 w44 = 0.40  

 

Table 9 summarizes the results of the compromise programming for the four alternatives examined.

 

Table 9. Results
CRITERIA ELITSA AIDIPSOS ELLINIKA MANTOUDI
GEOTECHNICAL 7.59 7.26 7.59 7.59
ENVIRONMENTAL 7.25 5.75 7.25 7.75
ECONOMICAL 9.20 7.00 7.40 7.80
TECHNICAL-OPERATIONAL 6.70 5.00 4.70 4.40
SCORE 7.848 6.352 7.198 7.398

 

Examining the results in terms of the first management option Express a strong concern for environmental quality alternative 4 is ranked first (7.75) followed by 1 and 4 (7.25 ).

 


Figure 5. Geotechnical criteria

 

Finally in terms of geotechnical criteria alternatives 1, 3 and 4 (7.59) ranked first followed by 2 (7.26), as shown in Figure 6.

 


Figure 6. Ranking according to economic criteria

In terms of economic criteria alternative 1 (9.20) is ranked first followed by 4 (7.80).

 

In terms of the technical operational criteria alternative 1(6.70) followed by 2 (5.00), as shown in Figure 7.


Figure 7. Ranking in terms of the technical operational criteria

 

The score of each alternative computed as the relative distance of the ideal solution, assuming the weights assigned to each index (Figure 8) is as follows: 1(7.85), 2(6.55), 3(7.20), 4(7.40)


Figure 8. Overall ranking

Therefore the solution is that ranks first to all management options is alternative number 1 since it has the closest distance from the ideal.

CONCLUSIONS

The method offers a two stage approach useful for environmental studies for landfill site selection.

In the first stage the maps of small scales make possible a simplified process of waste disposal factors evaluation regarding to their small capacity and detailness. Their goal is to provide the preliminary information on suitability of the territory for waste disposal siting and for estimation of environmental impact of old landfills, the majority of which belong to uncontrolled ones in Greece.

The maps of large scales are precisive to the previous maps and make possible the evaluation of those factors which directly affect the way of waste disposals building (mainly with respect to stability of geoenvironment) and the mode of groundwater protection

The fundamental base for waste disposal sites selection are the maps of medium scales which due to their greater detailness and capacity evaluate in a sufficient extent all relevant factors of land use for the given purpose and afford sufficient base for the application of multicriteria methods, as well.

The present work presents also issues of introducing a compromise programming approach into landfill sites selection. Two primary objectives that often conflict in sustainable development are economy of application and environmental performance. The final decision often involves a trade-off between these two objectives.

A case study has been presented to demonstrate the use of different objectives combined with compromise programming for solving the system selection problem within a multicriteria decision making framework. It should be noted that the methodology can be used in several cases of landfill management (development of existing sites, selection of alternative options). The approach used to select the final management alternative was to determine an alternative that is "the better existing alternative" with respect to different decision makers and possibly not the best for all management options. In summary, the present research extends previous efforts in landfill sites selection decision making using one stage objective approaches. It is felt that this extension using compromise programming provides a more realistic perspective of the management procedure.

These features combined with the social concern for landfill site selection warrant further investigation into decision support studies, multicriteria decision making approaches and the incorporation of the landfill sites selection.

Conclusively the proposed methodology: (1) allows for the consideration of more than one stages where preference criteria can be left in the final stage. The criteria in siting waste management facilities which belong to different hierarchical levels (stages) of the siting decision process; (2) places special emphasis on the geotechnical criteria both as regards the provision of specific environmental functions and attributes as well as regards the environmental impacts of these facilities; (3) offers a framework to deal with multiactor decision settings and conflict resolution; (4) provides for computer support of certain phases of the site evaluation and the group decision-making phases of the siting process; (5) it is simple and understandable, a feature especially important for its implementability.

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