INVESTIGATION METHODOLOGY FOR UNCONTROLLED LANDFILLS

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1 INVESTIGATION METHODOLOGY FOR UNCONTROLLED LANDFILLS MAVROPOULOS ANTONIS *, KALIAMPAKOS DIMITRIOS** *: EPEM Ltd., Solid Waste Management Department - 34A Averof str., N. Ionia, Athens, Greece, **: National Technical University of Athens (NTUA), Department of Mining Engineering & Metallurgy, 9 Heroon Polytechniou str., Zografou , Greece SUMMARY: Thousands of uncontrolled landfills should be restored in Greece and a lot of billions drachmas have already been spent for such activities. The most usual problem for the design of a restoration plan for uncontrolled landfills is how to estimate the environmental impacts, without knowledge of all the critical parameters that are known in the case of a normal landfill (e.g amount and composition of waste, aging of waste body etc.). This problem can be solved with the development of an investigation methodology which will provide all the necessary information, spending the minimum money. The first step of this methodology is the definition of the minimum inputs that are necessary in order to estimate the environmental impacts and to create a restoration plan. The second step is the selection of appropriate investigation methods and finally there must be a data acquisition scheme which will correlate the investigation results with the minimum inputs. The results of this methodology at the case of Skafidaras uncontrolled landfill confirm that it is an effective engineering tool. 1. INTRODUCTION Dumping on land has been one of the most widely used methods for the final disposal of solid wastes. In Greece open dumps became a common method to dispose of solid wastes for a long period of time. Out of 4639 solid waste disposal sites in Greece (in 1993), 3099 (66,5 %) are officially recognized as uncontrolled landfills, according to the Ministry of Environment Physical Planning and Public Works. Thus, the restoration of thousands of uncontrolled landfills in Greece is an urgent, complicated and difficult problem. During the last three years, more than 6 billion drachmas (almost 20 million ECUs) have been spent for restoration of uncontrolled landfills. In all these cases, a common question is how to estimate the environmental impacts of uncontrolled landfills. When engineers have to design a restoration plan for a normal controlled landfill, they have to find technical solutions about the final landscape morphology, the biogas and leachate management etc. In order to find these technical solutions they have to estimate a lot of parameters and to specify the migration paths of biogas and leachate. In this case, there is a single route (solid line in Figure 1): using the available data, they make the data analysis and then they design a restoration plan. In contrast, when engineers have to design a restoration plan for an uncontrolled landfill (which is a typical Greek case), they often face up that there is no available data (Mavropoulos, Kaliampakos 1999).

2 *: start point for a controlled landfill **: start point for an uncontrolled landfill Minimum inputs : procedure for a controlled landfill : procedure for an uncontrolled landfill Data analysis Investigation methodology Available data * Data analysis Development of a restoration plan ** Figure 1: Procedures for the restoration plan of controlled and uncontrolled landfills In fact, they have to find the same technical solutions as if they have to work on a controlled landfill, but without the required information. In this case, there must be a double route (distinct line in Figure 1). First they have to determine the needs for data analysis and estimations. Then, they have to determine which are the minimum inputs in order to proceed to data acquisition. Finally, they have to find out how to gain these inputs and they can go in reverse. The key point at this case is the definition of the minimum inputs. The precise estimation of the necessary data and the complete investigation of an uncontrolled landfill presuppose very high budget, which is usually unavailable. Thus, the practical question is how to get the necessary level of information (minimum inputs) that guarantees a safe and successful restoration plan, spending the minimum money. There is not a simple and complete answer to this question, further more there is not a unique answer. So what engineers need is an effective and flexible methodology to standardize the process of uncontrolled landfill investigation. Such a methodology (Mavropoulos, Kaliampakos 1999) has been developed and tested with high effectiveness at two complicated cases of uncontrolled landfills in Greece (Kareas landfill in Athens and Skafidaras landfill in Crete). This methodology consists of three steps: the definition of the minimum inputs, the selection of the appropriate investigation methods and a data acquisition scheme. 2. THE DEFINITION OF THE MINIMUM INPUTS The environmental impacts of an uncontrolled landfill are closely related to: The composition and quantity of the disposed solid wastes. The conditions that controls the mechanical, biological, physical and chemical changes inside the waste volume. The main physicochemical decomposition processes operating within the waste volume. It must be also noted that, uncontrolled landfills are very uneven systems and much depends on location, composition of wastes and the existing climatic conditions. Consequently, every uncontrolled landfill is a unique case (Little et al, 1995). The definition of the minimum inputs and the data resources is the result of the reverse route analysis (see Figure 1). The proposed methodology starts with the answers to the following questions.

3 What are the separate activities and decisions that determine the environmental part of a restoration plan for an uncontrolled landfill? In a general case, it is considered that the environmental part of a restoration plan consists of the six-(6) different categories of activities. First of all, one has to decide about the final landscape morphology (category 1), considering stability, environmental and aesthetics parameters. The second step is the top cover selection (category 2). This is a key selection, because it is directly correlated with the biogas, leachate and surface water management (category 3,4,5 correspondingly), which are the next steps of the restoration plan. Afterwards, the monitoring system (category 6) comes, as the tool that controls the efficiency of all the previous activities and integrates the environmental part of a restoration plan. What should an engineer find out (at least) in order to design the environmental part of a restoration plan? First of all he has to find out which was the initial landscape morphology (before the disposal of waste) and which is the landscape alteration due to the disposal of waste. This is necessary for the estimation of waste amount, settlements and the allocation of all the rest works and activities. Most of the times, the initial landscape morphology and the way that the waste was disposed off indicate the migration paths for biogas and leachate emissions. These migration paths have to be known and well understood for the successful allocation of biogas and leachate management systems. At any case, there is a need for estimation of the produced leachate and biogas amounts and an approach for their chemical composition. Especially for the leachate management, it is also necessary the estimation of surface water balance, before and after the top cover installation. Which are the minimum inputs (necessary data) for the previous estimations and findings? There are some general data (climate, geological and hydrogeological data, the way that the waste body was constructed etc.) that must be collected. Considering that this kind of data is available, the most significant questions are: What is the waste amount and composition? What is the aging of waste? What particular conditions mainly exist inside the waste mass? I.e.: Are the waste compacted and what is the compaction ratio? Do aerobic or anaerobic conditions exist? What is the temperature and the pressure inside the waste mass? What are the water conditions inside the waste mass? What are the main physicochemical, biological and mechanical processes controlling the landfill? What are the spatial alterations inside the waste volume? The answers to the previous questions are the minimum inputs in order to assess the environmental impacts of an uncontrolled landfill and consequently to design the environmental part of the restoration plan. Table 1 shows the correlation between minimum inputs, necessary estimations and findings and the development of the environmental part of a restoration plan. In Table 1 also, someone can find links between different categories of data and specific uses of them. These links have a general application at restoration plans. It must be noticed that Table 1 can be much more detailed. Also sometimes there is a need to create tables like Table 1 for separate activities e.g. the biogas management or the monitoring system. That depends on the specific problem of each case but the general guide line, for every case, is to start the creation of such tables from the right to the left.

4 Table 1: Correlation between minimum inputs, estimation - findings and the restoration plan NECESSARY ESTIMATIONS AND FINDINGS BIOGAS MANAGEMENT LEACHATE MANAGEMENT : Correlation between estimations - SURFACE WATER MANAGEMENT findings and the restoration plan TOP COVER FINAL LANDSCAPE MORPHOLOGY MONITORING MINIMUM INPUTS Landscape alteration Biogas calculations - migration Leachate calculations - migration Surface water balance Estimation of settlements ENVIRONMENTAL CATEGORIES OF A RESTORATION PLAN WASTE AMOUNT WASTE COMPOSITION WASTE CONDITIONS (compaction,t,p, water, moisture etc) GEOMORPHOLOGY, GEOLOGIGAL & HYDROGEOLOGICAL DATA : Correlation between minimum inputs and necessary estimations and findings CLIMATE NECESSARY ESTIMATIONS AND FINDINGS

5 3. SELECTION OF INVESTIGATION METHODS AND DATA ACQUISITION Figure 2 shows the correlation between minimum inputs and the data resources and the proposed data acquisition scheme. In Figure 2, someone can find also some critical parameters, like the C/N or the BOD/COD ratio, that should be estimated and give valuable information about the processes inside the landfill and the aging of the waste. QUESTIONS 1. Waste composition: organic C%, C/N RESOURCES Waste sources Sampling and analysis 2. Waste conditions: P, T, Humidity, Compaction, air and water presence Biogas measurements, pumping test Sampling Drills Geophysical Research 3. Processes that control the waste degradation Biogas measurements, pumping test Leachate analysis: BOD/COD, C/N Answer to Question 1 4. Data acquisition process 4.1 Estimation of organic C% and aging of waste CROSS-CHECK Answer to Question 2 BOD/COD (leachate) C/N (solid waste, leachate) 4.2 Aerobic or anaerobic degradation (mainly)? Spatial alterations 4.3 Main migration paths for biogas and leachate 4.4 Estimation of settlements, biogas emissions and leachate production rate Biogas measurements - Combination of the available results from answers to question 2 and 3 Autopsy, biogas measurements, pumping test, drills, geophysical research, general data 5. Allocation of leachate and biogas management facilities, selection of top cover, allocation of monitoring facilities, formulation of the restoration plan Figure 2: Correlation between minimum inputs, possible data resources and acquisition scheme Using the Figure 2 route, someone can adapt each specific needs and financial resources to the different alternatives that are included in Figure 2. The main idea about data acquisition is to check every estimation with data became from different resources. So every point estimation will be as certain as the used data resources. Another characteristic is that using this methodology, someone will gain adequately safe estimations, instead of precise ones. The combination of Table 1 and Figure 2 provides a methodology that can be used in every time there is a need for a landfill investigation. The main advantage of this combination is that

6 indicates not only a way to investigate the landfill but also a standard way to exploit the results and develop a restoration plan. As it is obvious at Figure 2, the proposed methodology gives a special role to the biogas measurements. Due to underground migration of biogas, biogas measurements are more indicative of the entire physicochemical processes than the local conditions (Straka F. et al, 1993). Also biogas measurements are relatively inexpensive. Thus, the proposed methodology suggests that the main part of an uncontrolled landfill investigation should be an extended program of biogas measurements. A borehole grid should be installed at the landfill, with the borehole positions as representative as they can be. At these boreholes, biogas measurements must include chemical composition (CH 4, CO 2, CO, H 2 S, O 2 ) and a pumping test at least. The proposed methodology suggests that the biogas measurements program must be combined with other data resources for the creation of a reliable picture of the landfill. The selection of the other data resources depends on the available data and the financial resources. 4. RESULTS: SKAFIDARAS LANDFILL The old landfill of Herakleion (Crete) is located at the site Skafidaras, 8 km outside the city. This site contains about tones of waste and it was used from The landfilling was absolutely uncontrolled (no liners, no biogas or leachate management systems etc.). The initial morphology of the area was not known in details. No investigation of the landfill had been done, although there was a restoration plan, proposed from the local authorities. The total budget for the restoration works is 1,7 million ECUs. Using the proposed methodology (Table 1 and Figure 2), the investigation methods were selected and Table 2 was created. Table 2: Correlation between necessary data and data resources at Skafidaras landfill NECESSARY DATA Waste amount Waste composition Waste aging Waste volume conditions Compaction Air presence Temperature, pressure Water infiltration Biogas Meas/ments DATA RESOURCES Temperature Drills Leachate - Pressure sampling Meas/ments SW sampling Four (4) boreholes (depth from 9-30 m) and sixteen (16) monitoring wells (depth: 6m) were installed at a m 2 area. Fifty (50) solid waste samples were taken from the boreholes. 10 leachate samples were also analyzed. An extended program of biogas measurements at the boreholes and the monitoring wells was implemented. The duration of the program was two months and it was completed with a pumping test. All the results were put on a topographical map and so a diagnostic map was produced with the biogas and leachate migration paths, the spatial alterations of the waste volume processes and the solid waste height.

7 For the identification of the biogas migration paths, diagrams like Figure 3 were produced with the results of biogas measurements. For each borehole and monitoring well were produced 5 diagrams with the results of CH 4, CO 2, CO, O 2, H 2 S measurements. Figure 3 shows the methane concentration inside the four boreholes during the first twenty days. % v/v METHANE G1 G2 G3 G DAYS Figure 3: Methane concentrations inside the four boreholes at Skafidaras landfill The main results from the investigation are: Organic carbon is estimated at 6-7% w/w. The disposed waste degradation is significant. That was confirmed from the leachate analysis which resulted a BOD/COD ratio equal to 1/21 and ph around 8. Aerobic processes were identified at three areas. The rest of the landfill is dominated by anaerobic processes. Humidity and biogas measurements confirm the existence of areas with uncompleted aerobic and anaerobic processes. The expected biogas production for the next 15 years was corrected from m 3 to m 3, using the investigation results and mathematical models (Arigala et al, 1995). The expected maximum leachate production was also corrected from 300 to 550 m 3 /day, due to the detailed stratigraphy that was identified with the boreholes and monitoring wells. The expected settlements estimated at 0,8m for the next 10 years for the central part of the landfill ( m 2 ), although the impression was that settlements were completed. Due to these results, the restoration plan was designed again. More specifically: The biogas management system was re-allocated according the identified migration paths and its capacity was corrected. The leachate management system was re-allocated according the identified migration paths and its capacity was corrected The playgrounds and some buildings that were going to be constructed at the site, after the restoration works, were re-allocated to areas with minimum settlements. The cost of the investigation program was about ECUs, that means 4% of the total budget or about 800 ECUs per 1000 m 2. This cost is relatively low and it is almost the same comparatively with the investigation cost of Kareas landfill.

8 5. CONCLUSIONS Uncontrolled landfills are an undesirable activity in MSW management, but they have been the most widely used way of waste disposal for many years. Especially in Greece, the rehabilitation of such landfills is an extremely urgent task. The restoration of uncontrolled landfills is a complicated scientific and technical problem, mainly due to the lack of information and the great heterogeneity of the processes inside the waste mass. Furthermore, scientific knowledge about dumped waste behavior originates mainly from sanitary landfills or laboratory experiments and it is very difficult to simulate a real uncontrolled landfill based on this knowledge. The proposed methodology targets to define the minimum inputs required for a restoration plan and to determine the appropriate investigation program, using limited financial and data resources. The definition of the minimum inputs is the key point to the whole procedure. Figures 1-2 and Tables 1-2 present the logical sequence of the methodology. Using this methodology in the cases of Kareas and Skafidaras landfill, it is proven that it is effective not only to provide the required data but, also, to exploit the investigation results. The main characteristics of this methodology are: the distinct definition of the minimum information required the links between different categories of information and the specific use of them the objective of gaining adequately safe estimations, instead of precise ones the basement mainly on the results of methods examining the overall characteristics of the landfill, such as biogas measurements, instead of, for example, the local sampling REFERENCES Arigala S., Tsotsis T., Webster I., Yortsos Y. (1995) Gas Generation, transport and extraction in landfills, Journal of Environmental Engineering, vol. 121, N.1, p Little R.H., Torres C, Towler P.A., Simon I., Aguero A. (1995) Long term environmental impacts of landfills using safety assessment comparison methodology, Fifth International Landfill Symposium, Proceedings Sardinia 95, p.443 Mavropoulos A., Kaliampakos D. (1999) Uncontrolled landfill investigation: a case study in Athens, Waste Research and Management, under publication Straka F., Crha J., Kobrova Y. (1993) Important changes in sanitary landfills during their aging, Fourth International Landfill Symposium, Proceedings Sardinia 93 I, p.573

Solid Waste Management in Greece: large steps forward

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