Asset management is a strategic decision-making aspect of social infra-structure that ensures safety by predicting long-term conditions and maximizing effectiveness under budgetary constraints. Predicting the deterioration of impervious walls is essential in the asset management of coastal landfill sites, particularly in the design of their maintenance and repair strategy. In this paper, a quantitative evaluation of the leakage of toxic substances in coastal landfill sites where deterioration of side impervious walls has decreased the water interception performance is reported. In addition, risk evaluation based on the asset management of the leakage is applied to determine an appropriate repair method. The strategy of repairing the walls when the concentration of the toxic substances leaking into the sea area exceeds the closure and abandonment of coastal landfill sites is demonstrated to be superior. Moreover, the strategy of repairing only the seaside side impervious wall is shown to be cost-effective.
Landfill sites where nonrecyclable waste residue is reclaimed are examples of social infrastructure. Large-scale coastal landfill sites are being increasingly constructed in the harbour regions of urban areas in Japan (
When establishing the maintenance strategy for a coastal landfill site, the deterioration of a water-sealing is first predicted through high-temperature accelerated deterioration testing of the water-swelling material used in numerous steel side impervious walls. From the results, the amount of toxic substances leaking from site (i.e., total flux) is estimated and used as the decision-making standard. There are uncertainties in the deterioration prediction of impervious walls, and defining toxic leakage is hence difficult. Therefore, risk management- based leakage risk assessment for the total flux is conducted. Risk management is a technique that attempts to suppress to the extent possible the adverse effects of
the risk under budgetary constraints (
Landfill sites can be classified as least-controlled, controlled, and strictly controlled sites, and coastal landfill sites tend to be least-controlled or controlled sites [
fill sites. Furthermore, coastal landfill sites entail low risks of contaminating the head of a river.
Because coastal landfill sites face the sea, the difference in water level inside and outside the landfill must be appropriately controlled. In addition, layers of reclaimed waste in such sites can be classified as aquifer and nonaquifer layers, which exist below and above the water level, respectively [
Coastal landfill sites must be robust to external factors [
A steel-pipe sheet pile is often used as a side impervious wall. Such a wall is installed as continuous jointed sections (
specified toxic substances. When such materials are applied to the joints of the steel-pipe sheet piles, the solvent volatilises, leaving behind an elastic hard film. This film is impervious and thus improves the water interception performance of the joints. In this study, the water-swelling material used as the water interception treatment material is investigated.
Deterioration in the water interception performance of steel side impervious walls is believed to be due to the deterioration of the water-swelling material in the joints. In this study, temperature variation is assumed to be the main factor influencing the deterioration of the impervious wall. Other factors include reduction in durability due to chemical reactions and wet-dry cycles. Water- swelling materials do not react with chemical substances except trichloroethylene, dichloromethane, and carbon tetrachloride [
Water-swelling materials are expected to possess long functional lifetimes [
Strength is assumed to strongly influence water interception performance because swollen membrane strength and hydraulic conductivity have been previously associated. Specifically, strength decreases as the super absorbent polymer in the water-swelling material dissolves [
In the high-temperature accelerated deterioration test, the water-swelling material was immersed in high-temperature water, following which the strength of the swollen membrane was measured using an EZTest-500N (Shimadzu Corporation) with an elasticity jig of Φ3 mm, as described herein:
1) 80 mm × 80 mm × 2 mm specimens of the water-swelling material were prepared.
2) The specimens were immersed in a freshwater tank at water temperatures of 20˚C, 40˚C, 60˚C, and 80˚C.
3) The prepared specimens were placed between the upper part of the testing equipment and the lower acrylic plate, both of which are fixed to the equipment by using bolts.
4) The specimens were accelerated as indicated in
5) The specimens were removed from the water tank after predetermined periods of time (from 1 day to at most 43 days), and the strength of the swollen membrane at positions (stations) 15 and 30 mm from the centre of the specimens were measured at nine points in total (
6) The specimens were returned to the water tank.
7) Steps 5) and 6) were repeated.
The relationship between swollen membrane strength and number of days immersed is illustrated in
around the outer stations of the water-swelling material. The decrease in swollen membrane strength at each station increased with the increase in water temperature. Thus, deterioration of the water-swelling material is higher at higher water temperatures. In a previous study, water-swelling material immersed in
water at 20˚C for 10 years was reported to exhibit constant strength and water interception performance (i.e., swollen membrane strength of 0.8 N and hydraulic conductivity of 1.0 × 10−9 cm/s) [
The Arrhenius law is a physical deterioration prediction model in which the temperature is the main deterioration factor. In this model, the deterioration-induced reaction ratio can be expressed as Equation (1) and is inversely proportional to absolute temperature. Equation (1) is based on the reaction ratio kinetics that a reaction advances early at high temperatures [
where K is the reaction rate, A a constant (frequency factor), Ea the apparent activation energy, R the gas constant, and T the absolute temperature.
Given the reciprocal relationship between reaction rate and service life, expected service life (L) can be calculated using Equation (2).
On taking the natural logarithm of both sides of Equation (2), we obtai
where Ea/R and 1/A are constants. Because of the linear nature of this relationship, the reciprocal of the temperature and expected service life can be presumed to be and 1/T and ln L, respectively, meaning that the expected service life at room temperature (20˚C) can be predicted. The Arrhenius law yields the expected service life at room temperature; hence, performance deterioration up to end of the expected service life must be considered.
The durability of the water-swelling material is evaluated using experimental results and the Arrhenius law. However, because data acquisition of the frequency factor (A) is difficult and because apparent activation energy (Ea) is specific to the material, the expected service life―the period over which the material can maintain its initial water interception performance―cannot be calculated using Equation (2). Therefore, the time point at which the assumed ability of the water-swelling material is no longer evident is designated as the end of the expected service life. In this study, the time point at which the swollen membrane strength becomes less than 0.8 N is assumed to be end of the expected service life, because a swollen membrane strength of 0.8 N can support a hydraulic conductivity of 1.0 × 10−9 cm/s under an applied pressure of 0.5 MPa [
The approximated straight line plotted using Equation (3) shows the relationship between the reciprocal of expected service life (natural logarithm) and the temperature. The service life of the water-swelling materials at room temperature (20˚C) is interpolated from the results of accelerated deterioration testing at high temperatures (40˚C, 60˚C, and 80˚C) by plotting the results obtained at high temperatures in the 1/T-ln L plane.
Because the A and Ea of the material are constant, the slopes of approximated straight lines for the different temperatures should be approximately equal;
Average | Standard deviation | |
---|---|---|
Inclination (Ea/R) | 7439.8 | 1773.527 |
Section (ln 1/A) | −16.3922 | 5.1757 |
however, the results vary considerably (
In this study, the deterioration in water interception performance due to deterioration of the water-swelling material over its expected service life is examined by adopting hydraulic conductivity as an index of water interception performance. Previous studies [
Worst case (μ − σ) | Base case (μ) | Best case (μ + σ) | |
---|---|---|---|
Expected service life [years] | 9.14 | 21.90 | 52.50 |
of the water-swelling material is represented as an approximated straight line for the expected service life listed in
In coastal landfill sites, leakage of the retained water, which may contain toxic contaminants, occurs through infiltration, advection, and dispersion. These distinct phenomena must be accurately reflected in the estimation of the behaviour of the retained water at the side and bottom impervious walls. In addition, unlike inland landfill sites, the influence of external conditions such as tide must be accounted for in coastal landfill sites. Moreover, because impervious walls in coastal sites are complex structures composed of clays, sands, and steels, the characteristics of these constituents must be considered. Therefore, the deterioration prediction curved line (
layer of the landfill site. Moreover, the Euler-Lagrange finite element method, which combines Eulerian and Lagrangian methods and yields stable solutions for advection and dispersion, is used as the analysis code. Dtrans-3D・EL is used to visualise the unsaturated flow and advection-dispersion behaviours of groundwater and solutions.
The parameters of each constituent layer set are listed in
1) The steel side impervious wall is assumed to be a uniform layer, whose hydraulic conductivity is equivalent to that of the water-swelling material and the steel [
2) The penetration depth of the wall is assumed to be 3 m.
3) The parameters of the wall and the bottom layer (natural deposited clay layer) vary in each analysis.
4) The retardation factor (R) shows the adsorption ability of toxic substances and it is assumed to be 2 in the bottom layer [
5) No clear data is available for the molecular diffusion coefficient in coastal landfill sites. Hence, on the basis of three-dimensional infiltration and advection-dispersion leakage analysis of toxic substances in coastal landfill sites reported in [
6) Waste stabilisation is a long-term process, and the analysis period is therefore assumed to be 30 years; the landfill site is utilised after the landfill is closed or abandoned.
7) The difference in water level inside and outside the landfill site would not exceed 200 cm.
8) Infiltration and advection-dispersion parameters used in related studies [
Mass flux (mass per unit time and unit area) is the mass of toxic substances that passes through a certain section and is an index frequently used in charac-
Material | Hydraulic conductivity (Horizontal direction) kH | Hydraulic conductivity (Vertical direction) kv | Effective porosity θ | Longitudinal dispersion length αL | Transverse dispersion length αr | Coefficient of molecular diffusion Dm | Retardation factor Rd |
---|---|---|---|---|---|---|---|
Unit | cm/sec | cm/sec | cm | cm | cm2/sec | ||
Steel- made side impervious wall | 8.0 × 10−9 | 8.0 × 10−9 | 0.1 | 10 | 0.1 | 1.0 × 10−5 | 1.0 |
Bottom clay liner | 7.0 × 10−7 | 7.0 × 10−7 | 0.2 | 10 | 1.0 | 1.0 × 10−5 | 2.0 |
Filling sand | 1.0 × 10−3 | 1.0 × 10−3 | 0.2 | 10 | 1.0 | 1.0 × 10−5 | 1.0 |
Waste | 1.0 × 10−3 | 1.0 × 10−3 | 0.7 | 10 | 1.0 | 1.0 × 10−5 | 1.0 |
Sea area | 1.0 × 10−3 | 1.0 × 100 | 1.0 | 10 | 1.0 | 1.0 × 10−5 | 1.0 |
terising the movement of toxic substances [
Mass flux has three components: advection, diffusion, and dispersion flux [
where J is the mass flux, JA the flux related to advection, JD the flux related to diffusion, JM the flux related to dispersion, n the effective porosity, c the concentration, v the flow rate in the void, De the effective diffusion coefficient, and Dm the dispersion coefficient.
In this analysis, the total leakage volume (i.e., the total flux) from the steel side impervious wall and the bottom layer is calculated to evaluate the mass of toxic substances that leaks to the sea. The unit of total flux is [cm3] because this yields the dimensionless quantity of 1 for the concentration of toxic substances. Thus, the mass of the toxic substances can be determined by multiplying their concentration [mg/cm3] and total flux [cm3]. However, the concentration of toxic substances cannot be easily determined; therefore, total flux is used. Mass flux is the mass per unit area and unit time, whereas total flux indicates the total amount of toxic substances over the total outflow area and time [
A risk generally refers to an event that is undesirable, an occurrence of loss, or a clarification and is defined by a field and a target [
loss expectation value) can be defined as Equation (5) by multiplying the probability of the phenomenon and the loss level [
where R is the loss expectation value, Pi the probability of and Ci the loss due to phenomenon i, and J the total predicted loss.
In this study, the risk management was applied to reduce the risk in coastal landfill sites for the flow indicated in
1) Acceptance of waste: When the landfill site accepts waste, there exists a risk of the mixture of different materials.
2) Reclamation of waste: The risk of wastewater seepage is present even long after waste reclamation is complete. This environmental risk is one of the most damaging in landfill sites.
3) Maintenance of landfill site: Maintenance-related risks develop after the landfill site is closed or when the landfill site is no longer monitored (e.g., because of bankruptcy) risk is generated; this environmental risk is distinct from that of a natural environment.
In this study, the environmental risk pertaining to the leakage of retained water in coastal landfill sites (hereafter, leakage risk) is considered the most serious risk. This risk is controlled by constructing impervious walls. However, complete seepage prevention is technically difficult, which highlights the importance of reducing or managing leakage risk.
A quantitative understanding of the environmental risk is vital in the risk management of coastal landfill sites. Generally, the use value of risk management is high because the risks are easily accepted by all stakeholders when expressed in terms of monetary loss [
The fragility function is defined as the conditional probability of occurrence on a specified suffering scale. In earthquake risk analysis, this function is usually expressed as a probability density distribution of the damage probability, with earthquake magnitude on the horizontal axis and structural damage on the vertical axis. The probability of occurrence of the suffering scale corresponding to the magnitude of the seismic ground motion can be predicted by setting the limit state displacement to which the response displacement and structural damage caused by seismic ground motion occur as a probability density distribution.
In this study, the concentration and total flux of the toxic substances that leak into the sea area are used as indexes of leakage risk in coastal landfill sites. The probability of exceeding the limit reference set in these indexes is defined as a performance function (X) and a standard exceedance probability (FX) (Equations (6) and (7), respectively).
where X is the performance function, Ct the concentration or total flux of the toxic substances that leak into the sea area after t years, CA the limit reference setting for each index, and FX the standard exceedance probability. Because of nonnegative conditions, Ct and CA are expressed as lognormal distribution functions.
FX is the concentration of the leaking toxic substances calculated as a probability beyond the closure and abandonment of coastal landfill sites; it is assumed to be C = 0.1 in the present analysis.
Therefore, because the lognormal distribution function is set to the probability density distribution, FX is expressed as Equation (8). FX exceeds the specified limit reference value when uses t years of use passes is calculated. A similar calculation is repeated for an evaluation period of 30 years, and FX for the age of service and index is determined.
The average (λX) and standard deviation (ζX) of the performance function (X) can be led such by the median value and coefficient of variation of Ct and CA in Equations (9) and (10). These two parameters determine the sketch of the standard exceedance probability (FX).
where μCA is the median value in the limit reference set of each index, μCt the median value in the concentration or total flux of toxic substances leaking into sea area after t years of use, υCA the variation coefficient of the limit reference set of each index, and υCt the variation coefficient of the concentration or total flux of toxic substances leaking into the sea after t years.
The loss function Equation (11) is a function that yields the expected loss (R) corresponding to the damage level and the standard deviation of the expected loss [
where Pi is the probability that phenomenon i occurs, Ci the damage loss due to phenomenon i, and J the total number of phenomena.
In this study, the total flux of the leaking toxic substances is used as an index of the damage level of coastal landfill sites. In earthquake risk analysis, the suffering level of a structure is used for predicting the maximum response displacement of an earthquake and the judgment index of the repair method [
The occurrence probability of damage level k (Prob (k)) based on the total flux in the toxic substances that leak from any coastal landfill site can be calculated using the standard exceedance probability (Equations (6) and (7)). This probability must be expressed as a monetary value to facilitate comparison of risks; in this study, this conversion is performed using an endpoint modelling-based lifecycle impact assessment method [
where Ek is the damage cost related to the total flux of the toxic substances at damage level k, Jk the total flux of toxic substances at damage level k, ei the coefficient converted into a monetary value, and i the type of toxic substance.
Because the leakage of the toxic substances to the sea area in a coastal landfill site is investigated in this study, the coefficient is converted into a monetary value of discharge into unit area of the sea. Moreover, the damage coefficient accounts for damage to both the ecosystem and the human body. The expected loss value (NEL) relating to toxic substances in coastal landfill sites is
where Prob (k) is the damage occurrence probability at damage level k and Ek the damage cost related to the total flux of the toxic substances at damage level k.
The leakage risk of toxic substances considering uncertainties in the degradation of impervious walls in coastal landfill sites is estimated using the aforementioned risk assessment approach.
For evaluation the leakage risk of toxic substances in coastal landfill sites due to deterioration of impervious walls, the probability density distribution of each index is calculated. In addition, the standard exceedance probability and loss function are calculated for the worst-case, base, and best-case scenarios (
When the concentration of the toxic substances C that leak into the sea area is used as an index, C = 0.1 is set as the limit reference, and when the total flux of toxic substances that leaks into the sea area is used as an index, the limit reference is set at each damage level as listed in
With these assumptions, risk management can be applied to reduce leakage risk in the coastal landfill site, and the influence of each analytical condition on leakage risk can be quantitatively understood.
Damage level | Total flux of the toxic substances | |
---|---|---|
Rank-0 | Equivalent with no leaking of toxic substances. | 0 |
Rank-1 | Equivalent with 10% of the closure and abandonment of coastal landfill sites. | 1.65 × 106 |
Rank-2 | Equivalent with 50% of the closure and abandonment of coastal landfill sites. | 8.26 × 106 |
Rank-3 | Equivalent with the closure and abandonment of coastal landfill sites. | 1.65 × 107 |
Rank-4 | Equivalent with the technical guidelines of impervious walls. | 1.13 × 108 |
The leakage risks for different forms of steel side double impervious wall in a coastal landfill site with an internal and external water level difference of 200 cm is presented in
Generally, lognormal distribution is adopted in the risk assessment of nonnegative conditions. Moreover, because C = 1.0 - 0.0 is the relative concentration used in this study, the beta distribution that can set the upper and lower bounds is applicable. For the relative concentration of toxic substances leaking from the coastal landfill site targeted in this study, the aforementioned probability density distribution of two patterns is applied in the risk assessment because the compatibility of the probability density distributions was unclear.
15 years, that when using the lognormal distribution increases after an equivalent lapse. In other words, as the deterioration of an impervious wall progresses, the results (i.e., standard exceedance probability obtained using the lognormal distribution and that obtained using beta distribution) becomes increasingly conservative. This conservative approach ensures safety by adopting stricter evaluation criteria for the risk assessment of high-risk infrastructure such as nuclear power plants. Because the primary objective of this study is to reduce and manage leakage of toxic substances in coastal landfills, the conservative lognormal distribution is adopted. Nevertheless, the most appropriate probability density distribution must be determined through continuous monitoring of the concentration of toxic substances leaking from coastal landfill sites.
In a coastal landfill site, the leakage risk of toxic substances increases as side impervious wall deterioration progresses. Therefore, appropriate maintenance and repair must be performed to contain the toxic substances until the end of the wall’s intended life cycle. Although appropriate repair methods have been implemented in landfill sites (
When designing the maintenance strategy of social infrastructure, an appropriate repair method and time must be determined for appropriate asset management. Moreover, whether repairing is necessary must be determined through life-cycle cost (LCC) and cost-benefit analyses. Irrespective of the cost, repair becomes essential if environmental risk is demonstrated. In this study, deterioration of the side impervious wall is assumed to be the primary a factor that increases the environmental risk in coastal landfill sites, and repairing the side impervious wall is proposed as a countermeasure, with the leakage risk of toxic substances is adopted as a decision-making index. That is, an appropriate maintenance strategy that considers the decrease in the leakage risk according to the repair method is examined.
Social infrastructure maintenance strategy must consider such factors as checking intervals, performance level of the infrastructure repair (target level), and the adopted repair countermeasure [
The following assumptions are made in this analysis:
1) The cross-section of a steel side double impervious wall is used as the analysis model.
2) The evaluation period is 30 years.
3) The internal and external water-level difference in the landfill is 200 cm, and the relationship between the concentration distribution and total flux of the leaking toxic substances obtained in the preceding chapter is used.
4) The concentration, total flux of the toxic substances leaks, and the hydraulic conductivity of the side impervious wall are adopted as the judgment index for repair.
5) Strategies for repairing only the sea-facing steel side impervious walls and for repairing both the seaside and landfill site-side walls are proposed. Moreover, the steel side impervious wall is repaired only once.
6) The hydraulic conductivity of the steel side impervious wall after repair is assumed to have recovered to the initial level (
7) The maintenance strategy sets six patterns (
Judgment index | Time to repair | Repairing method | |
---|---|---|---|
No repairing | No repairing | ||
Plan-1 | Concentration | Point of time when the concentration at the sea area is more than it for the closure and abandonment of coastal landfill sites (C = 0.1) | Repairing the steel-made side impervious walls on sea-side only |
Plan-2 | Repairing the steel-made side impervious walls on the both sides (sea side and landfill site side) | ||
Plan-3 | Total flux | Point of time when the total flux is more than it for the closure and abandonment of coastal landfill sites | Repairing the steel-made side impervious walls on sea-side only |
Plan-4 | Repairing the steel-made side impervious walls on the both sides (sea side and landfill site side) | ||
Plan-5 | Hydraulic conductivity | Point of time when the hydraulic conductivity is more than it for the technical guidelines of impervious walls (1.0 × 10−6 cm/sec) | Repairing the steel-made side impervious walls on sea-side only |
Plan-6 | Repairing the steel-made side impervious walls on the both sides (sea side and landfill site side) |
In the case where a repair method is not applied, the result indicating the relationship between the concentration and total flux is assumed to be the “base plan”, and the time when the established standard is exceeded in each judgment index in this plan is shown in
In each repair plan, the transition of the standard exceedance probability for a given concentration of toxic leakage is presented in
Point of time over the standard | Elapsed time [years] | ||
---|---|---|---|
μ − σ | μ | μ + σ | |
Concentration | 11 | 16 | 24 |
Total flux | 15 | 23 | 44 |
Coefficient permeability | 9 | 22 | 52 |
repair is not confirmed as no difference can be seen after implementing plans 2 and 4. After 30 years, plans 1 and 2 could suppress the standard exceedance probability the most. Thus, the concentration of toxic leakage should be adopted as the judgment index for repair. When the side impervious wall on both sides is repaired, the leakage risk can be decreased using one of the repair methods.
In each repair strategy, the expected loss value and standard deviation for toxic leakage is calculated using the loss function. In addition, the results of the effect of risk reduction in each repair strategy is compared in
The concentration of toxic substances that leak into the sea area is the most suitable judgment index for repair. The repair strategies can suppress the decrease in water interception performance of the side impervious wall (for which the
judgment index is the toxic substance concentration in the surrounding water). Moreover, repairing both sides of the side impervious wall can decrease the toxic substance leakage risk.
Because the repair cost and the achieved effect vary according to the difference in the repairing method, the appropriate repair strategy can be determined using a net present value and the LCC. The repair cost is not considered because only the effect of risk reduction is considered in this study. Investment in the maintenance of social infrastructure in Japan is expected to decrease in the future; therefore, the repair strategy must be cost-effective. Cost effectiveness can calculate as follows [
The cost-effectiveness of each repair strategy can be defined in terms of the decrease in the leakage risk of the toxic substances. In other words, the monetary value of the reduction in the leakage risk is deducted from that of the leakage risk in the base plan. The repair cost is assumed to be the sum of the material cost of the additional water-swelling material required for repair (
The appropriate repair strategy varies according to the decision-making standard adopted in the maintenance strategy. In the maintenance of coastal landfill sites, only the sea-facing side of the side impervious wall need be repaired given the budgetary constraints. However, both sides must be repaired when reducing the leakage risk becomes the top priority. Therefore, an appropriate decision- making standard must be carefully adopted considering the environmental, societal, and financial factors in Japan.
The leakage of toxic substances from coastal landfill sites due to deterioration- induced decrease in the water interception performance of side impervious wall was quantitatively evaluated. In addition, asset management-based risk evaluation of the leakage of toxic substances with deterioration of steel side impervious
Effect of repairing NEL [Yen] | Repairing cost [Yen] | Cost-effectiveness | |
---|---|---|---|
Plan-1 | 6.77 × 108 | 2.20 × 106 | 3.08 × 103 |
Plan-2 | 5.52 × 108 | 2.20 × 106 | 2.51 × 103 |
Plan-3 | 6.06 × 108 | 2.20 × 106 | 2.75 × 103 |
Plan-4 | 7.60 × 108 | 4.40 × 106 | 1.73 × 103 |
Plan-5 | 5.92 × 108 | 4.40 × 106 | 1.35 × 103 |
Plan-6 | 7.22 × 108 | 4.40 × 106 | 1.64 × 103 |
walls and selection of an appropriate repair method was discussed. The results of this study can be summarized as follows:
1) Risk assessment considering the uncertainties in future coastal landfill sites was presented. The risk of the retained water leaking to the surroundings due to deterioration of impervious walls was considered the most serious environmental risk of coastal landfills. In the risk assessment, a loss function generally applied in earthquake risk analysis was adopted to determine the standard probability that the index exceeds the limited standard, the loss expectation (and standard deviation) of toxic substance leakage.
2) For social infrastructure, the exceedance probability of 10% after 50 years is considered acceptable; in this study, the risk of leakage was demonstrated to exceed this threshold after 15 years when using steel side double impervious walls. However, whether steel side double impervious walls can adequately contain toxic substances over time and with deterioration remain unclear.
3) An appropriate risk assessment-based maintenance strategy was proposed. The repair of the side impervious wall was used as the countermeasure, and the repair time and location that resulted in the largest reduction in the leakage risk were identified. The strategy of repairing when the concentration of the toxic substances leaking into the sea area exceeds that caused by the closure or abandonment of coastal landfill sites was shown to be the most effective. Moreover, the strategy of repairing only the sea-facing side impervious wall was found to be the most cost-effective.
This research was a part of the project titled “Development on technology for offshore waste final disposal”, funded by the Ministry of Oceans and Fisheries, Korea.
Inazumi, S., Sekitani, M., Chae, K.-S. and Shishido, K.-I. (2017) Evaluation of Maintenance Strategies Based on Leakage Risk Assessment on Side Impervious Walls at Coastal Landfill Sites. Materials Sciences and Applications, 8, 448-475. https://doi.org/10.4236/msa.2017.86031