Performance Of Landfill Research Articles

Field Water Balance of Landfill Final Covers

Landfill covers are critical to waste containment, yet field performance of specific cover designs has not been well documented and seldom been compared in side-by-side testing. A study was conducted to assess the ability of landfill final covers to control percolation into underlying waste. Conventional covers employing resistive barriers as well as alternative covers relying on water-storage principles were monitored in large (10 x 20 m), instrumented drainage lysimeters over a range of climates at 11 field sites in the United States. Surface runoff was a small fraction of the water balance (0-10%, 4% on average) and was nearly insensitive to the cover slope, cover design, or climate. Lateral drainage from internal drainage layers was also a small fraction of the water balance (0-5.0%, 2.0% on average). Average percolation rates for the conventional covers with composite barriers (geomembrane over fine soil) typically were less than 12 mm/yr (1.4% of precipitation) at humid locations and 1.5 mm/yr (0.4% of precipitation) at arid, semiarid, and subhumid locations. Average percolation rates for conventional covers with soil barriers in humid climates were between 52 and 195 mm/yr (6-17% of precipitation), probably due to preferential flow through defects in the soil barrier. Average percolation rates for alternative covers ranged between 33 and 160 mm/yr (6 and 18% of precipitation) in humid climates and generally less than 2.2 mm/yr (0.4% of precipitation) in arid, semiarid, and subhumid climates. One-half (five) of the alternative covers in arid, semiarid, and subhumid climates transmitted less than 0.1 mm of percolation, but two transmitted much more percolation (26.8 and 52 mm) than anticipated during design. The data collected support conclusions from other studies that detailed, site-specific design procedures are very important for successful performance of alternative landfill covers.

A probabilistic model and software tool for evaluating the long-term performance of landfill covers

A probabilistic model and software tool has been developed to assist in the selection, design, and monitoring of long-term covers for contaminated subsurface sites. The software platform contains multiple modules that can be used to simulate relevant features, events, and processes that include water flux through the cover, source-term release, vadose-zone transport, saturated-zone transport, gas transport, and exposure pathways. The component models are integrated into a probabilistic total-system performance-assessment model within a drag-and-drop software platform. Uncertainty and sensitivity analyses can be conducted that yield the following primary benefits: (1) quantification of uncertainty in the simulated performance metrics; (2) identification of parameters most important to performance; and (3) comparison of alternative designs to optimize cost and performance. A case study has been performed using the Monticello Mill Tailings Site in Utah to illustrate the important features and benefits of the modeling approach and software.

Performance of Solid Waste Landfills in Earthquakes

Interpretation and analysis of observational data on the performance of solid waste landfills during earthquakes is the most reliable source of information on the seismic response of solid waste landfills. The data from several major California earthquakes indicate that the general performance of landfills during earthquakes is from good to excellent. None of the landfills on which observational data is available experienced major earthquake-induced damage. Recorded strong ground motion data indicate that amplification of both peak and spectral accelerations can occur at the top of a landfill. This, combined with the fact that only a limited number of landfills with geosynthetic liners and no landfill with a geosynthetic cover have been subjected to strong ground motions, indicate that attention to detail is warranted in the design of modern, geosynthetic-lined and/or covered landfills in areas of high seismicity.

Identification of Dynamic Properties of OII Landfill

The performance of landfills during strong earthquake shaking is a matter of considerable concern and deserves to be studied more extensively. This paper investigates the dynamic properties of the OII landfill materials using strong motion recordings, available field measurements, and simplified physical models. Although the earthquakes recorded at the OII landfill generated shear strains as large as 0.08%, the landfill materials behaved as essentially a linear viscoelastic material, showing a negligible reduction in shear modulus with shear strain amplitude. The damping responsible for energy dissipation was found to depend on frequencies between 0.1 and 10 Hz. The physical origins of this frequency-dependent damping are not yet clearly understood. The results of this study are useful in analyzing the dynamic response of landfills and cap systems during small to moderate-size earthquakes. The present analysis is simplified because there were only two recording instruments at the OII landfill. It is recommended that researchers deploy more field instruments at this and other landfills to document their dynamic response during future earthquakes, and develop large-scale laboratory tests to determine landfill material properties under large static and dynamic strains.

Environmental hydraulics of sanitary landfills

This paper analyses sanitary landfills as biochemical reactors and particularly the significance of water balance and multi-phase flow in a landfill system. Field studies reveal a strong coupling between water content and landfill gas production. This study focuses on evaluation of field observations on water content, temperature, gas and leachate production in specially designed and operated landfills. Theoretical simulation of multiphase flow conditions - water and gas transport - has been carried out for different components of the landfill system. Top cover as barrier to gas exchange, 1-D heat transport and heat source distribution and water percolation reproducing mechanical dispersion due to presence of waste elements in the sanitary landfill are modelled to improve insight into the overall performance of sanitary landfills.

Simplified Seismic Design Procedure for Geosynthetic-Lined, Solid-Waste Landfills

This paper critically reviews seismic design practices in light of the observed performance of landfills during recent earthquakes. Developments in these areas are summarized as follows: earthquake ground motions, dynamic waste fill properties, dynamic responses of geomembranes and their interfaces, nonlinear dynamic response analysis, and seismic stability evaluation. A newly developed simplified seismic analysis procedure that requires the most critical factors be addressed during a seismic performance evaluation is presented. The underlying seismic analysis procedure has been validated against observed performance of landfills shaken by the 1989 Loma Prieta and 1994 Northridge, California earthquakes. The procedure is comprehensive in that it requires: (i) characterization of the design bedrock motions in terms of intensity, frequency content, and duration; (ii) estimation of the seismic loading at the base and cover of the landfill; (iii) e valuation of performance in terms of seismically induced permanent deformations; and (iv) appropriate engineering judgment.

Aspects of fluid flow through small flaws in membrane liners

Fluid flow through flaws (punctures, seams, or tears) in geomembranes used as flow barriers in the liners of landfills and surface impoundments is examined. Performance of a geomembrane deteriorates fairly rapidly with the first few flaws, much greater than their small area would suggest. As the membrane is penetrated with a greater number of flaws, the degradation asymptotes toward a proportionality with total flaw area. The rate of flow through the flawed membrane is frequently directly proportional to the permeability of the adjacent porous media. Geomembranes that are not used in conjunction with adjacent low-permeability porous materials are unlikely to give satisfactory performance in the event that flaws occur. A better understanding of design aspects that tend to minimize the impacts of flaws in geomembranes can lead to improved performance of landfills and surface impoundments.