Landfill containment system

Table 1 summarizes typical values of acceptable calculated seismic displacement for non-geosynthetic components of landfill containment systems from a decoupled analysis, along with the anticipated duration for the interim and final repairs of these components. For the geosynthetic elements of waste containment systems, 150 mm of calculated displacement is generally considered to be indicative of no damage, and up to 3 m of displacement may be considered acceptable for geosynthetic elements in which... 

The landfill liner, cover, and hydraulic barrier all belong to the subsurface pollutant engineered containment system. The liner is designed at the bottom of a landfill to contain downward leachate. The cover is designed at the top of a landfill to prevent precipitation from infiltrating into the landfill. The hydraulic barrier, or cutoff walls, is a vertical compacted earthen system to contain horizontal flow of plume. The ultimate purpose of these barriers is to isolate contaminants from the environment and, therefore, to protect the soil and groundwater from pollution originating in the landfill or polluted site. 

Final cover systems are another important component of waste containment systems used at landfills. While liner systems are installed beneath the waste, final cover (or closure) systems are installed over the completed solid waste mass. For hazardous waste landfills, 40 CFR 264 requires that the landfill be closed with a final cover system that meets certain performance criteria, most notably, that they have a permeability less than or equal to the permeability of any bottom liner system or natural subsoils present. U.S. EPA guidance documents517 recommend that final cover systems for hazardous waste landfills consist of at least the following, from top to bottom ... 

Fail-safe Landfill The concept of the sustainable landfill is echoed in the philosphy of fail-safe landfill (Loxham, 1993). The fail-safe philosophy argues that whatever the containment system utilised, it will ultimately fail and/or institutional control will cease, and the contents within e.g., leachate, will be released to the environment. It therefore requires that any releases should be such that the risk posed to the environment is acceptable. For this to be the case, waste disposed to landfill must be pre-treated or degradation must be accelerated such that the hazardous nature of Ae waste and waste products are minimised. 

The principles of landfill practice were discussed in Chapter 2, and amongst the differing views on landfill best practice there seems to be at least one issue where there is a consensus of opinion. That is, whether for monofill or co-disposal, bioreactor or dry tomb, the use of a containment system is essential in the short term. However, according to local conditions and how "containment" is defined, a natural clay barrier may provide sufficient containment to satisfy the requirements of sustainable landfill. As discussed in Chapter 2, the dilute and attenuate principle (as an immediate management option rather than a long-term inevitability) can only be justified where a site-specific risk assessment has shown this to be feasible. Such a landfill may be appropriate for well-defined inert waste, where the expense associated with landfill lining could not be justified. This again... 

Although the USEPA also acknowledge the limitations of containment systems and weaknesses in the dry-tomb approach, the requirement for the "dry-tomb" approach to landfill management remains. 

An alternative bioreactor concept - the fermentationAeaching wet cell (F/L wet-cell) has been developed by Lee and Jones-Lee (1993). This concept also aims to effectively stabilise the waste and leach the soluble potentially polluting components. The design requires that the waste is shredded prior to emplacement to try to ensure contact of the liquid with all waste components. According to Lee and Jones-Lee (1993) who cite Ham (1975), this will also eliminate the need for daily cover, and has the potential to increase the capacity of landfill by about 20%. The other key feature of F/L wet-cell is the use of a clean water system beneath the clay of the composite liner to maintain movement of water up through the clay, thus preventing any leachate leakages to escape from the containment system. 

A landfill designed and operated in such a way that when containment systems faQ, or when there is loss of institutional control, the environmental risk is at an... 

The detailed design of the landfill depends very much on the criteria discussed in siting a landfill in the first place. Historically landfills have been operated as a dilute and disperse systems (Fig. 11.4) or as a containment system (Fig. 11.5). The majority of past landfills have been designed on the dilute and disperse principal by accident or default and a significant number continue in operation in the present time with many operating satisfactory. With the current EEC Directive on Landfill, a shift has taken place towards the principal of containment where both gas and liquid emissions from a landfill are controlled in such a manner that both... 

LandSim is particularly useful when comparing landfill designs, and allows optimization of the containment system at the design stage to permit maximum use of the degree of chemical containment afforded by the engineered and natural zones. 

For this reason, sodium bentonite might not be the most appropriate barrier material. Furthermore, other materials may be available more readily and might be more cost-effective to use. Therefore, much research has been directed at other low-permeability materials that might be used for active containment. Thornton et al. present results from a study of a high-attenua-tion liner material constructed from low-cost natural and industrial waste available in the UK. Laboratory column experiments were used to assess the performance of this and other potential liner materials to contain mobile organic and inorganic components by chemical means. Results of the experiments are discussed and linked to important landfill liner design issues. For example, additives could be included within the main liner material, or a separate liner could be placed beneath the main liner to act as a secondary chemical containment system. 

Equivalent linear analysis Geosynthetic Landfill Performance-based design Site response Solid waste Waste containment systems... 

Figure 1 illustrates the components of municipal solid waste (MSW) landfill waste containment systems. MSW landfills are by far the most common type of engineered waste containment system, followed (with respect to frequency of occurrence) by cover systems (caps) for uncontrolled dumps and hazardous waste sites and then by hazardous waste landfills. Caps and containment systems for hazardous waste landfills employ similar elements to MSW landfills. The performance of ancillary facilities at a waste disposal site subject to seismic loading, including leachate and gas treatment facilities, surface water control systems, access roadways, and landfill monitoring systems, is also an important consideration but will not be addressed herein. 

Seismic Design of Waste Containment Systems, Fig. 1 Containment system components for modem (/ ) and older (right) landfills (Kavazanjian et al. 1998)... 

Seismk Design of Waste Containment Systems, Fig. 2 Damage to landfills observed following the Northridge earthquake (a) cracking in soil cover on the... 

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