Sanitary Landfill design and Siting Criteria

*** Compilado por RESOL Engenharia LTDA ***

March 1996 TRANSPORTATION, WATER AND URBAN DEVELOPMENT DEPARTMENT, WORLD BANK Urban No. UE-12



SANITARY LANDFILL DESIGN AND SITING CRITERIA

Sandra Cointreau-Levine

For two decades, solid waste components in World Bank projects have focused on collection of solid wastes, with equipment provided to upgrade operations at existing open dumps. In the past several years, the private sector is increasingly being involved in the collection of solid waste and World Bank projects are beginning to place greater priority on implementation of new sanitary landfills. The following guidance provides an examination of some of the issues which need to be addressed in landfill siting and design.

Sanitary landfill is the most cost-effective system of solid waste disposal for most urban areas in developing countries. Composting of solid waste costs 2-3 times more than sanitary landfill, and incineration costs 5-10 times more.

A sanitary landfill is a contained and engineered bioreactor and attenuation structure, designed to encourage anaerobic biodegradation and consolidation of compacted refuse materials within confining layers of compacted soil. At a proper sanitary landfill, there are no nuisance impacts of constant burning, smoke, flies, windblown litter, and unsightly rubbish heaps.

Refuse in a proper sanitary landfill is not directly exposed to rainfall, surface runoff or groundwater. Leachate generation is derived only from a limited quantity of infiltration which reaches the waste deposit and captures the byproducts of waste biodegradation. While little leachate is generated in a sanitary landfill compared to an open dump, leachate concentrations are much higher-organics are higher by a factor of more than 10-and thus needs to be properly treated.

Sanitary landfills located in arid areas, where there is minimal potential for leachate generation, may have more relaxed design requirements than those located in wet areas. Similarly, sanitary landfills located on coastal lands underlain by naturally saline and unpotable groundwater may have more relaxed design requirements than those in inland areas overlying potentially usable groundwater regimes. In these areas of lower impact potential, impermeable lining of the landfill may be unnecessary. Instead, measures to enhance natural attenuation by soil's adsorption, precipitation, filtration, and ion exchange capacities need to be considered.

Sanitary landfill design needs to provide for daily cover of fresh refuse, route runoff away from waste cells, incorporate mitigative measures to manage leachate and gas produced within the landfill cells, provide for a final soil and vegetative cover, and establish an environmental monitoring system of upgradient and downgradient groundwater monitoring wells and surface water sampling locations. Typically the daily cover material is soil; however, tarps or inert materials (i.e., construction debris or compost residuals) could be used.

Since the sanitary landfill is the most important control node of the refuse collection system, a gate-house for record-keeping operations and a weighbridge are recommended. A weighbridge generally costs no more to purchase than one refuse collection truck, and assures the productivity of the entire collection fleet.

Minimizing Leachate Generation. A sanitary landfill is a step by step construction activity involving daily layering, compacting, and soil covering of refuse into cells. The space wherein the refuse would be placed should not be subject to seasonally high groundwater levels or to periodic flooding. The site preparation and landfilling operation must be designed to minimize contact of surface runoff and percolating rainwater with the refuse. This requires di

Aterro Sanitário, Português, Trabalhos Técnicos

Sandra Cointreau-Levine

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