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APPLICATIONS: importance of SUBSURFACE CONDITIONs for picking landfill sites

     There are several aspects that must be examined as regards underground characteristics of a given potential site.

     Because of the need for suitable cover and liner material, subsurface soil type characteristics are not to be trifled about.  Siting a landfill in the wrong place may translate into having to bring in cover soil from far away places.  Soil and subsurface characteristics are important as well because we would tend to look after "spontaneously good" (= naturally impervious) subsurface terrains such as clays or silts.  Underground matrices consisting of gravels or sands will not do.  Proper soil characteristics can play an important role in migration control.  Targeted site location soils will have to be appropriate to provide a firm foundation and construction involved, including roads and minimizing liner damage potentials.

     Distance to groundwater   will determine to a certain extent how deep we can go.  Subsurface formations and groundwater conditions will have an impact when designing leachate collection and lining systems.  Vertical and horizontal migration patterns may translation into leachate migration to undesirable places.

LANDFILL LEACHATE and how to deal with it

     Based on a number of treatability assessments conducted, landfill leachates are very difficult to treat.  They contain significant amounts of nonbiodegradable or very slowly biodegradable organics and often contain substantial amounts of color.  Heavy metals usually are a minor problem since they will be absorbed by the biomass.  Nitrogen levels usually are high so that ammonia released or there will be a demand for oxygen to satisfy nitrification.  High O&G probably.  It is recommended that treatability tests be conducted so that the designer will know exactly what removal efficiencies can be achieved.

BASIC LANDFILL DESIGN PROCESS

     The complex procedure for designing a given landfill can be divided in about five major design steps.

1.  Establishment of goals and design data including determination of solid waste quantities and characteristics, both actual and projected for such things as type of waste to be accepted/rejected; areas to be served; planned life, user profiles; tip fee schedules, population and future growth data, current and projected solid waste generation rates figuring in any commercial/industrial development and assessing effect of recycle and recovery programs.

2  Compilation of information for [the various] potential sites including but not necessarily limited to:

• conducting topographic and boundary surveys
• elaborating base maps including major features, i.e. property boundaries, water bodies, roads and buildings, slopes, land use
• hydrological and geological information including soil data, e.g. depth, moisture, density; bedrock data, e.g. depth, fractures, outcrops; and groundwater data, .e.g. depth, gradients, quality
• meteorological/climate data including precipitation and evaporation rates, temperature profiles, winds
• applicable regulations and standards, such as [road] loading limits, cover frequency, hauling distance, surrounding water bodies, nearby/existing airports, groundwater standards, building codes    

3.  Sizing of filling area which will include 

• landfill method, e.g. area method vs trench method
• cell specifications to include W*L*D and all thicknesses, i.e. liners, interim soil cover, final cover
• operational data such as soil use, cover method, supplemental soil needs (import), equipment and personnel requirements

4. Specific features such as

• leachate handling
• gas recovery apparatus
• surface water controls
• working areas and access roads
• special waste type management
• structures, utilities, lighting, ventilation, fencing
• monitoring [well] systems
• interplay with recover/recycle operations
• other, e.g. wash racks, landscaping

5.  Package preparation, i.e. plans, diagrams and documents of all sorts such as

• fill areas
• contour maps including excavation plans, fill sequence, completed cell plans plus planned controls, i.e. fire, odor, noise, vector, junk
• calculation of storage capacity (volume), soil volume needs, service life
• finalized site plans illustrating the various areas, e.g. fill, working; control systems; access
• elevation plans and different stage and phase cross sections
• several other documents presenting things like construction details, proposed land use, cost estimates, design report, EIA preparation, application and permit securing; operator's manual