The American Society of Civil Engineers defines engineered landfill as-“A method of disposing of refuse on land without creating nuisance or hazard to public health or safety, by utilizing the principles of engineering to confine the refuse to the smallest practical area, to reduce it to the smallest practical volume and to cover it with a layer of earth at least at the conclusion of each days operation or at such more frequent interval as may be necessary.”

• If waste cannot be processed for recovery or as a source of energy and cannot be treated for discharge to the surface water or air, it must be disposed off on land. The landfill site should be so designed as to reduce environmental and health risks.
• The different methods of landfilling are as follows:

Trench Method:

1. This method is usually used in the case of flat terrain where the soil can be easily excavated.
2. A trench of about 2m depth and 5m width is used. The length of the trench depends upon the site conditions, and the number of trucks likely to arrive simultaneously at the site.
3. The size of the trench is so fixed that it is adequate to accommodate the quantity received during a day. The refuse trucks stand at the face of the trench and deposit their contents directly into it.
4. It is then compacted by appropriate equipment. The top of the trench is covered by a soil layer which should be at least 15cm thick.
5. When completed, such a landfill consists of a series of long narrow cells separated longitudinally by ridges or ribs of undisturbed ground. The top of the finished fill is raised above the original ground level.

Area Method:

• This method is mostly suited for irregular land where the ramp or trench methods cannot be conveniently used.
• The waste is deposited in natural depression as occurs in quarries, ravines and valleys. The waste is put in the natural depression and compacted.
• A 15 cm layer of earth is given on the top and compacted at the end of the day. The process is repeated till the depression is filled up and then the final soil cover is given.
• The earth cover has to be excavated from the borrow pits at the site itself or imported from elsewhere.