Landfill and Settlement The Basics Discussed

The final (post-settlement) levels and contours of a landfill must be indicated when drawing up a site restoration plan. In order to achieve these it is necessary to anticipate the amount of settlement that will occur and to ensure that this takes place as evenly as possible. The rate and degree of settlement occurring at a landfill will always be site specific depending on the site itself, landfill practice, and the effects of mechanical and biochemical processes.

A Landfill Compactor Machines Use Its Compactor Wheels which have Steel Cutting Surfaces to crush and cut the waste before squashing it into the landfill



Current landfill site practice has eveloved in response to the requirements of the Waste Regulations (UK), where the driving force is to minimise leachate generation.

Whenever a part of the operational cell is completed to restoration levels it is likely to be capped to prevent further ingress of rain water.

So, under these circumstances significant settlement can then be expected, no matter how well the waste is compacted by the action of the site "compactor vehicles" (wheeled or sometimes tracked front-end shovels - often called "buldozers" by the public).

During capping more rstoration material weight will be added. This will result in continued, physical compression compaction throughout the waste.

The production of gas will mean in very approximate terms a net mass loss of possibly 18% in total waste mass assuming 150m3 of landfill gas is in time extracted from each tonne of waste at 1.15kg/m3.

Removal of leachate from lower levels of waste may also cause further settlement which is probably due to the pore water pressures being reduced.

Settlement is predictable and must be catered for in the design of the gas abstraction system.

Determination of settlement rates and possible leachate levels is particularly pertinent to new sites and are important design parameters for the landfill gas Engineer to determine before he starts his system design.

If you need your landfill modelled for settlement, and settlement prediction provided, this is a service we provide regularly through our associated consultants.
Steve Evans has provided more leading information on Landfill Settlement issuesat his blog. A full version of this article is available at Settlement at Landfills.