Landfill reclamation is the process of transforming a full landfill from wasteland to woodland by successfully turning garbage into resilient landscapes.
Landfill sites are large expanses of derelict land found near cities that in some cases have had a previous life as a mine or quarry and now act as a large garbage receptacle. The past few decades has seen an increased interest in reclaiming these areas for recreational purposes, either as large parks or woodlands, because of the size or price of the land and for the simple fact that they are too unstable and toxic to allow for any other type of activity.
These sites are most often situated in densely populated areas that would benefit significantly from having an upgrade and a return to a natural environment such as a park or recreational facilities can provide. Here is a look at some of the major issues that must be dealt with in any landfill reclamation project.
Subsidence is the issue of how much the ground will settle when the garbage begins to compact and shift. It can be very severe, from 5 to 20% of landfill depth over the course of 20 to 30 years causing significant damage to any built environment such as foundations, irrigation and gas pipes.
LEACHATE AND WATER CONTAMINATION
Leachate is the liquid substance that is produced when rainwater percolates through the solid waste of the landfill, is contaminated in the process, and may then result in hazardous substances entering groundwater. To prevent any infiltration of water, sites are capped by creating layers of compacted clay topped with an erosion cover layer that is capable of sustaining vegetation.
Many factors may cause a flaw in the cap that would then allow leaching to take place such as settlement or dryness cracking the cap or tree roots piercing through the cap.
Waterlogging as well as the release of toxic gases (methane and carbon dioxide) produced by degrading waste is problematic because it causes conditions in the soil that could be devastating for many plants and trees. Firstly a layer of drainage material should be laid down, then subsoil should be placed on top, followed by topsoil to allow for a vegetative cover. Topsoil is a precious component of the environment that, within a few millimeters of soil, contains much of the growth capacity that sustains life and as such, is of vital importance to human existence.
Planting up a site has many benefits. Vegetation ensures an erosion defense by protecting the cap from wind as well as to provide slope stabilization where a landfill has been constructed above ground and materials have been piled high. A vegetative cover atop the cap slows down absorption rates of water into the soil which is particularly advantageous seeing as how the soil layer is actually quite shallow and that the clayey material of the cap generally encourages water logging. It is the first defense for storm water management.
Another way that some landfills have adopted to deal with storm water is to have a wetland collection pond to deal with water run-off as well as create a wildlife habitat. This pond can double as a water treatment pond if ever groundwater was found to be contaminated, by pumping it up to the surface and then cleaning it through the use of certain plants.
In our day and age, sustainability must include accountability. The move to clean up and reclaim landfills and brownfield sites is fast emerging as a response to that.