Environmental Factors Affecting Choice of Disposal Sites
Having identified land as the main disposal medium in waste management identification of the suitability of potential landfill sites requires a comprehensive assessment of site conditions and potential impacts on the environment.
Several factors affect the choice of disposal sites especially for hazardous and toxic waste. This is to ensure that proper care is taken to mitigate or minimize the occurrence of adverse effects to man and the ecosystem within the sites.
These factors includes:
- Soil condition
- Climate (including air quality and odour modelling)
- Flora and fauna
Suitable geology is important to ensure containment of leachate in the long term, or in the event of engineered containment systems failing.
Geology should be assessed with regards to the movement of leachate and landfill gas.
Landform in the vicinity of disposal sites will influence drainage, potential ground water problems, soil erosion risk, access, site visibility and protection from prevailing winds.
A suitable site will have sufficient grade to provide drainage of surface runoff and adequate level areas to enable excavation of trenches and associated earthworks and the construction of service facilities. Sites with slopes exceeding because of soil erosion risk.
Careful consideration needs to be given to the landforms in the vicinity of the disposal site as they may influence:
The type of disposal method that can be utilized;
The suitability of the site for construction of service facilities;
Surface water drainage management;
Soil erosion risk;
Access to the site;
Ability to screen the site from view; and
The impact of winds on the site.
3. Soil condition
Soil structure should be suitable for the excavation of landfill cells or trenches and the construction of drainage works and should also be of sufficiently low permeability to slow the passage of leachates from the site.
Sites in clay-rich environments are preferable, as their low permeability will allow more time for natural attenuation of leachates to occur.
In establishing the suitability of a site, several test pits should be dug to determine the ease of excavation of the in-situ material and the suitability of soil types.
A suitable hydrogeological location is important to protect groundwater resources and understand the likely fate and rate of discharge of contaminants which may enter groundwater.
Landfills must not be located in the following areas: areas overlying drinking water aquifers; and/or areas where, after taking into account specific design proposals, there could be a risk of causing unacceptable deterioration of the groundwater quality in the locality.
The purpose of a hydrogeological assessment is to determine the relationship between the landfill and surrounding hydrogeology in order to ascertain the potential risk the landfill facility will have on the environment.
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The pollution of surface water by leachate is one of the principal concerns in relation to landfill location. If landfills are located in close proximity to waterways, there is an increased risk of water pollution through leachates.
Leachates are generated by water passing through waste materials in landfills and becoming exposed to and mobilizing a range of contaminants. The potential impact of water pollution is greater in waterways that are used for drinking water or aquaculture.
Climate (including air quality and odour modelling): Consideration should be given to the local climatic conditions when siting a waste disposal facility. The heavy rainfall situations which can occur in the issues if landfills are not sited and designed in an appropriate manner.
Hot, dry windy conditions can cause dust and windblown waste issues. Landfills should be located in an area which facilitates the management of landfill issues.
6. Flora and fauna
The development of landfills may impact on the flora and fauna of the local area. The potential impacts on flora and fauna are:
Clearing of vegetation;
Loss of habitat and displacement of fauna;
Loss of biodiversity by impacts on rare or endangered flora and fauna;
Potential for spreading plant diseases and noxious weeds;
Litter from the landfill detrimentally impacting on flora and fauna;
Contamination of sensitive ecosystems, such as wetlands, by leachate;
Creation of new habitats for scavenger and predatory species;
Alteration of water courses.
Local infrastructure must be able to sustain the operation of a landfill.
Landfilling requires the transportation of waste. As a result, the capacity of the road network to cope safely with a minimum of disturbance to the local community and increased traffic load should be examined.
The preferred transportation route should minimize the transport of waste through residential and other sensitive areas. This consideration may influence the placement of the entrance to the landfill.
A transportation study may reveal the need for additional road infrastructure, such as highway interchanges, turning lanes or signals.
The availability of services such as reticulated water, sewerage and power will influence the facilities provided for staff at the landfill and, perhaps, indicate a need to provide additional services, namely, water storage for fire-fighting purposes.
A landfill facility must have all weather access. Access roads should be located to minimize erosion and the alteration of drainage systems.
This road should be designed to safely accommodate the anticipated volume of vehicular traffic and consist of two lanes of sufficient width and strength to carry the delivery vehicles.
The access roads intersection with the existing public road should be carefully designed to reflect traffic volumes and safety requirements.
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