4.3.1.1. Environmental criteria 4.3.1.1.1. Land
slope
(Lin & Kao, 2005) have suggested that the appropriate
slope for constructing a landfill is about 8-12% because too steep of a slope
would make it difficult to construct and maintain while too flat of a slope
would affect the runoff drainage. Slopes above 12% created high runoff rates
for precipitation. With higher runoff rate and decreased infiltration,
contaminants are able to travel greater distances from the containment area.
4.3.1.1.2. Proximity to wells and Forest
A landfill must not be located near any surface streams,
lakes, rivers, wells, or wetlands. Proximity to wells was an important
criterion to accessing the landfill site. Landfills create noxious gases and
leachate that make them unsuitable to be in proximity to water wells (Dorhofer
& Siebert, 1996). For this reason, a 300-m buffer would be placed using the
function in GIS software, which will be used to generate the buffer around all
wells and forests.
4.3.1.2. Social- economic criteria
4.3.1.2.1. Airports
Landfill sites attract variety of birds to be accumulated
around. This issue may interfere with the operation of airplanes. So it is
essential to consider suitable distance from landfill site according to airport
and airplane types (Daneshvar, 2004). By considering this criterion as a
constraint, for safety matters, 3 kilometer buffer around airport was omitted
from the next investigation.
4.3.1.2.2. Roads network
Landfill location must be close to roads network in order to
facilitate transportation and consequently to reduce relative costs. However,
aesthetically and logically a buffer of 100 meter has been considered in this
study. In other words, direct relationship between distance from roads and land
suitability is started from the 100 meter distance of roads.
4.3.1.2.3. Schools, Hospitals and Markets
By considering this as a constraint, a buffer of 01 Km will be
reserved to Primary and Secondary schools, health centers and District
hospitals, and markets (REMA, 2010).
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4.3.2. Landfill site determination
The site selection analysis involves three steps: preliminary
analysis, multi-criteria evaluation, and identification of the most suitable
site. The preliminary analysis stage involves creating a study area map to
input the data layers, then creating permissible area map for landfill sites in
Rusizi town.
The second step involves performing GIS overlaying, which is
conducted by combining the non restricted area map and slope analysis map in
order to get the suitable landfill sites in Rusizi town that would be located
in the intersection of non restricted area and suitable slope. The final step
relates the finding of suitable sites using the information in advanced GIS and
REMA regulations regarding landfill site's size.
Non restricted area map, Slope analysis map, Potential
landfill sites in Rusizi town, Potential landfill sites in Mururu Sector,
Potential landfill sites in Gihundwe Sector and General Suitability maps were
created and produced.
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