Evaluation of cover soil properties of solid waste dumpsites in Colombo District, Sri Lanka

Abstract

Landfill cover soils have to serve multiple
purposes such as operational safety, environmental protection,
recultivation and integration of the sites into the landscape.
Cover soil properties must therefore be defined with respect to
the thickness, bulk density, air permeability and the available
field capacity. The primary objective of this study is to
examine the cover soil properties of three selected landfill sites
(dumpsites) in Sri Lanka in order to propose suitable cover soil
properties for similar applications in future dumpsites. Soil
samples were obtained from three landfill sites in and around
the city of Colombo. Laboratory tests to establish compaction
characteristics, air permeability, particle size distribution
and Atterberg limits were performed to assess the suitability
as landfill cover soils. The study showed that landfill covers
with well graded soils comply with the dry density and air
permeability values, as per the guidelines. In the absence
of proper gas venting facilities, it is essential to study the
permeability properties of the cover soil. All three landfill sites
tested need to be retrofitted with leachate and gas collecting
systems that meet the standards stipulated in the guidelines.