Applicability of Local Soils as Base Liner Materials to Construct Sanitary Landfill

Abstract

This thesis represents the findings of application of local soils as base liner materials in the construction of Pilot Scale Sanitary Landfill (PSSL) at Rajbandh, Khulna, the ultimate disposal site (UDS) of Khulna City Corporation (KCC). The base liner of pilot scale sanitary landfill has been studied in situ condition during and post construction phases. The sub-soil investigation was carried out at the PSSL site to identify the soil strata, physical and engineering properties. Boring to a depth of 17m revealed that the gray clay minerals with organic forms to a depth of 1 .5m followed by silty clay having clay minerals content ranges from 23 to 30% and hydraulic conductivity varies from 2.45x10to6 to 2.5x10 to-8 cm/sec at different molding water content. Swelling clay minerals are present in varying the amount of 0 to 11% of the composition. The characterization shows that local soils at UDS of Rajbandh are suitable as a compacted clay liner for the construction of sanitary landfill, which has been verified in this study in field conditions. This study describes the process employed for the construction of PSSL. A very simple but technically compatible design is considered here to use local building materials and to avoid any imported or expensive materials such as any kind of geosynthetics. The available indigenous approach mostly manual labor intensive was employed to complete the construction of landfill. This field experience described in the study, which will help in establishing the sanitary landfill construction standard for Bangladesh based on the local conditions, socio-economic settings and technological capabilities. The mineralogical of the top clay layer also indented through standard laboratory test to see the potentiality as clay barrier to be used in the PSSL. A team consisting Asian and European design the PSSL based on local conditions, availability of natural barrier and construction materials, technical needs and the expert's experience. In the construction phases, emphasis was given on the best use of local building material, huge potential of manual labor force and the technical requirements. The performance of base liner has been measured by collecting the percolating water on areas from 2500 m2 of compacted clay liner. The performance of compacted clay liners, however, decreased severely within one year due to desiccation and shrinkage. The maximum percolation rates have increased from 36 x 10to-3 to 46.6x10 to -3 m 3 /day. 400mm of compacted clay liner (CCL) has been tested for one year. The CCL desiccated during the first dry summer of the study. High percolation rates through the CCL were measured during the monsoon. Wetting of the CCL did not significantly reduce the percolation rates. The laboratory test result of leachate from detection & collection system shows that the base liner has protected the migration of contaminant significantly. It also prevents the percolation of leachate as the major portion of generated leachate has been received through the collection system. The water tested in ground water monitoring well indicates that CCL works appreciably to prevent the migration of leachate from the landfill cell. Finally, it can be concluded that the CCL is constructed in the base liner using local clay and the construction techniques works with high degree of satisfaction.