Applicability of Caliche (Gatch) as Liner/Cover in Arid Climate Landfills: Laboratory and Field Pad Testing of Permeability

Modernization of municipal solid waste (MSW) landfills needs basic environment protection furnished by base liner and cover systems. In an effort to help developed arid countries build safe MSW sites that are environmentally acceptable and cost effective, laboratory and field tests were conducted on the natural Kuwaiti calcareous sand, locally known as gatch, to study its applicability to liner and cover system. Laboratory test included permeability assessment using flexible wall permeability tests (ASTM D 5084). Permeability was assessed in the field by two-stage borehole permeability test (TSBs) (ASTM Z 2509Z). Laboratory results indicated that gatch sands are considered a low permeability soil when compacted at optimum moisture content and maximum dry density by the modified Proctor test. In the laboratory a permeability value as low as $4.0\times {10}^{-7}\mathrm{cm}/s$ was recorded. A field test program was conducted on both natural gatch deposits and compacted gatch pads. These field results suggest that in situ gatch deposits could be considered as a secondary barrier system beneath in the liner. Similarly, permeability values of compacted gatch were between $3.0\times {10}^{-5}$ and $17.0\times {10}^{-5}\mathrm{cm}/s$. Upon desiccation, permeabilities of compacted gatch decreased. On the other hand, drying and wetting cycles conducted on the test pads and in the lab have recorded increased permeability values.