Optimal ranges of soil index properties for diesel containment using compacted barriers

Abstract

Results of laboratory and field permeability tests performed in order to specify optimal ranges of soil index properties for the containment of organic liquids are presented. Liners for waste containment are often constructed with the use of fine-grained, high-plasticity natural soils, which normally present low hydraulic conductivity and are capable of attenuating inorganic soluble chemical species. However, because of the low polarity of most non-aqueous phase fluids (NAPLs), the effectiveness of fine-gained soils for NAPL containment is controversial. Several permeability tests were performed using soils with different characteristics and compaction energies. As expected, tests performed using diesel (low dielectric constant) presented higher permeability coefficients (k) than water in fine-grained soils. Concerning the diesel tests, soils compacted in the normal Proctor energy were unable to achieve values of k ≤ 1 × 10–8 m/s recommended for petroleum derivative storage areas. Soils compacted in the modified Proctor energy within specific ranges of index properties were able to fulfil regulatory requirements. Index ranges were defined towards long-term liner performance and were used to construct experimental landfills. Field and laboratory permeability tests were performed in the landfills, validating the applicability of the proposed ranges, although some adjustments are applied for better field performance.