Effects of Hydraulic Gradient and Permeant on the Hydraulic Conductivity of a Tropical Residual Soil for Landfill Liners T. V. B. Zanón 1 , D. Lunardi 2 , and M. E.G. Boscov 3 1 M.Sc., University of Sao Paulo, PO Box 8084, 05508-900, Sao Paulo, SP, Brazil; PH +55 11 97681 8055; email: thiago.villas@gmail.com 2 Graduate Student, Environmental Engineering, University of Sao Paulo, PO Box 8084, 05508-900, Sao Paulo, SP; PH ++55 11 97260 8989; email: daniel.lunardi@usp.br 3 Professor, Department of Structural and Geotechnical Engineering, University of Sao Paulo, PO Box 8084, 05508-900, Sao Paulo, SP, Brazil, PH ++55 11 99137 9203, email: meboscov@usp.br ABSTRACT For the two last decades, new municipal solid waste (MSW) landfills have been built and operated in Brazil in consonance with international criteria. Some old dumpsites have been remediated and adapted to environmental regulations. However, still about 42% of MSW generated in Brazil is inadequately disposed of in dumpsites or landfills with precarious environmental protection. In 2010, a Federal Law has instituted the eradication of all inadequate disposal sites, whereas in the same year technical standard for low volume sanitary landfills has flexibilized the need for bottom liners depending on hydrological and climatic local conditions. This paper presents the geo-environmental characterization of a lateritic clayey soil which represents a group of soils of significant occurrence in some Brazilian states, sampled in a sanitary landfill which recently underwent a reclamation process. Permeability tests were carried out with disturbed and undisturbed samples, with water and sanitary landfill leachate. Hydraulic conductivity of the natural soil, circa 1x10 -6 m/s, decreased to about 5x10 -8 m/s by compaction at standard proctor energy, and remained constant or decreased slightly by leachate seepage. On the other hand, leachate seepage through compacted soil caused severe pore clogging under hydraulic gradients representative of field conditions. This may impair the utilization of column tests to evaluate transport parameters of pollutants in real MSW leachate. Keywords: sanitary landfill, tropical soil, hydraulic conductivity, leachate, compacted soil 1 INTRODUCTION Through the last two decades, many dumpsites in Brazil were closed or reclaimed for the implementation of proper sanitary landfills. However, 60% of 5,565 Brazilian municipalities still dispose of municipal solid waste (MSW) in dumpsites or landfills with precarious environmental protection, 98% of which located in small towns (ABRELPE 2013). A Federal Law from 2010 established that until 2014 all dumpsites should be eradicated and henceforth MSW should be adequately disposed of (BRASIL 2010). In spite of the fact that this goal was not reached and a term extension is in negotiation, it is nevertheless clear that in the next years many sanitary landfills will have to be built. Requirements for bottom liners of sanitary landfills from environmental agencies in Brazil are usually based on those of the United States Environmental Protection Agency (USEPA 1993): a impermeable barrier, consisting of a compacted clay layer with a thickness of 0.60 m and a maximum hydraulic conductivity of 10 -9 m/s covered by a 0.002-m thick HDPE (high density polyethylene) geo-membrane, overlain by a granular drainage layer. For small towns, however, trench landfills without bottom liners are still accepted, and under certain hydro-geological and climatic conditions, even area fills may be dispensed of this protection (ABNT 2010). These flexible requirements are motivated by the lack of financial, technical and human resources in small municipalities, but systematic studies must be encouraged to support decisions on the minimum necessary measures for environmental protection. This paper describes an investigation on the hydraulic conductivity to water and MSW leachate of a lateritic clayey sand, representing a group of soils of significant occurrence in the state of Sao Paulo, ISBN 978-1-922107-23-7 © 2014 Engineers Australia 1524 Table of Contents for this manuscript