Field-based assessment of the design of lysimeters for landfill final cover seepage control

ABSTRACT

Lysimeters are considered the most appropriate instrument for assessing percolations rates through landfill final covers. Their design, however, must take into consideration the unsaturated nature of water seepage, otherwise they may act as a sink or cause flow avoidance. The aim of this study was to investigate whether using a simple approach to lysimeter design produces reliable seepage control data. Two different design methods were compared using a three-year field database of suction and seepage data collected from large-scale lysimeters installed at the St-Nicephore landfill in Canada. The first, or control, whose side walls were as high as the thickness of the cover material, was inspired from lysimeters installed during the Alternative Cover Assessment Program (ACAP; USA). The second lysimeter was designed based on the proposed simple design methodology, which focuses on the unsaturated flow and hydraulic properties of the materials to determine the optimal wall height. Analysis of the database did not show any indication of significant preferential flow, or alteration of the flow regime by the second lysimeter, which collected as much percolation as the control one (less than 5% difference). The linear method has not been tested for extreme climatic conditions and the wall heights calculated using this method may be very high when designed for very fine-grained soil covers.

Acknowledgements

The authors sincerely acknowledge the invaluable help of several undergraduate and graduate students, during characterization tests in the laboratory, construction, equipment installation and monitoring. We also wish to thank the WM Quebec Inc. personnel at the St-Nicephore landfill site for their help.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within this paper.

Additional information

Notes on contributors

Thierry Kahale

Thierry Kahale has a BSc. in Civil Engineering from the Universidade Federal do Parana (UFPR) Brazil, (2012). He completed his Ph.D. in civil engineering, at the Université de Sherbrooke, Quebec, Canada in 2022. Thierry has over six years of experience as a geotechnical engineer and currently works as a manager in the Mining Waste department at WSP Group.

Ousmane Ouédraogo

Ousmane Ouédraogo has a BSc. in Civil Engineering from Ecole Nationale de Travaux Publics, Burkina Faso (2015). He completed his master's degree in 2017 from École Polytechnique de Thiès (2017), Senegal. He is currently a PhD. student at the Université de Sherbrooke, Quebec, Canada.

Mauro Duarte Neto

Mauro Duarte Neto received his BSc. in Civil Engineering from the Escola Politecnica of the Federal University of Rio de Janeiro (UFRJ), Brazil (2013). He completed his Master's degree in 2019 at the Université de Sherbrooke, Quebec, Canada. He has thirteen years experience as a project manager in civil engineering and infrastructure projects. He is currently project leader in environmental management and landfill implementation for WSP Group.

Virginie Simard

Virginie Simard received her BSc. in Civil Engineering from Université de Sherbrooke, Québec, Canada (2017). She completed her master's degree in 2019 from the same institution. Virginie currently holds the position of engineering project manager for the municipality of Saint-Jérôme Quebec.

Alexandre R. Cabral

Alexandre R. Cabral, P.Eng, received his Bsc. from PUC-Rio, Brazil, in 1981, his M.Sc. at École Polytechnique de Montreal, in 1988, and his Ph.D. at McGill University, Quebec, Canada, in 1992. He started his academic career at Université de Sherbrooke in 1994. His main research interests are methane oxidation biosystems for the reduction of greenhouse gas emissions, unsaturated flow through porous media, and classical geotechnical issues, such as soil compaction. He is currently leading research projects in all these areas. He has co-authored papers published in geotechnical, environmental engineering and science-oriented journals.