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Longueuil, Canada

Vachon B.L.,Groupe Qualitas inc. | Vachon B.L.,Universite de Sherbrooke | Abdolahzadeh A.M.,Universite de Sherbrooke | Abdolahzadeh A.M.,AECOM Technology Corporation | Cabral A.R.,Universite de Sherbrooke
Canadian Geotechnical Journal | Year: 2015

Covers with capillary barrier effect (CCBE) have already been proposed to meet regulatory requirements for landfill final covers. Modeling of CCBE can be a relatively complex and time-consuming task. Simpler, albeit conservative, design tools— such as steady state numerical analyses—can, in certain cases, be justified and have a positive impact in practice. In this study, numerical simulations were performed of the experimental CCBE constructed on the Saint-Tite-des-Caps landfill (Quebec). The CCBE consists of a capillary barrier, composed of sand and gravel, on top of which a layer of deinking by-products (DBP) was installed as a protective layer (also to control seepage). The addition of a protective layer over the infiltration control layer (such as a capillary barrier) is required in most jurisdictions. In many European countries, such as Germany and the Netherlands, a thick “recultivation” layer is required. The results of numerical simulations were compared with the in situ behaviour of the Saint-Tite CCBE as well as with analytical solutions. The effectiveness of the capillary barrier was assessed by quantifying the diversion length (DL), which reflects the lateral drainage capacity of the CCBE, i.e., the capacity to drain water laterally. Collection of the water that has drained laterally prevents seepage into the waste mass. This study shows that when the seepage rate reaching the top layer of the capillary barrier is controlled, it is possible to predict the worst-case scenario in terms of seepage (and therefore predict the shortest DL) using steady state numerical simulations. These simpler-to-perform numerical simulations could be adopted in practice, at least in a pre-feasibility study for cases with a similar profile as the one at the Saint-Tite-des-Caps experimental CCBE. © 2015, National Research Council of Canada. All rights reserved.

Boudreault J.-P.,Ecole de Technologie Superieure of Montreal | Dube J.-S.,Ecole de Technologie Superieure of Montreal | Chouteau M.,Ecole Polytechnique de Montreal | Winiarski T.,National School of Public Civil Engineering | Hardy E.,Groupe Qualitas inc.
Engineering Geology | Year: 2010

This study presents the use of geophysical methods as a preliminary step in the characterization of urban fills, namely for the assessment of the spatial variability of their internal structure. The test site is located near downtown Montréal (Québec, Canada) and had a surface area of 1600m2. A heterogeneous fill was encountered on the entire site and mainly consisted of a matrix of remolded natural soil material mixed with various debris (e.g. concrete, brick, metal), as well as industrial and domestic wastes (e.g. ash, slag, clinker, coal). Old foundation walls were suspected to be still in place in the fill at the location of previous buildings. The results obtained show that a combination of geophysical methods sensitive to different physical properties of the subsurface is necessary to confirm the presence of heterogeneities, their nature, and assess their lateral and vertical extent in urban fills. To validate the nature of the anomalies detected during the geophysical survey, trench excavation and sampling were performed after completion of the geophysical survey. By cross-analyzing the horizontal imaging methods and vertical imaging methods, it was possible to delineate zones of distinctive heterogeneity and establish the contact between the fill and the natural soil material. Thus, as opposed to conventional characterization techniques, which rely on trench excavation or borehole drilling and only provide a localized estimation of fill properties, geophysical methods helped in imaging the external and internal geometry of a fill in a continuous manner. © 2010 Elsevier B.V.

Dube J.-S.,Ecole de Technologie Superieure of Montreal | Boudreault J.-P.,Groupe Qualitas inc.
Ground Water Monitoring and Remediation | Year: 2011

The dissolution of gases, such as oxygen, in groundwater is a means to provide electron acceptors required for the biological degradation of organic contaminants in aquifers. The use of polymeric emitters for passive gas diffusion in groundwater significantly increases the efficiency of oxygen transfer to the groundwater compared to conventional sparging. A critical parameter for the design of polymeric emitters is the diffusion coefficient (D) of the polymer tubing used to construct the emitters. Wilson and Mackay (1995) proposed a mathematical model (WM model) for the analysis of laboratory passive diffusion experiments aimed at characterizing D. Their analytical solution is obtained in Laplace space and its inversion requires the use of a numerical approximation technique. This article proposes an alternative to the WM model by simplifying it as a dimensionless ordinary differential equation (ODE) which is solved using simple integration. The validity of the dimensionless solution is discussed and the latter plotted into charts to provide easy-to-use analytical tools applicable to gas or solute diffusion in groundwater. © 2011, The Author(s). Ground Water Monitoring & Remediation © 2011, National Ground Water Association.

Boudreault J.-P.,Ecole de Technologie Superieure of Montreal | Boudreault J.-P.,Groupe Qualitas inc. | Dube J.-S.,Ecole de Technologie Superieure of Montreal | Sona M.,Ecole de Technologie Superieure of Montreal | Hardy E.,Groupe Qualitas inc.
Science of the Total Environment | Year: 2012

Soil sampling is a critical step in environmental site assessment studies. The representativeness of soil samples has a direct influence on financial, liability, environmental and public health issues associated with the outcome of remediation activities. Representativeness must be quantified for assessing and designing soil sampling procedures. Gy's Sampling Theory and Practice (STP) was used to analyze the reproducibility of two soil sampling procedures, namely a procedure based on grab sampling (GSP) and an alternative procedure (ASP) developed from STP principles. Sampling reproducibility, a component of sampling representativeness, was determined by theoretical calculations and experimental measurement of relative variances in trace metals concentrations at each stage of both sampling procedures. The ASP significantly increased the reproducibility of soil sampling compared to the GSP. Larger relative variances occurred during field sampling for the ASP and during laboratory sampling for the GSP. They were due to subsample mass reduction without control over particle size. Relative theoretical and experimental variances were in agreement. However, large discrepancies were observed for all sampling stages of both procedures between absolute theoretical and experimental relative variances. In the case of Pb, theoretical calculations were closer to experimental measurements when using a calculated value of the liberation factor (l) based on mineralogical data rather than l= 1. It was shown that the b-exponent had a large influence on theoretical variances. Increasing the estimate of b from 0.5 to 1 largely improved the agreement between theory and experiment. Finally, 99% of experimental relative variance was explained by sampling errors compared to analytical errors. © 2012 Elsevier B.V.

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