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Résumé :
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The municipal landfill at the Complexe Environnemental de Saint-Michel (CESM) in Montreal, which is:the third largest in North America, is located in a former quarry in fractured limestone. Impressive measures are-taken to monitor and control biogas and leachate: generated at the site. Leachate containment is presently performed with a pumping well completed within the waste. The efficiency of the well in controlling off-site leachate migration is questioned because field observations strongly suggest that:the nearby former Francon quarry is diverting local: ground water flow. To address this issue, four additional hydraulic control options are considered: (1) increased pumping at the existing waste well; (2) new pumping Wells;in The rock on the eastern limit of the site: (3) new injection wells in the rock on the eastern limit; and (4) combination Of:new injection wells at the same location and new water:supply wells upgradient of the landfill. We evaluated:the four hydraulic control options at the CESM using two,coupled models: (1)a decision model based on an objective function weighting the risk, costs, and benefits-of each option translated into dollar units; and (2) a numerical ground water flow model-to represent the effect of operational conditions and ascertain success. Decision analysis offers a quantitative unbiased tool to evaluate the potential and relative: cost of each option, but qualitative considerations and judgement:still must-be used for a complete evaluation. Our analysis confirms that scenario 4, which was the intuitively favored option, represents the best containment strategy.
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