Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Freeze & Cherry, Groundwater (Darcy's Law, vadose zone); CCME, Guidance Document on Landfill Gas Management; EGBC/Engineers Canada 04-Env-A6/18-Env-A6 examination syllabus.