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18-Env-A6 Solid Waste Engineering and Management · May 2017

Question 5 of 16: Sanitary Landfill Cross Section

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

National Examination, May 2017 — 04-Env-A6 / 18-Env-A6, Solid Waste Engineering and Management. 3 hours duration, closed book, non-communicating calculator permitted. All 16 questions constitute a complete paper (100 marks total).

Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); CCME, Guidance Document on Landfill Gas Management; ISO 14040/14044, Environmental Management — Life Cycle Assessment.

Q6 below is solved from the six printed per-component rows, which are unambiguous exam-given data — see the callout at Q6 for the arithmetic. Table 2's "5.800 kJ/kg" organics value (period instead of comma) is read as 5,800 kJ/kg.

Question 5: Sanitary Landfill Cross Section (5 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Native subgrade soilComposite liner (compacted clay + geomembrane)Leachate collection / drainage layerLeachatesumpLift 1: compacted refuseLift 2: compacted refuseLift 3: compacted refuseDaily / intermediate soil cover (between lifts)Barrier + drainage layer (final cap)Topsoil + vegetationGas ventGroundwatermonitoring wellPerimeterbermAccess road / working face beyond →
Cross section of a modern sanitary landfill cell, from the composite liner system at the base through successive compacted refuse lifts to the final cover cap, with the ancillary leachate, gas and monitoring systems that a complete design must include.

From bottom to top: (1) the native subgrade soil, graded and proof-rolled to receive the liner; (2) a composite liner system (compacted clay plus a synthetic geomembrane), the primary hydraulic barrier between refuse and native soil/groundwater; (3) a leachate collection and drainage layer directly above the liner, sloped to a network of perforated collection pipes conveying leachate to a collection sump; (4) successive compacted refuse lifts, each separated by a thin daily/intermediate soil cover controlling odour, vectors, blowing litter and fire risk during operation; (5) a vertical landfill gas vent/collection riser releasing or actively extracting the methane-rich gas generated by anaerobic decomposition; (6) a multi-layer final cover (cap) system — barrier/drainage layer plus topsoil and vegetation — shedding infiltrating precipitation and supporting post-closure land use; (7) a perimeter berm containing the toe of the waste mass, separating the active cell from the surrounding access road; and (8) a groundwater monitoring well, screened downgradient of the liner to detect any leachate breakthrough.