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

Question 8 of 16: Strategy to Extend Landfill Life

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 8: Strategy to Extend Landfill Life (8 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.

Landfill life extension is achieved along two independent axes — reducing the annual volume that must be buried, and increasing the airspace available to bury it in — and a robust strategy pursues both. To reduce incoming volume: implement or expand diversion programs (curbside recycling, organics/yard-waste composting) to remove the largest divertible fractions before they reach the landfill face, supported by economic tools (pay-as-you-throw fees, landfill bans on specific recyclable/compostable materials) that give residents and businesses a direct incentive to divert. To increase available airspace within the existing footprint: improve compaction practice (heavier/multi-pass compactors, thinner working-face lifts) to raise in-place density, adopt vertical expansion (a taller final grade, where geotechnically and visually acceptable), and minimize the volume consumed by daily cover through alternative daily cover materials (tarps, foam, spray-applied products) instead of a full soil layer, since soil cover itself displaces refuse airspace every operating day. Where the site boundary allows, a formal lateral/horizontal expansion is the most direct way to add capacity, though it faces the same siting and community-acceptance constraints as an entirely new site. Each measure should be quantified in added years of remaining life and compared on a cost-per-year-gained basis, since a mature site combining stronger diversion with better compaction and reduced daily-cover consumption can often add several years of life at far lower capital cost than pursuing expansion alone.

None of these measures is mutually exclusive with the others — a mature site typically layers several simultaneously, since the airspace gained from better compaction and reduced daily cover is realized immediately while a lateral or vertical expansion's permitting timeline can run several years, making the near-term measures essential bridging capacity regardless of whether an expansion is ultimately pursued.