18-Env-A6 Solid Waste Engineering and Management · December 2017
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; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); Freeze & Cherry, Groundwater; CCME, Guidance Document on Landfill Gas Management; Canadian Environmental Protection Act, 1999.
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.
Extending a landfill's remaining life means either reducing the annual volume consumed or increasing the airspace available (or both), so a complete strategy addresses both sides. Reduce input: expand waste diversion — mandatory recycling and organics (food/yard waste) collection removes both bulky and readily biodegradable material from the waste stream; volume-based ("pay-as-you-throw") user fees give households and businesses a direct financial incentive to divert; and construction & demolition debris diversion targets a material category that is otherwise dense and space-consuming. Increase capacity utilization: improve in-place compaction (heavier/dedicated compactors, thinner working lifts, tighter cell geometry) to raise the achieved density above the design assumption; switch from soil daily cover to alternative daily cover (tarps, foam or spray-applied products), which consume essentially no airspace compared with 15–20 cm of soil applied every operating day; and consider leachate recirculation (bioreactor landfill operation), which accelerates waste settlement and stabilization, freeing airspace faster than a conventional "dry tomb" cell. Add capacity: pursue permitted vertical expansion (increasing final grades) where geotechnical stability and any height/aesthetic restrictions allow, or lateral expansion onto adjacent land if available and can be permitted; and consider landfill mining of an older, well-decomposed cell (Question 7) to reclaim settled airspace. Support measures: a public education and engagement campaign to sustain diversion participation, and periodic waste-composition auditing to verify the strategy is targeting the material that actually dominates the incoming waste stream.
