18-Env-A6 Solid Waste Engineering and Management · May 2015
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.
I would propose a layered strategy, since no single measure can be relied on to deliver the years of additional life council needs. On the demand side, waste-diversion programs (curbside recycling, organics/food-waste collection and composting, construction-and-demolition material recovery) directly reduce the tonnage that must be landfilled in the first place, and are typically the lowest-cost airspace-per-dollar option available. On the supply side, I would review compaction practice at the working face — optimizing compactor passes, lift thickness and, within geotechnical stability limits, steeper final side slopes and higher permitted final contours (vertical expansion) — all of which increase the tonnage placed per unit of permitted footprint without expanding the site boundary. Where an older, inactive cell exists, a landfill-mining study would assess whether excavating and screening it to recover metals/recyclables and reclaim settled airspace is economically viable.
If the existing permitted footprint has genuinely reached its geometric limit, I would evaluate horizontal expansion onto adjacent council-owned or acquirable land (subject to a new environmental assessment and hydrogeologic siting review) as a medium-term option, and, as a longer-term contingency, a transfer-and-haul arrangement to a regional facility with remaining capacity. Finally, I would recommend switching from traditional 150 mm earth daily cover to an alternative daily cover (tarpaulins, foam or thin engineered material) wherever regulations permit, since earth cover alone can consume 15–20% of a cell's total airspace over its operating life. I would present these options to council ranked by cost per year of life gained, since diversion and operational changes are typically far cheaper than a full site expansion.
