18-Env-A6 Solid Waste Engineering and Management · May 2016
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.); 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.
16.1 Reasons to consider landfill mining. (1) Recover airspace to extend the site's remaining operating life without acquiring new land. (2) Recover marketable materials — ferrous and non-ferrous metals, and increasingly recoverable soil fines and combustibles/RDF — buried in older waste. (3) Reduce long-term environmental liability by removing or relocating a leachate- and gas-generating waste mass, for example ahead of site remediation or redevelopment. (4) Reclaim the land for a higher-value future use, whether outright redevelopment or re-siting a modern, fully lined cell on the same footprint.
16.2 Health and safety requirements. Continuous atmospheric monitoring for methane, hydrogen sulphide, other VOCs and oxygen deficiency across the excavation; respiratory and other appropriate personal protective equipment; excavation and slope-stability controls with exclusion zones around active equipment; fire and explosion precautions (no uncontrolled ignition sources, bonded/grounded equipment); biological-hazard controls (exposure to pathogens and sharps, vector control); heavy-equipment traffic management; and a site-specific health and safety plan with documented worker training.
16.3 Items to consider in the work plan. Pre-mining site characterization (test pits/boreholes to determine waste depth, age and composition, and any contamination); an excavation and processing sequence (screening/trommelling to separate soil fines, recyclables, combustibles and residual waste for re-disposal); a materials management plan for each recovered stream; environmental controls during mining (dust suppression, odour management, leachate handling, temporary stormwater control); the health and safety plan (16.2); a monitoring and quality-assurance program; a schedule and cost estimate; the required regulatory approvals/permitting; and a stakeholder communication plan, since mining operations are visibly disruptive and can generate odour complaints from surrounding land uses.
