18-Env-A6 Solid Waste Engineering and Management · December 2013
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; Freeze & Cherry, Groundwater (Darcy's Law, vadose zone); CCME, Guidance Document on Landfill Gas Management; EGBC/Engineers Canada 04-Env-A6/18-Env-A6 examination syllabus.
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.
13.1 A defensible approach combines direct measurement with a structured sampling plan. First, stratify the community by waste source category (single-family residential, multi-family residential, commercial, institutional, industrial), since generation rates and composition differ systematically between them. For each stratum, conduct a load-count and weigh-scale survey (Q12) at the disposal or transfer facility over a representative period, recording both the total mass collected and the source of each load. In parallel, perform periodic composition (sort) studies — physically sorting representative samples of collected waste into standard categories (paper, organics, plastics, metal, glass, etc.) following an established protocol (e.g., ASTM D5231) — to establish percentage composition by source. Data should be collected across multiple seasons (see 13.2) and cross-checked against per-capita/per-employee generation factors from comparable communities as a sanity check on the direct measurements. The final report presents generation rates (kg/capita/day or kg/source/day) and composition (% by category) broken out by source, with the sampling methodology and any assumptions stated explicitly.
13.2 With only 30 days and no ability to observe a full annual cycle, seasonal variation cannot be measured directly and must instead be estimated from published factors: apply seasonal adjustment ratios drawn from comparable communities of similar size, climate and land use (available from provincial waste-management agencies, prior regional studies, or the technical literature), scaling the short-term measured rate up or down for the season actually sampled. If the 30-day study is conducted, for example, in a low-generation season (winter, less yard waste), the measured rate is adjusted upward by the published seasonal ratio to estimate the annual average; the adjustment factor and its source must be clearly stated as an assumption in the report, since it is the single largest source of uncertainty in a short-duration study.
