18-Env-A1 Principles of Environmental Engineering · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2014 — 04-Env-A1 / Principles of Environmental Engineering. 3 hours duration; closed book with an 8.5×11 in double-sided aid sheet; Casio or Sharp approved calculator only. Any five questions constitute a complete paper (first five answers marked); all seven are solved below for completeness. Each question is worth 20 marks.
Reference texts. Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery (5th ed.); MWH’s Water Treatment: Principles and Design (3rd ed.); Guidelines for Canadian Drinking Water Quality (Health Canada); Canadian Council of Ministers of the Environment (CCME) water-quality guidelines; Canadian Environmental Protection Act, 1999 (CEPA); Andrews, Canadian Professional Engineering and Geoscience (professional ethics).
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.
An environmental impact assessment systematically identifies the redevelopment's activities, predicts their effects on the downstream reservoir, and builds mitigation into the project before approval — it works because it is applied at the planning stage, when process alternatives and mitigation are still cheap to change, rather than after construction when only end-of-pipe fixes remain. Because a silver–copper ore body is typically sulphide-hosted, the EIA is organized around the process steps that create acid- and metal-mobilization risk to the reservoir:
| Process Step | Key Issue | Consideration | Mitigating Action |
|---|---|---|---|
| Mine reopening / waste-rock exposure | Acid rock drainage (ARD) and metal (Cu, Ag, Zn) leaching from re-exposed sulphide waste rock | Historical waste-rock and tailings sulphide content; upstream position relative to the reservoir | Acid-base accounting to segregate potentially-acid-generating rock, engineered covers, seepage collection and treatment before it reaches the watershed |
| Ore processing (flotation / leaching) | Process reagent and dissolved-metal release to water | Tailings pond location and seepage pathway relative to reservoir inflow | Lined tailings impoundment, closed-loop process water recirculation, discharge permit with reservoir-protective limits |
| Tailings storage facility | Long-term dam stability and seepage into the watershed feeding the reservoir | Downstream reservoir intended as a drinking-water source | Independently reviewed engineered dam design, real-time seepage/groundwater monitoring wells upgradient of the reservoir, emergency response plan |
| Site drainage / runoff management | Sediment and metal-laden surface runoff during construction and operation | Watershed hydrology draining toward the reservoir | Sediment ponds and diversion ditches routing clean water around disturbed areas, erosion and sediment control plan |
| Mine closure | Perpetual ARD generation after operations cease | Reservoir remains a drinking-water source in perpetuity | Progressive reclamation, financial closure bond sized for perpetual water treatment if needed, walk-away water-treatment design |
The matrix format is itself part of the mitigation: by pairing each process step with a specific issue and a specific, assignable action tied to protecting the downstream drinking-water use, the EIA avoids generic mitigation language and produces commitments the regulator (in BC, under the Environmental Assessment Act, with the reservoir's use as a drinking-water source elevating the standard of protection required) can hold the proponent to through permitting, operation and closure.
The Brundtland definition of sustainable development — development that meets the needs of the present without compromising the ability of future generations to meet their own needs — rests on three interlocking pillars: environmental integrity, economic viability and social equity, evaluated together rather than any one in isolation. Applied to achieving energy self-sufficiency, no source is unconditionally "sustainable"; the question is how it performs against the three pillars across its full life cycle.
Taking wind power as the chosen source: over its operating life it produces electricity with essentially zero direct greenhouse-gas or air-pollutant emissions, strongly favouring environmental integrity and displacing fossil generation whether deployed on-site (e.g., a single turbine serving an isolated community or facility) or at a centralized wind farm feeding the grid. A full life-cycle analysis (LCA), however, tracks impacts across raw-material extraction (rare-earth mining for permanent-magnet generators, steel and concrete for towers/foundations), manufacturing, transport, installation, decades of operation, and decommissioning/recycling of blades (glass-fibre composite blades are currently difficult to recycle and are a growing end-of-life waste stream). LCA studies consistently show wind's lifecycle greenhouse-gas intensity (roughly 10–15 g $\text{CO}_2$-eq/kWh) is one to two orders of magnitude below coal or natural gas, and its energy payback time (the time to generate the energy invested in manufacturing it) is typically under one year against a 20–25 year service life — a favourable energy-return-on-investment that a continuously-fuelled thermal source cannot match. Where wind falls short of full energy self-sufficiency is intermittency: a site or grid relying on wind alone needs storage or backup generation (which carries its own life-cycle burden) to cover low-wind periods, and centralized wind farms require transmission infrastructure that an on-site installation avoids but at smaller, less efficient scale. The LCA-informed conclusion is that wind power scores strongly on the environmental pillar and favourably on long-run economics, but genuine energy self-sufficiency (on-site or centralized) requires pairing it with storage/grid solutions and a credible end-of-life blade-recycling pathway for the social and full-environmental pillars to be satisfied as well.
