16-Civ-A3 Elementary Environmental Engineering · May 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. National Exams 98-Civ-A3 Environmental Engineering, May 2014 — 3 hours, closed book with one candidate-prepared double-sided aid sheet, approved Casio or Sharp calculator only. Seven questions are offered; any five constitute a complete paper (20 marks each, 100 marks maximum), and only the first five answers in the work book are marked. All seven are solved here, because the set is intended as a study resource rather than an examination script. Section marks are shown in brackets at the left margin of each part, and the marking scheme on page 6 confirms the split.
Reference texts. Davis & Cornwell, Introduction to Environmental Engineering (5th ed.); Mihelcic & Zimmerman, Environmental Engineering: Fundamentals, Sustainability, Design (3rd ed.); Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery (5th ed.); Crittenden et al., MWH’s Water Treatment: Principles and Design (3rd ed.). Canadian regulatory frame: the federal Impact Assessment Act (2019) and the Impact Assessment Agency of Canada, the Canadian Environmental Protection Act (CEPA 1999), CCME Canadian Environmental Quality Guidelines, and Health Canada’s Guidelines for Canadian Drinking Water Quality (GCDWQ).
Check: Henry’s law constant units in Question 1(i). The paper writes the constant as “0.30 (mol/atm)”, which is dimensionally incomplete — a Henry’s constant in the concentration/pressure form must carry a volume in the denominator. It is taken here as 0.30 mol/(L·atm), i.e. the aqueous-concentration form $C_{aq}=K_H\,p$. That reading is confirmed by the published value for ethyl acetate, $H \approx 1.3\times10^{-3}\ \text{atm}\cdot\text{m}^3/\text{mol}$, whose reciprocal is $\approx 0.77\ \text{mol}/(\text{L}\cdot\text{atm})$ — the same order of magnitude. Per NOTE 1 on page 1, this assumption is stated with the answer.
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.
The question asks for two impacts and two corresponding engineering solutions in each of nine cells. The matrix below answers all nine, and the discussion that follows draws out the mechanisms that make each column distinct: population growth raises intensity of demand within a fixed footprint, economic growth changes the character of the loading, and sprawl expands the footprint itself.
| Population Growth & Intensification (a) | Economic Growth & Industrial Activity (b) | Urban Sprawl (c) | |
|---|---|---|---|
| Watershed | Impacts: (1) higher imperviousness raises peak runoff and flashiness, eroding stream banks; (2) elevated chloride, nutrient and pathogen loads from road salt, lawns and pet waste degrade receiving-water quality. Solutions: (1) low-impact development — bioretention cells, permeable pavement, green roofs — to restore infiltration and match pre-development runoff volume; (2) stormwater quality ponds and treatment trains with a source-control salt-management plan. |
Impacts: (1) point-source discharge of process effluent carrying metals, solvents and thermal load; (2) contaminated-site legacy and groundwater plumes from historic storage and spills. Solutions: (1) industrial pretreatment and sewer-use bylaw enforcement with effluent limits and self-monitoring at each outfall; (2) site characterisation and remediation — pump-and-treat, permeable reactive barriers, in-situ bioremediation — to CCME and provincial standards. |
Impacts: (1) loss of headwater streams, wetlands and riparian buffer to greenfield conversion, removing natural attenuation; (2) fragmentation of habitat and interruption of groundwater recharge areas. Solutions: (1) watershed and subwatershed planning with statutory protection of natural-heritage systems and recharge areas; (2) stream and wetland restoration with compensation ratios and enforced riparian setbacks. |
| Water Infrastructure | Impacts: (1) treatment and conveyance capacity exceeded, causing low pressure and combined-sewer overflows during wet weather; (2) accelerated deterioration of aging mains under increased demand and pressure cycling. Solutions: (1) demand management — universal metering, volumetric rates, high-efficiency fixtures — which defers plant expansion at a fraction of the capital cost; (2) asset-management-driven renewal with trenchless rehabilitation, plus inflow-and-infiltration reduction and sewer separation. |
Impacts: (1) shock and slug loads that upset biological treatment and cause permit exceedances; (2) large industrial water withdrawals competing with municipal supply. Solutions: (1) equalisation basins with real-time monitoring and surcharge agreements that price the load; (2) water reuse and closed-loop cooling within the plant, with reclaimed municipal effluent supplied for industrial process use. |
Impacts: (1) very high linear cost per capita — more pipe, more pumping, more energy per household served; (2) long residence times in oversized mains cause loss of disinfectant residual, nitrification in chloraminated systems, and taste-and-odour complaints. Solutions: (1) staged servicing tied to density thresholds and full-cost development charges, so growth pays for growth; (2) hydraulic modelling with automatic flushing devices, booster chlorination and right-sized mains to maintain residual and fire flow. |
| Solid Waste | Impacts: (1) rising per-capita generation shortens remaining landfill life within an already constrained urban land base; (2) collection traffic, noise and diesel emissions intensify in dense neighbourhoods. Solutions: (1) source-separated organics and recycling with pay-as-you-throw volume-based rates and extended producer responsibility; (2) automated side-loading collection, transfer stations and route optimisation, with in-building chute separation in high-rise developments. |
Impacts: (1) generation of hazardous and industrial special waste requiring cradle-to-grave management; (2) growing volumes of construction, renovation and demolition debris. Solutions: (1) manifested hazardous-waste handling under provincial regulation with licensed treatment and disposal, backed by industrial waste audits and toxics-use reduction; (2) mandatory construction-waste diversion plans with on-site source separation and concrete, wood and gypsum recycling. |
Impacts: (1) long haul distances raise collection cost and greenhouse-gas emissions per tonne; (2) pressure to site new landfills on the urban fringe, generating land-use conflict and groundwater risk. Solutions: (1) strategically located transfer stations with high-capacity trailer haul, and low-carbon collection fleets; (2) regional waste-management planning with engineered composite liners, leachate collection and landfill-gas capture with energy recovery. |
(a) Population growth and intensification. The defining feature of intensification is that demand grows while the servicing footprint does not, so the binding constraint is capacity rather than extent. Hydrologically, the transformation from pervious to impervious surface is what matters: research consistently finds stream degradation beginning near 10 % total impervious cover and becoming severe beyond about 25 %, because the runoff coefficient rises, the time of concentration shortens, and the receiving stream sees flashier and more erosive flows with less baseflow between storms. The correct engineering response is to treat volume at source through low-impact development rather than only to convey it faster, since conveyance simply moves the problem downstream. On the infrastructure side, intensification is precisely the situation in which demand management is most cost-effective: a plant expansion is a lumpy, expensive, long-lead capital project, whereas metering and efficiency measures buy capacity incrementally and immediately, and in most Canadian cities have deferred expansion by a decade or more.
(b) Economic growth and industrial activity. Industry changes the nature of the loading rather than merely its magnitude. Municipal treatment plants are designed for a fairly predictable domestic waste stream, and their biological processes are vulnerable to what industry contributes: metals that inhibit nitrifiers, solvents that are not biodegradable, extremes of pH and temperature, and slug discharges that arrive over minutes rather than hours. The primary control is therefore regulatory and economic rather than structural — a sewer-use bylaw setting numerical limits, requiring pretreatment and self-monitoring, and pricing the load so the generator has a direct financial incentive to reduce it. This is also the column where the historical legacy is heaviest: contaminated sites from decades of industrial activity, where remediation to CCME and provincial standards is often the largest single environmental cost of urban redevelopment.
(c) Urban sprawl. Sprawl expands the footprint, and its distinctive impacts are those of low density: linear infrastructure cost per capita rises steeply, the greenfield conversion consumes the headwater streams and wetlands that provide free attenuation, and haul distances for both water and waste lengthen. The counter-intuitive water-quality consequence deserves emphasis — mains sized for future build-out carry too little flow at first, so water ages, the disinfectant residual decays, and nitrification can take hold in chloraminated systems, producing a quality problem caused by oversizing rather than undersizing. The engineering solutions are as much financial and planning instruments as physical works: full-cost development charges and staged servicing tied to density thresholds internalise the true cost of low-density growth, which is the only durable way to change the pattern.
