Question 6 of 7: Water Resource Management, Greenhouse Effect, Noise Pollution and Technical/Non-Technical Principles

Question 6: Water Resource Management, Greenhouse Effect, Noise Pollution and Technical/Non-Technical Principles (20 marks)

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) Protecting a Coastal Aquifer from Seawater Intrusion

Two water resource management strategies protect a coastal drinking-water aquifer from seawater (saltwater) intrusion caused by ocean water encroachment:

1. Managed groundwater abstraction (pumping management). Reduce, redistribute, or cap withdrawal rates — through well-field redesign (spreading pumping over more, more widely spaced wells rather than a few high-capacity wells) and seasonal/permitted pumping limits — to keep the freshwater hydraulic head high enough that the freshwater–saltwater interface stays seaward of the supply wells and does not "upcone" beneath them.
2. Artificial recharge / hydraulic barrier. Inject or spread treated water (reclaimed effluent, stormwater, or surplus surface water) through recharge wells or infiltration basins along the coast to build a freshwater mound that hydraulically pushes back against seawater intrusion; in severe cases a physical subsurface barrier (e.g., a slurry cut-off wall) can be constructed to directly block the intrusion pathway.

(ii) Main Man-Made Cause of the Greenhouse Effect and Two Technical Solutions

The principal man-made cause of the enhanced greenhouse effect is the combustion of fossil fuels (coal, oil, natural gas) for electricity generation, transportation and industry, which releases carbon dioxide (and, from agriculture and waste, methane) faster than natural sinks can absorb it, increasing the atmospheric concentration of greenhouse gases and enhancing the trapping of outgoing long-wave radiation. Two technical solutions: (1) transition to low-carbon energy generation and efficiency improvements — renewable electricity (wind, solar, hydro) and nuclear power displacing fossil combustion at the source, combined with building/industrial energy-efficiency measures that reduce the total combustion required in the first place; and (2) carbon capture and storage (CCS) at large stationary point sources (power plants, cement/steel plants), which captures CO₂ before or after combustion and sequesters it geologically, directly reducing emissions from sources that cannot yet be fully decarbonized by fuel-switching alone.

(iii) Noise Control for a Stone Crushing Operation Near a Residential Community

Two engineering methods reduce noise pollution reaching a residential community within 1 km of a stone crushing operation:

1. Source control — acoustic enclosure of the crusher. Enclosing the crusher (and associated conveyors/screens) in a sound-attenuating housing with absorptive interior lining reduces the sound power radiated at the source itself, typically achieving a large (10–20 dB class) reduction independent of wind direction or distance to any particular receptor.
2. Path control — distance, berms and vegetative/engineered barriers. Increasing the buffer distance between the crusher and the community, and/or constructing an earthen berm or solid noise barrier wall (with vegetative screening) along the transmission path, attenuates sound before it reaches the receptor; sound intensity from a point source falls off with distance (roughly 6 dB per doubling of distance for unobstructed spherical spreading), so distance and barriers work together to reduce the received level.

Preferred method: source enclosure. Because it reduces the sound power emitted in every direction at once, an enclosure protects the community regardless of wind direction, atmospheric temperature gradients (which can otherwise enhance downwind or inversion-condition propagation and defeat a barrier's benefit), or the exact site layout, whereas a barrier or added distance only attenuates along specific propagation paths and can be undermined by favourable-propagation weather conditions. Source control is therefore the more robust and reliable long-term solution, with path controls (berms, siting distance) serving as a useful secondary/complementary measure.

(iv) Technical vs. Non-Technical Principles for Diesel Truck Fleet Emissions Near a Retirement Community

A technical environmental principle here is emissions-reduction hardware/technology: retrofitting the truck fleet with diesel particulate filters (DPF) and selective catalytic reduction (SCR) for NOx control, or transitioning the fleet toward lower-emission or electric trucks. This gives a permanent, verifiable per-vehicle emission reduction that holds regardless of driver behaviour, but requires significant capital investment and a fleet-turnover timeline before benefits are fully realized. A non-technical principle is administrative/policy control: routing restrictions or a low-emission/truck-restricted zone designation along the highway stretch adjacent to the retirement community, idling bylaws, or scheduling deliveries away from times when the vulnerable population (elderly residents with elevated respiratory sensitivity) is most exposed. This is inexpensive and can be implemented immediately, but relies on ongoing compliance and enforcement, and only shifts where and when exposure occurs rather than reducing total fleet emissions. The two approaches are complementary rather than substitutes: technology reduces the emissions each truck produces, and policy controls where and when the (reduced-emission) fleet operates relative to the most sensitive receptors, giving the greatest net protection to the retirement community when applied together.