Question 7 of 7: Water Resource Management, the Greenhouse Effect and Regulatory Principles

Question 7: Water Resource Management, the Greenhouse Effect and Regulatory 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) On-Site Stormwater Control: a Bioretention Cell

A common on-site stormwater control measure is a bioretention cell (rain garden) — a shallow, vegetated depression built into a parking lot, roadway or landscaped area that intercepts runoff before it leaves the site. Two basic design features that improve quality or reduce discharged quantity:

1. An engineered filter-media bed with vegetation. A layered soil/sand/mulch media planted with deep-rooted native vegetation promotes infiltration and provides physical filtration plus biological/chemical adsorption of pollutants (suspended solids, metals, some nutrients and hydrocarbons) as runoff percolates through it — directly improving the quality of any water that does eventually leave the site.
2. A ponding zone with a flow-control (restricted) underdrain or orifice. A shallow surface ponding depth above the media provides temporary detention storage, and a restricted outlet (orifice or flow-control underdrain) releases the stored water slowly rather than allowing it to pass straight through — attenuating the peak discharge rate and reducing the total off-site discharge volume for smaller, more frequent storm events (some of which infiltrates and evapotranspires rather than ever leaving the site at all).

(ii) Two Greenhouse Gas Emission Control Strategies Compared

Two different GHG emission-control strategies:

1. Market-based carbon pricing (a carbon tax or cap-and-trade system). A price is placed on each tonne of GHG emitted (directly via a tax, or indirectly via a tradable emissions allowance under a declining cap), letting each emitter decide for itself the cheapest way to reduce emissions or to pay the price instead.
2. Prescriptive technology/performance mandates (e.g., a renewable-portfolio standard or a mandated emissions-intensity limit). Regulation directly requires a specified technology, fuel mix or maximum emissions intensity (e.g., a minimum percentage of renewable electricity, or a maximum g CO₂/kWh for new generation), leaving emitters little choice in the compliance pathway.

Environmental effectiveness: the prescriptive mandate gives more certainty that a specific, verifiable reduction will occur (the technology or intensity limit is directly checkable), whereas a carbon price’s environmental outcome depends on how emitters respond to the price signal and can be less certain in the short term, though a well-designed cap-and-trade scheme with a hard, declining cap does guarantee the aggregate reduction by design (the tax alone does not guarantee a specific tonnage reduction, only a cost incentive toward one).

Economic effectiveness: carbon pricing is generally more cost-effective at the system level, because it lets abatement happen wherever it is cheapest across the whole economy (each emitter reduces up to the point where further reduction costs more than the carbon price, and no further), whereas a uniform prescriptive mandate forces the same technology/intensity requirement on every emitter regardless of their individual abatement cost, which can impose a much higher aggregate economic cost for the same total tonnes reduced. In practice, many developed-country GHG programs combine both: broad carbon pricing for cost-effective, economy-wide abatement, plus targeted prescriptive standards in sectors (e.g., building codes, vehicle-efficiency standards) where price signals alone are known to be slow to change deeply entrenched purchase or construction decisions.

(iii) Technical and Non-Technical Approaches to VOC Emissions Near a Residential Community

A technical (engineering-control) approach: installing vapour-recovery or activated-carbon adsorption units on process vents and storage-tank breathing losses across the industrial park, capturing VOCs at their point of release before they reach the ambient air near the residential community.

A non-technical (policy/land-use) approach: establishing a mandatory buffer/setback zone (or land-use planning restriction) between the industrial park and the residential community, combined with a facility-reporting and community-notification program for VOC-emitting activities — reducing exposure and risk through separation and transparency rather than through hardware on any individual source.

The two are complementary rather than substitutes: the technical measure reduces the VOC mass actually emitted, while the non-technical measure reduces the population’s exposure to whatever residual emissions remain and to the cumulative effect of the whole industrial park rather than any single source.