CSC Remediation & Mitigation Strategies 2 — Questions and Answers
Question 1: Which in-situ remediation technique uses microorganisms injected into contaminated groundwater to break down chlorinated solvents?
- Enhanced bioremediation (Correct answer)
- Pump-and-treat
- Soil vapor extraction
- Permeable reactive barrier
Correct answer: Enhanced bioremediation
Enhanced bioremediation introduces electron donors and specialized microbes (e.g., Dehalococcoides) to degrade chlorinated solvents like PCE and TCE in place.
Question 2: A site contaminated with arsenic-laden soil is treated by mixing iron-based amendments into the soil to immobilize the contaminant. This approach is best classified as:
- Phytostabilization
- Chemical stabilization/solidification (Correct answer)
- Monitored natural attenuation
- Thermal desorption
Correct answer: Chemical stabilization/solidification
Chemical stabilization uses amendments like iron oxyhydroxides to bind heavy metals such as arsenic, reducing their mobility and bioavailability.
Question 3: Which metric is most commonly used to evaluate the effectiveness of a carbon offset project over time?
- Net present value (NPV)
- Permanence and additionality scores (Correct answer)
- Energy return on investment (EROI)
- Total suspended solids (TSS) reduction
Correct answer: Permanence and additionality scores
Carbon offset quality is judged primarily on permanence (long-term storage) and additionality (emissions reductions beyond business-as-usual).
Question 4: A coastal municipality wants to reduce storm surge damage using nature-based solutions. Which strategy would be most effective?
- Installing concrete seawalls at all shorelines
- Restoring and expanding mangrove and wetland buffers (Correct answer)
- Raising building elevations by 2 feet
- Deploying offshore breakwater structures only
Correct answer: Restoring and expanding mangrove and wetland buffers
Mangroves and coastal wetlands attenuate wave energy, trap sediment, and sequester carbon, making them highly effective nature-based coastal defenses.
Question 5: When applying the mitigation hierarchy, which step should be addressed FIRST before considering offsets?
- Restoration of degraded habitats
- Biodiversity offsetting
- Avoidance of environmental impact (Correct answer)
- Rehabilitation of affected species
Correct answer: Avoidance of environmental impact
The mitigation hierarchy prioritizes avoid, minimize, restore, and offset in that order — avoidance of harm is always the first and preferred step.
Question 6: Soil vapor extraction (SVE) is most effective for remediating which type of contamination?
- Heavy metals in clay soils
- Volatile organic compounds (VOCs) in permeable soils (Correct answer)
- Polychlorinated biphenyls (PCBs) in sediment
- Nitrate contamination in deep aquifers
Correct answer: Volatile organic compounds (VOCs) in permeable soils
SVE applies a vacuum to extract VOC vapors from the unsaturated (vadose) zone, and works best in permeable soils with high contaminant volatility.
Question 7: A company implements a greenhouse gas reduction plan that achieves a 30% emissions cut through internal projects before purchasing offsets. This approach best reflects:
- Carbon insetting only
- A 'reduce first, offset last' mitigation hierarchy for emissions (Correct answer)
- Scope 3 accounting without Scope 1 reductions
- Greenwashing through selective disclosure
Correct answer: A 'reduce first, offset last' mitigation hierarchy for emissions
Best practice for corporate climate action requires maximizing internal emission reductions before using offsets to address residual emissions.
CSC Remediation & Mitigation Strategies 2
Which in-situ remediation technique uses microorganisms injected into contaminated groundwater to break down chlorinated solvents?