Which pair of risk factors is considered primary when evaluating potential environmental impact of stormwater?

• A. Receiving Waters and Sediment Risk
• B. Species habitat and water temperature
• C. Soil erosion rate and project cost
• D. Air quality and noise levels

Answer: (A)

When evaluating stormwater’s environmental impact, the most important concerns are where the runoff ends up and what it carries. Receiving waters identify the exposure pathway—the streams, rivers, or lakes that receive the runoff and thus the potential effects on water quality and aquatic life. Sediment risk is central because sediment in stormwater can transport attached pollutants, increase turbidity, and smother habitats, driving significant ecological and water-quality impacts. Together, these two factors cover the primary box of concerns: impact on the water bodies receiving the runoff and the pollutants carried by that runoff.

Other factors touch on ecological or planning aspects but don’t drive the immediate stormwater pollution risk in the same way. Species habitat and water temperature are important ecological considerations, but they’re downstream effects rather than the direct runoff risk. Soil erosion rate and project cost relate more to BMP design and economics, and air quality and noise deal with different environmental dimensions altogether.