Which of the following is NOT a geologic factor affecting contaminant movement?

• A. Groundwater hydrology, aquifer porosity/permeability
• B. Topography
• C. Seasonal rainfall and drought patterns
• D. Soil type

Answer: (C)

Contaminant movement in groundwater is governed by features of the subsurface and the landscape that control how water and dissolved substances travel: the makeup and properties of the geologic materials, how easily water can move through them (porosity and permeability), the soils present, and the way the land’s slope guides flow. Seasonal rainfall and drought patterns, on the other hand, are climatic and hydrologic conditions that change recharge, water levels, and dilution, but they do not alter the geologic properties of the subsurface. They influence when and how much water is available to move contaminants, not the inherent pathways and storage features that govern movement. So, the factor that is not a geologic factor is the seasonal rainfall/drought pattern, since it’s a climate/hydrology driver rather than a geologic property of the subsurface.