To determine whether a leak exceeds GWPS, monitoring should be performed at which part of the aquifer?

• A. Uppermost
• B. At several locations in the aquifer
• C. Midpoint
• D. Lowermost

Answer: (A)

This question tests where to monitor to determine if a leak meets or exceeds the Ground Water Protection Standard. The uppermost aquifer is the first groundwater zone touched by a surface release and is the one most closely linked to drinking-water wells. Detecting contaminants in this shallow layer provides the earliest and most relevant indication of whether a release is occurring and whether it exceeds the GWPS. If monitoring were done deeper, the signal could be delayed or missed entirely, potentially allowing unsafe conditions to persist in the most vulnerable, near-surface groundwater. While sampling at multiple locations across the aquifer can help map a plume, the critical zone for assessing GWPS exceedance is the uppermost aquifer.