Which condition indicates vulnerability to surface water intrusion?

• A. Shallow depth, missing or poor sanitary seal, and proximity to surface water or contamination sources.
• B. Deep depth and excellent sanitary seals
• C. Use of a modern filtration system
• D. Proximity to a mountain

Answer: (A)

Vulnerability to surface water intrusion is highest when a well is shallow, lacks a proper sanitary seal, and sits near surface water or contamination sources. A shallow well has less overburden to filter contaminants and is closer to where pollutants enter the groundwater. A missing or poor sanitary seal around the casing provides a direct pathway for surface water and contaminants to reach the inside of the well. Being near surface water bodies or known contamination sources increases the likelihood that contaminants will reach the groundwater feeding the well. In contrast, deeper wells with a strong sanitary seal are better protected because deeper groundwater is more naturally filtered and the seal blocks entry. A modern filtration system treats water after withdrawal rather than preventing intrusion at the source, and being near a mountain isn’t a factor in surface water intrusion risk.