Groundwater monitoring wells are __ sampled for residual chlorine.

• A. NOT
• B. Always
• C. Sometimes
• D. Never

Answer: (A)

Residual chlorine is a measure tied to disinfection in treated water and distribution systems, not to the natural quality of groundwater. In groundwater, any chlorine residual typically dissipates quickly as water moves through soil and rock and reacts with minerals and organic matter. Because of this rapid decay and the lack of meaningful, stable information about groundwater quality from such a measurement, sampling for residual chlorine is not a routine practice in groundwater monitoring wells. The normal purpose is to assess contaminants and natural groundwater conditions, not to check disinfection residuals. That’s why this would be described as not sampled in standard groundwater monitoring.