The purpose for a double-cased monitoring well would be...

• A. To improve water yield
• B. To allow easier drilling
• C. To prevent migration of contamination between aquifers
• D. To reduce pumping energy

Answer: (C)

A double-cased monitoring well is designed to keep aquifers separate along the wellbore so water and contaminants can’t move vertically between them through the borehole. This isolation ensures that samples reflect the specific aquifer of interest and that the data aren’t contaminated by water from an overlying or underlying layer. In settings with multiple aquifers that have different water quality or pressures, this ability to prevent cross-communication is essential for accurate groundwater monitoring and for assessing whether contamination could migrate between layers. The other options don’t fit the purpose: increasing yield, easing drilling, or reducing pumping energy aren’t goals of a monitoring well, where the priority is maintaining separation and data integrity.