Groundwater monitoring can be used only if the product stored in the tank does what with water?

• A. Dissolves in water
• B. Sinks to bottom
• C. Floats on the water’s surface and does not mix with water
• D. Reacts with water

Answer: (C)

Groundwater monitoring works best when the stored product forms a separate liquid layer on top of the water, so you can detect it as a distinct phase. That happens when the product is immiscible with water and less dense than water, so it floats on the surface and doesn’t mix in. If the product dissolves in water, sinks, or reacts with water, it won’t create a detectable free layer, making groundwater monitoring ineffective. So the scenario that allows monitoring to be used is when the product floats on the water’s surface and does not mix with water.