What factor determines whether an overflow or underflow dam is used to contain a spilled liquid during containment operations?

• A. Temperature
• B. Specific gravity relative to water
• C. Color
• D. pH level

Answer: (B)

The key factor is how the spilled liquid behaves in water—whether it floats or sinks. This is determined by its specific gravity relative to water. If the liquid is lighter than water (specific gravity less than 1), it rests on the surface, so you use an overflow dam to capture it as it rises and overflows into the containment area. If the liquid is heavier than water (specific gravity greater than 1), it will sink to the bottom, so an underflow dam is used to trap it at the bottom and prevent it from spreading.

Temperature, color, or pH don’t decide the dam type; they may affect other hazards or handling, but not whether the liquid will layer on or under the water.