When located in a flood hazard area, the top of a potable water well casing without a sealed cover shall extend not less than _____ inches above the design flood elevation.

The correct answer indicates that the top of a potable water well casing without a sealed cover must extend at least 12 inches above the design flood elevation when situated in a flood hazard area. This requirement is critical for ensuring the protection of the potable water supply from potential contamination during flooding events.

By maintaining a height of 12 inches above the design flood elevation, the well is safeguarded against the inflow of floodwaters which can carry pollutants and pathogens. This elevation helps to prevent backflow and contamination that could compromise the safety and quality of the water supply.

Moreover, following this guideline reflects best practices in public health and safety, emphasizing the importance of maintaining a clear barrier between the water supply and any potential flood contaminants. Ensuring that potable water sources are elevated appropriately is crucial, especially in areas prone to flooding, thereby contributing to safe drinking water standards and overall community health protection.