Under what conditions can the Department reduce monitoring frequency for nitrate at a surface water sampling point?

The correct choice indicates that the Department can reduce the monitoring frequency for nitrate at a surface water sampling point if the results are consistently less than 5 mg/L for four consecutive quarters. This approach is based on the understanding that consistently low nitrate levels suggest a stable environmental condition, thereby reducing the need for more frequent monitoring.

Regular monitoring of nitrate levels is critical for assessing water quality and identifying potential contamination sources. However, if a sampling point demonstrates a consistent trend of low nitrate concentrations over an extended period, it implies that the water source is likely not subject to significant nitrate contamination. This criterion provides a basis for the Department to allocate resources more efficiently, focusing monitoring efforts on areas that may be at higher risk of contamination.

The other options do not provide the same justification for reducing monitoring frequency. For instance, if results exceed 5 mg/L or are consistently around that threshold, it indicates a potential concern that necessitates continued or increased monitoring to ensure public health and safety. Additionally, budget constraints might influence monitoring strategies in practice, but they do not provide a regulatory basis for reducing frequency based on water quality results. Therefore, option B reflects a data-driven decision-making process essential for environmental management.