Under what circumstances may the Department reduce monitoring frequency for nitrate at a surface water sampling point and what is the reduced frequency?

• A. If analytical results are < 5 mg/L for 4 consecutive quarters then reduce sampling frequency from quarterly to annually.
• B. If analytical results are < 5 mg/L for 2 consecutive quarters then reduce sampling frequency from quarterly to annually.
• C. If analytical results are > 5 mg/L for 4 consecutive quarters then reduce sampling frequency from quarterly to annually.
• D. If analytical results are < 10 mg/L for 3 quarters then reduce sampling frequency from quarterly to annually.

Answer: (A)

Steady, long-term low nitrate levels allow the department to reduce how often monitoring is done. If nitrate results stay below 5 mg/L for four consecutive quarters, it shows the water typically remains within safe or acceptable levels across different seasons. That consistent performance supports switching from quarterly sampling to an annual schedule, since the likelihood of sudden spikes is low and regulatory oversight can still be maintained with less frequent checks.

Two consecutive quarters below 5 mg/L doesn’t prove stability across all seasons, so it’s not enough to justify less frequent monitoring. Four consecutive quarters with results above 5 mg/L indicate higher concentrations and no basis for reducing frequency. A criterion like three quarters below 10 mg/L isn’t the established trigger and still doesn’t demonstrate a full year of stable, low levels, so it wouldn’t justify moving to annual sampling.