Under NPDES general permit rules, when is a permit required?

• A. Not required for pesticide applications
• B. Required if water more than 1 acre
• C. Required if water more than 80 acres in a calendar year, or area of shoreline >20 miles
• D. Required for air-borne pesticides

Answer: (C)

The key idea here is regulators’ thresholds for when a pesticide discharge to surface waters must be covered by an NPDES general permit. Pesticide applications that end up discharging into waters of the United States are regulated, but small, incidental discharges aren’t always subject to the permit. The general permit applies when the scale of the affected water is large enough to require formal coverage.

That’s why this option is the best: a permit is required if the water area affected by the pesticide discharge exceeds 80 acres in a calendar year, or if the shoreline area affected is more than 20 miles. These thresholds are designed to capture larger, more impactful discharges while avoiding unnecessary permitting for smaller, less significant applications.

The other possibilities don’t fit because NPDES-related requirements focus on water discharges, not air, so air-borne applications aren’t governed by this permit. And the idea that a permit isn’t needed for pesticide applications is incorrect, since discharges to surface waters do require permitting when the thresholds are met. Also, 1 acre is far below the 80-acre threshold, so the smaller figure isn’t the rule.