Which of the following is NOT typically considered a pollutant under the NPDES program?

• A. Oil and grease
• B. Heavy metals
• C. Pesticides
• D. Clean rainwater

Answer: (D)

The identification of clean rainwater as NOT typically being considered a pollutant under the NPDES (National Pollutant Discharge Elimination System) program is correct. The NPDES program regulates discharges of pollutants into waters of the United States and is designed to prevent water pollution. Pollutants under this program include various substances that can contaminate water resources, such as oil and grease, heavy metals, and pesticides, which can adversely affect the quality of water.

Clean rainwater, however, is naturally occurring and is not considered a pollutant because it does not carry contaminants or pollutants with it as it falls. It is essential to differentiate between rainwater and runoff that may pick up pollutants from impervious surfaces (like roads or parking lots), which occurs when rainwater interacts with those surfaces. In its pure form, clean rainwater is not a pollutant under NPDES regulations, making this the correct answer.