The CGP required the following monitoring elements for all risk levels.

• A. Visual monitoring only
• B. Visual monitoring and monitoring of non-visible pollutants, as needed
• C. Non-visible monitoring only
• D. Flow monitoring

Answer: (B)

The monitoring approach in the CGP relies on two elements operating together: visual monitoring of stormwater discharges and, when indicated, monitoring for non-visible pollutants. Visual monitoring lets you spot obvious problems like sediment plumes, staining, or signs that control measures aren’t working. But some pollutants aren’t visible to the eye, so you also need the ability to check for non-visible contaminants when previous observations or data suggest they might be present. The phrase “as needed” ensures you perform targeted non-visible monitoring only when it’s warranted by evidence from visual checks or other data, making the monitoring program efficient and responsive.

Relying on visual monitoring alone would miss dissolved or particulate pollutants that aren’t visible. Relying on non-visible monitoring alone would miss clear, visible problems that indicate improper control measures. Flow monitoring isn’t universally required for all risk levels, so it isn’t included as a standard element for every case.