In soil-to-air corrosion inspection, the digging depth range falls within which of the following?

In soil-to-air corrosion inspection, the digging depth range falls within which of the following?

• A. 2-4 inches
• B. 6-12 inches
• C. 12-18 inches
• D. 18-24 inches

Answer: (B)

Corrosion at the soil–air boundary is driven by moisture and oxygen exchange right near the ground surface. Digging to about six to twelve inches below grade reliably exposes the pipe at this interface, so you can actually see coating damage and corrosion caused by differential aeration. If you dig shallower, you’ll likely miss the active interface; digging deeper places you in soil with less air exposure, where the corrosion you’re looking for is less representative of soil-to-air conditions and it adds unnecessary risk and effort. That six-to-twelve inch depth is the appropriate range.

Corrosion at the soil–air boundary is driven by moisture and oxygen exchange right near the ground surface. Digging to about six to twelve inches below grade reliably exposes the pipe at this interface, so you can actually see coating damage and corrosion caused by differential aeration. If you dig shallower, you’ll likely miss the active interface; digging deeper places you in soil with less air exposure, where the corrosion you’re looking for is less representative of soil-to-air conditions and it adds unnecessary risk and effort. That six-to-twelve inch depth is the appropriate range.