Which depth is allowed for groundwater monitoring as the sole release-detection method?

Which depth is allowed for groundwater monitoring as the sole release-detection method?

• A. 15 feet
• B. 20 feet
• C. 25 feet
• D. 30 feet

Answer: (B)

Groundwater monitoring as the sole release-detection method relies on wells that intercept the groundwater where a leak would form a detectable plume. To be effective and practical, the groundwater depth must be limited so the monitoring wells actually sample the saturated zone in a timely way. The allowed limit is 20 feet. This means groundwater can serve as the only detection method when the water table is 20 feet or less below the surface. If the groundwater is deeper than 20 feet, relying on groundwater monitoring alone isn’t considered sufficient, and additional release-detection methods would be required.

Groundwater monitoring as the sole release-detection method relies on wells that intercept the groundwater where a leak would form a detectable plume. To be effective and practical, the groundwater depth must be limited so the monitoring wells actually sample the saturated zone in a timely way. The allowed limit is 20 feet. This means groundwater can serve as the only detection method when the water table is 20 feet or less below the surface. If the groundwater is deeper than 20 feet, relying on groundwater monitoring alone isn’t considered sufficient, and additional release-detection methods would be required.