Under what condition can ground rods be exempt from the minimum depth requirement?

Ground rods can be exempt from the minimum depth requirement under conditions of shallow soil. In situations where the soil is not deep enough to accommodate the standard depth for grounding electrodes, local codes or standards allow for this exemption. This is particularly relevant in areas where geological conditions limit soil depth, making it impractical or impossible to install ground rods to the full required depth.

The exemption acknowledges that effective grounding can still be achieved even when ground rods are shallower than the typical standard, as long as they are driven into soil that provides adequate conductivity. This flexibility is important to ensure that grounding systems can still function effectively in diverse environmental conditions.

The other options do not typically provide grounds for exemption under established grounding practices or codes. High water tables and residential structures do not inherently justify deviations from the grounding depth requirements as they relate more to specific site conditions and not soil depth itself.