The presence of blue clay can be a sign of low permeability and limited groundwater, as it typically forms in anaerobic conditions where water does not easily flow. However, the absence of groundwater cannot be conclusively determined based solely on the presence of blue clay without considering other local geological factors.

No, blue clay is not necessarily a sign of no groundwater. While blue clay can indicate low permeability, which restricts the flow of groundwater, it doesn't mean groundwater is absent. Groundwater can still be present above, below, or within fractures in the clay layer, depending on the local geology.