An apparatus includes a controllable contaminant-extraction system configured to, at least in part, extract an extractable contaminant from a contaminant plume positioned in the soil via an extraction conduit extending in the contaminant plume. A control assembly is configured to control operation of the controllable contaminant-extraction system in such a way that the controllable contaminant-extraction system extracts the extractable contaminant via the extraction conduit by randomly changing, at least in part, a flow rate of the extractable contaminant that is extracted from the contaminant plume.