A geotechnical barrier includes a first barrier layer; a second barrier layer overlying the first barrier layer and spaced therefrom, the first and second barrier layers defining, at least in part, a fluid passageway having an inlet and an outlet; and fluid displacement means for displacing a fluid through said fluid passageway from the inlet to the outlet. The invention extends to method for constructing and operating a geotechnical barrier and to a geosynthetic barrier and a geocomposite geosynthetic barrier.