Abstract: A land fill and method of containing solid wastes and/or waste fluids comprises placing the waste and/or waste fluids, either enclosed in a container, free flowing, solidified or treated, in a preformed cavity or pit that is excavated in a naturally occurring deposit of bentonite clay located adjacent or beneath the surface of the earth. The waste and/or waste fluid is of a type that will not pass through a bentonite layer that is left in its natural place after excavation thereby forming a natural liner or bottom wall of the excavated cavity. After the cavity or pit has been substantially filled with waste material, an overlayer of water-swellable bentonite may be provided on top of the mass of waste material and joining the liner wall around the outer peripheral edge to permanently enclose and seal-off the waste material, or the upper surface of the waste filled pit may be left uncovered.