Abstract: A method for the containment of liquid-containing waste materials, such as drilling residues, in an earthen reservoir is described. The method comprises providing an in-ground reservoir opening upwardly to the surface of the ground and a sloping in-ground drainage area abutting one side of the reservoir, the bottom of the drain area being below the level to which the reservoir is filled. The reservoir and drainage area are lined with flexible liquid-impervious liners having extended sides. The extended sides of the reservoir lining are drawn, in part, over waste material in the reservoir leaving a center area of waste material uncovered with overlapped reservoir liner. The drainage area is filled with ballast material to provide a porous bed and is provided at its low end with a stand-pipe which extends from near the bottom of the drainage area to above the surface of the ground.