A method for lining an existing waste disposal site having a waste level includes, for example: installing perimeter barrier walls about the site and interior barrier walls within the perimeter barrier walls to define cells; transferring waste, such as for example ash, from one of the cells to one or more other cells to form an empty cell with a layer of contaminated material at the bottom of the empty cell; removing the layer of contaminated material from the empty cell to form a clean cell with a noncontaminated bottom layer; installing a barrier liner layer in the clean cell to form a lined cell; and transferring waste from other cells into the lined cell.