PURPOSE: To provide a method for building a treatment plant for waste having an effect of protecting the impervious sheets in the treatment plant against UV rays and the external impact of the chemical waste, medicinal liquids, large-sized refuse, etc.z by the final waste emitted from waste incineration furnaces.

CONSTITUTION: A recessed part 2 for the treatment plant having an inverted truncated pyramid shape is formed on the ground surface. The impervious sheets are laid atop the base 2A, front and rear wall surfaces 2B, 2C, right and left wall surfaces 2D, 2E of this,recessed part 2 for the treatment plant. The impervious sheets 3 laid on the inside surfaces of the recessed part 2 for the treatment plant are closely connected and spread by using hook-and-loop fasteners atop the front and rear wall surfaces 2B, 2C and right and left wall surfaces 2D, 2E of the sheets in the parallel state of the mats for side faces. Earth and sand are spread all over the front surfaces of the base 2A.