PURPOSE: To effectively drain water as well as to recover pipes easily by a method in which plural pipes with water conveyance holes are set and connected in a trench, while chips of rubber, etc., are laid on the pipes, and they are covered with surface soil.

CONSTITUTION: Plural pipes 3 with water conveyance holes 5 are set and connected in a trench 2 excavated in the ground to be improved, rubber or plastic chips 9 are laid in great amounts on the upside 3a side of the pipes 3, and surface soil 10 is covered on the upsides of them to bury the pipes 3. By this, water A in the ground 1 to be improved enters through the apertures between the chips 9 from the ground 11 into the water conveyance holes 5 and then flows out in a given direction on the bottoms 3b of the pipes 3. Thus, since the chips 9 prevent the blocking of the water conveyance holes 5 and apertures are formed among the chips, the draining of water can be assured for a long period of time.