To reduce a cost by reusing a material without generating industrial waste when lowering an underground water level with a ground water level lowering device.
The ground water level lowering device 1 exposing an upper end 3a on ground, enforcedly discharging ground water flowed in the inside of well casing pipes 2 and 3 embedded in ground with a pumping means to the ground and lowering the ground water level, comprises an outer cylindrical pipe 11 connecting a filter pipe 6 to a lower end 2b of the well casing pipe 2 and allowing the filter pipe 6 to flow in the ground water in the inside; an inner cylindrical pipe 12 having a second strainer part 12a provided from an inner wall face 11c of the outer cylindrical pipe 11 to the inside of a radial direction with a gap and flowing in the ground water to the inside; and a filter 13 held in the gap and filtering the ground water.
Tadashi Takahashi
Takashi Watanabe
Masakazu Aoyama
Suzuki Mitsuyoshi
Kazuya Nishi
Yasuhiko Murayama