| 摘要 |
PROBLEM TO BE SOLVED: To provide an environment-friendly rainwater storage tank using waste material, having inexpensive building cost and capable of maintaining sufficiently high strength. SOLUTION: A water storage tank 10 is formed by laying a waterproof sheet 90 in a hole 80 provided in the ground, and longitudinally and transversely arranging and upwardly stacking a plurality of water storage boxes 20 made of agricultural containers with their bottom faces 28 facing upward. A rainwater inputting means of inputting rainwater and a rainwater discharging means of discharging rainwater accumulated in the water storage tank 10 are connected with the water storage tank 10.
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