Iwamizawa City, which is located at lat. 43 deg N. and long. 141 deg E., on Hokkaido Island, in the northern part of Japan, experiences heavy snowfall during winter. Every year, the City disposes 610,000 tons of snow collected from its roads and spends 573 million yen for snow removal and 48 million yen for maintenance of the snow dumping sites. However, these dumping sites have, at present, almost reached the limit of their capacities. It is for this reason that snow melting and disposal with treated wastewater was planned. In planning the equalization tank at Nankoen Wastewater Treatment Plant (NWTP), the City intended to use the tank for snow melting during winter. As there were no available data for designing such a tank, experiments were conducted to generate data necessary for designing the snow melting tank. The full-scale tank was constructed based on findings and results of the series of experiments. Results of operation show stable snow disposal and cost reduction for snow removal.