The special ejector pump system is able to pick up the sediment from the bottom of reservoir by means of the pressure gradient generated by jet water. In this system, the maximum expected size of gravel which can be transported is approximately 150 mm. The field tests on this newly developed system was very successful as approximately 3,500 m³ sediment was dredged by special ejector pump from different depths in the reservoir, 3 to 15 m deep; and then the sediment relocated to the disposal site, 400 m upstream from the suction point, by floating transportation pipeline. The sediment transportation rate was equal to approximately 70 m³/h.

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One of the roles of filter zone of rock fill dam is to prevent core zone material from being flowed out. This function is expressed under the condition that grading relation of core and filter zone material satisfies the Filter law and permeability coefficient of filter zone is from 10 to 100 times of that of core zone. As a result of preliminary examination conducted in advance of filling test at Tono dam locating within administrative area of Chugoku Regional Development Bureau, grading of core and filter zone material satisfied the Filter law but permeability coefficient of filter zone was more than 100 times of that of core zone. Due to this result, the Dirty-Water Test for this filter zone material was conducted to evaluate its availability for filter zone.

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