The relationships between turbidity and operating conditions of pump dredger are investigated by field test. This investigation is conducted in Matsuyama area of Kanda Port under the construction of anchorage, and the dredger is supplied with the power of 2,250 P.S. by diesel electric system.
　Among the operating conditions, dredging thickness and swing speed are varied, and the influence of them on turbidity is investigated. Suspended solids concentration (abbreviated usually to SS) is used as the representation of turbidity. Water samplings for SS are carried out at four point at the same time when the cutter reaches the central point of its swing.
　In order to estimate the dredging capacity, mud mixture ratio in a floating pipe, flow rate, and vacuum pressure of the dredging pump are measured.
　The turbidity near the cutter depends on effective suction ratio which is defined by the ratio of the amount of soil sucked up by the pump to that excavated by the cutter and its swing. Turbidity is not detected at the boats located from 30m to 180m far from the cutter on the condition that tidal current is below 0.02m/s in many cases.