A mathematical model is developed for transport of radionuclides in the system consisting of water–hot particles in bottom deposits–particles of bottom deposits. This model is used to study the consequences of the radiation accident in bukhta Chazhma in 1985. The escape of 60Co into the bukhta water from bottom deposits is estimated. Although the fraction of 60Co escaping is small (about 10−5), estimates show that its concentration in water can reach hundreds Bq/m3. The time dependence of the 60Co concentration in the upper layer of bottom deposits is estimated.