A process is described for a water efficient, ecologically acceptable collection, delivery and depositing of slag and flyash from thermal power plants fired with pulverized coal. Slag is allowed to fall into a cooling water basin, conveyed to a condenser where it is combined with coarse flyash, te slag-flyash combination is delivered to a mixing space and combined with fine flyash, thereby forming a homogeneous mixture and the mixture is then circulated under specified conditions to achieve comminution to a predetermine value. Comminuted homogeneous mixtures is then measured continuously for properties of viscosity, quantity and pressure parameters. Information on the parameters is fed to a computer for comparison with preset values. The comminuted homogeneous mixture is then deposited in a deposit space. Any cooling water lost in the collecting-delivering and depositing steps is then replaced. A colloidal material may be added to the comminuted homogeneous mixture during the deposition step.