A water tank is to be constructed on the soil deposit shown in the figure below. A circular footing of diameter $3$ m and depth of embedment $1$ m has been designed to support the tank. The total vertical load to be taken by the footing is $1500$ kN. Assume the unit weight of water as $10 \: kN/m^3$ and the load dispersion pattern as $2V:1H$. The expected settlement of the tank due to primary consolidation of the clay layer is _________ mm.