Construction of a new building founded on a clayey soil was completed in January $2010$. In January $2014$, the average consolidation settlement of the foundation in clay was recorded as $10 \: mm$. The ultimate consolidation settlement was estimated in design as $40 \: mm$ Considering double drainage to occur at the clayey soil site, the expected consolidation settlement in January $2019$( in mm, round off to the nearest integer) will be _______