Question $3.(25$ pts$)$

In a $1500mm$ diameter sewer system with $0\mathrm{.}0008$ slope, an overflow structure is going to be built as shown in the figure below. The wastewater treatment plant is in the downstream of this pipe and has a capacity of $145000\frac{m^3}{d}.$ To prevent any flooding at the treatment plant, the overflow structure shown in the figure below is constructed to divert the excess flow into underground storage tanks where it will be pumped to treatment plant later during dry weather conditions. Calculate the height of the weir so that the flow over $145000\frac{m^3}{?}$ day can be diverted into storage tanks. The Manning's roughness coefficient of the pipe is $n=0\mathrm{.}013.$