PROBLEM $15$: A proposed pulp processing plant is expected to emit $\frac{1}{2}$ ton per day of hydrogen sulfide from a single stack. The company property extends a minimum of $1500$ meters from the proposed location. The nearest receptor

is a small town of $500$ inhabitants $1700$ meters northeast of the plant. Plant managers have decided that it is desirable to maintain concentrations below $20ppb($parts per billion by volume$),$ or approximately $2\mathrm{.}9{10}^{-5}g{m}^{-3},$

for any period greater than $30$ minutes. Wind

direction frequencies indicate that winds blow

from the proposed location toward this town

between $10$ and $15$ per cent of the time. What

height stack should be erected? It is assumed

that a design wind speed of $2mse{c}^{-1}$ will be

sufficient, since the effective stack rise will be

quite great with winds less than $2mse{c}^{-1}.$

Other than this stipulation, assume that the

physical stack height and effective stack height

are the same, to incorporate a slight safety

factor.