A surface impoundment containing cyanide leaches into a groundwater system that behaves as a

one$-$dimensional aquifer with a hydraulic conductivity of $10\frac{m}{?}$ day, effective porosity of $30\%,$

and hydraulic gradient of $0\mathrm{.}06\frac{m}{m}.$ If the initial concentration of cyanide is $150m\frac{g}{L}$ with a

longitudinal dispersion coefficient $(D_x)$ of $2\mathrm{.}1\frac{m^2}{?}$ day, and sorption and transformation

processes are negligible, determine the time required for the concentration to reach $1m\frac{g}{L}$ in

samples collected from monitoring wells at $300m$ and $1500m$ away from the edge of the

impoundment.

$(8$ pts $)$