Several drums of radioactive waste leaked into a confined aquifer which has a uniform depth of 10 m. The longitudinal, transverse and vertical dispersivities are 1.0m, 0.1m and 0.01m, respectively. The drums leak slowly and can be assumed to constitute a continuous source of 1500 g/L Sr-90 and 500 g/l Cs-137. The average seepage velocity is 20 cm/day. Sr-90 has a half life of 28 years and Cs-137 has a half life of 33 years. A river is located 400m downgradient from the drums. Calculate the time it will take for the Sr-90 and Cs-137 to reach the river and the maximum concentration at the riverbank just before the river