A contaminated waste disposal site is contained by constructing a slurry wall keyed into an aquitard as shown below. The contained area is roughly circular with radius R and is covered with a clay cap which prevents infiltration of precipitation. For the parameters show below, find:

1. The steady-state water level inside the wall
2. The total steady flow leaking through the slurry wall
3. The time required for the average concentration of a nonreactive solute inside the contained area to be reduced to 5% of its original value.

Note: the water in the phreatic aquifer outside the slurry wall is originally not contaminated. For the concentration calculation, you may assume that the flow is a steady one corresponding to the ultimate steady state found in steps 1 and 2. 

Given information:

• porosity of waste material   n = 0.25
• aquitard conductivity          K' = 2x10^-3 ft/day
• aquitard thickness               b' = 10 ft
• slurry wall conductivity      K_w = 2x10^-3 ft/day
• slurry wall thickness           b_w = 3 ft
• phreatic aquifer head           h_p  = 30 ft
• confined aquifer head          h_c = 10 ft
• radius of contained area      R = 500 ft