By Hydrosimulatics INC  

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      Kw = 2x10-3 ft/day
  • slurry wall thickness           bw = 3 ft
  • phreatic aquifer head           hp  = 30 ft
  • confined aquifer head          hc = 10 ft
  • radius of contained area      R = 500 ft