Leachate Migration

[owillis28]

Problem:

A municipal landfill utilizes a compacted 1.08 m thick clay liner that has a hydraulic conductivity of 1 x 10-7 cm/sec. If the depth of the leachate above the clay liner is 30 cm and the porosity of the clay is 55%, the time (years) required for the leachate to migrate through the liner is most nearly:

A. 15

B. 17

C. 25

D. 27

owillis

 

[Guest]

A few key points to help you work through this problem:

1. The standing height of the leachate (30 cm) is ASSUMED to be constant;

2. Application of the darcy seepage flow (velocity) equation is the governing equation vs = ki/ne; IMPORTANT CONCEPT

3. Assume the given porosity is the EFFECTIVE porosity (ne);

4. The hydraulic gradient (i) = change in head divided by length of pathway;

5. The change in head, for this problem, would represent the total head. The total head = height of leachate + liner thickness; IMPORTANT CONCEPT

6. The length of the pathway will simply be the liner thickness; and

7. In order to find time - use the simple time = distance/velocity relationship

Try using those tips and tell me what you come up with ...

JR