<< Click to Display Table of Contents >> Navigation:  Appendix A Examples > Example 5: Hydraulic Trap - Finite Mass Source > Description

This example illustrates the use of the program for the case where there is a hydraulic trap (i.e., flow is into the landfill). The parameters are essentially the same as in Case 4, (where there was a finite mass source with a leachate collection system and a fixed outflow base) except that the Darcy velocity has been changed and the base aquifer is now assumed to be only 1 m thick with a porosity of 0.35 and is underlain by a low permeability layer. We also now choose to ignore the width of the landfill and take W = 1 m. This is the same as modeling a 1 m strip through the landfill. This width, W, has no effect on the results.

 

The calculation and values for the Reference Height of Leachate is the same as in Case 4. Again it is assumed that the average infiltration through the cover, (qo) is 0.3 m/a. For this example the Darcy velocity (va) into the base of the landfill is assumed to be -0.001 m/a. The negative value for the Darcy velocity implies that the flow is upward. Neglecting the small volume of groundwater collected the average Volume of Leachate Collected (Qc) is:

 

Qc = qo = 0.3 m/a

 

In this example the inflow in the aquifer at the up gradient edge of the landfill will be 4 m/a and the outflow at the down gradient edge (vb) is then:

 

vb = vb(in) + va*L/h = 4 - 200*0.001 = 3.8 m/a

 

The following parameters are assumed for the example: