Appendix A Examples > Example 6: Fractured Layer and Sorption

This example illustrates the use of the program for the case where one of the layers are fractured and there is and sorption of the contaminant species. The “barrier” consists of a 1 m thick compacted clay layer overlying a 3 m thick fractured till. A reactive species (i.e., one that will sorb on to the clay) is modelled in this case. The same finite mass source and leachate collection system is used as in the previous examples. A Darcy velocity (va) of 0.02 m/a through the deposit and an infiltration through the cover (qo) of 0.3 m/a are assumed. The Volume of Leachate Collected (Qc) is then given by:

Qc = qo - va = 0.3 - 0.02 = 0.28 m/a

As in the previous examples the inflow in the aquifer at the up gradient edge of the landfill is 4 m/a. The outflow (vb) at the down gradient edge of the landfill is then:

vb = 4 + 200*0.02 = 8 m/a

The following parameters are defined for this example:

Property	Symbol	Value	Units
Darcy Velocity	va	0.02	m/a
Diffusion Coefficient	D	0.01	m2/a
Distribution Coefficient	Kd	1.5	cm3/g
Soil Porosity	n	0.4	-
Dry Density		2	g/cm3
Soil Liner Thickness	HL	1	m
Number of Sub-layers		1	-
Fractured Till Thickness	HT	3	m
Number of Sub-layers		1	-
Fracture spacing in x direction	2H1	1	m
Fracture opening in x	2h1	10	µm
Fracture spacing in y direction	2H2	1	m
Fracture opening in y	2h2	10	µm
Dispersion along fractures	Df	0.06	m2/a
Fracture Distribution Coefficient	Kf	0	cm3/g
Matrix Diffusion Coefficient	Dm	0.01	m2/a
Matrix Distribution Coefficient	Km	1.5	cm3/g
Matrix Porosity	nm	0.4	-
Dry Density of Matrix		2	g/cm3
Source Concentration	co	1000	mg/L
Rate of Increase in co	cr	0	mg/L/a
Ref. Height of Leachate	Hr	7.5	m
Volume Collected	Qc	0.28	m/a
Landfill Length	L	200	m
Landfill Width	W	1	m
Thickness of Aquifer	h	1	m
Porosity of Aquifer	nb	0.35
Base Outflow Velocity	vb	8	m/a
Lower and Upper Time Limits		20, 300	a

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