1. Remediation of a Leaking Landfill Site
Problem Set # 4
Remediation of a Leaking Landfill Site
river
3 layers
MODFLOW’s River Package
transient flow
remediation design
municipal water supply well
In layer 3

2. Objectives
Determine the impacts of contamination
from the leaking landfill (shown in light
blue) at the river and the municipal well.
Design a strategy to mitigate the effects
of the contamination.

3. Head Dependent Boundaries
Review from Geology 724
Head Dependent Boundaries
in MODFLOW
Q = C h 
River Package
Drain Package
General Head Boundary (GHB) Package
ET Package

4. River Package Q = C (hR – hijk) where C = (Kv/m) L w
hR = head in the river
hijk is the head at the
node below the river
Q = C (hR – hijk)
where
C = (Kv/m) L w

5. River Package Q = C (hR – hijk) where C = (Kv/m) L w
hR = head in the river
Typically the
width of the
river is smaller
than the width
of the grid cell.
hijk is the head at the
node below the river
Q = C (hR – hijk)
where
C = (Kv/m) L w
Length of the river
within each cell
also may vary.
Areal view of the river

7. Q = C (hR – hijk)
hijk m
RBOT w
Gaining River Cell

8. Q = C (hR – hijk)
RBOT
Losing River Cell

9. Q = C (hR – hijk)
RBOT
Losing River Cell

10. Percolating River Cell
Q = C (hR – RBOT)
RBOT
Percolating River Cell

11. Definitions Riverbed Conductance = (Kv/m) wL Leakance = Kv/m
Resistance = m/Kv
Kv = vertical hydraulic conductivity of riverbed sediments
m = thickness of riverbed sediments
w = width of the river
L = length of the river within the cell

12. Resistance River with sandy bottom = 1 day
Small stream with silty bottom = days
Stream/lake in till = 100 days

13. In PS4, we consider the alternative to “do nothing”
as a remediation strategy. This is called “natural attenuation”.
Recommended groundwater monitoring network for
demonstrating natural attenuation. Source: EPA circular

14. Initial conditions In Part 3A of PS4, We will use I.C. of the type
shown in Figure a.
This is done in the
initial concentrations
window of GWV.
Zheng &
Bennett