effect of perched water conditions in msw landfills
TRANSCRIPT
![Page 1: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/1.jpg)
Effect of Perched Water Conditions in MSW Landfills:
Considerations for Landfill Operators
Timothy Townsend and Pradeep JainDepartment of Environmental Engineering
University of Florida
2005 SWANA Landfill SymposiumBolder, Colorado
![Page 2: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/2.jpg)
Motivation
• At last year’s landfill symposium, several presentations and audience comments described the issue of saturated waste layers in the deeper parts of landfills.
• The presence and cause of these saturated layers can be interpreted differently.
• The question that we asked: “what should one expect?”
![Page 3: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/3.jpg)
LCRSLiner
MSW
Consider a MSW Landfill
![Page 4: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/4.jpg)
Install Gas Wells
![Page 5: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/5.jpg)
LCRSLiner
MSW
Consider a MSW Landfill
![Page 6: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/6.jpg)
LCRSLiner
MSW
Landfill GasWell
![Page 7: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/7.jpg)
LCRSLiner
Landfill GasWell
WaterSurface
![Page 8: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/8.jpg)
Implications of Perched Water
• Problems with gas recovery?
• Slope stability concerns?
• Leachate collection system problems?
• Future side slope seepage issues?
![Page 9: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/9.jpg)
Landfill gas well equipped with liquidpumping system
![Page 10: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/10.jpg)
Pump repairand maintenance
![Page 11: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/11.jpg)
LCRSLiner
Landfill GasWellSlope stability
concerns
![Page 12: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/12.jpg)
LCRSLiner
Landfill GasWellSlope stability
concerns
![Page 13: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/13.jpg)
LCRSLiner
Landfill GasWellSlope stability
concerns
![Page 14: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/14.jpg)
The implications of the perched liquids depend on their true nature
within the landfill
![Page 15: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/15.jpg)
LCRSLiner
Landfill GasWell
WaterSurface
![Page 16: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/16.jpg)
LCRSLiner
Landfill GasWell
Phreaticsurface
![Page 17: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/17.jpg)
LCRSLiner
Landfill GasWell
![Page 18: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/18.jpg)
LCRSLiner
Landfill GasWellSlope stability
concerns
![Page 19: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/19.jpg)
LCRSLiner
Landfill GasWellSlope stability
concerns
![Page 20: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/20.jpg)
LCRSLiner
Landfill GasWellSlope stability
concerns
![Page 21: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/21.jpg)
Let’s examinethe scenario where only
waste around the well is saturated
Some source of water is added to the well at a rate greater that it can drain out. Possible sources:
• Gas condensate• Perched zones of
leachate in the landfill• Short circuiting from
liquids addition
![Page 22: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/22.jpg)
Gas Well
![Page 23: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/23.jpg)
Soil Layer
PerchedLiquids
![Page 24: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/24.jpg)
![Page 25: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/25.jpg)
Flow1 Flow2 Flow3
Vertical Injection Wells at New River Regional Landfill
![Page 26: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/26.jpg)
![Page 27: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/27.jpg)
Modified Version of Richard’s Equation
( )t
St
C
kz
kz
Krr
kKr
kr
K
s
zr
r
∂∂
+∂
∂=
=
+
∂∂
∂∂
+∂∂
+
∂∂
∂∂
ψψψ
ψψψ
Richard’s equation was solvedusing a USGS program called
SUTRA
![Page 28: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/28.jpg)
r0 5 10 15 20
z
0
5
10
15
20
S=1
S=0.2
![Page 29: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/29.jpg)
r0 5 10 15 20
z
0
5
10
15
20
ψ=0
ψ=2 m
ψ=4 m
![Page 30: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/30.jpg)
r (ft)0.0 1.0 2.0 3.0 4.0
z (ft
)
0
10
20
30
0 ft1 ft2 ft3 ft4 ft5 ft
Simulation Parameters
K = 10-5 cm/sec
Q = 17 gallons/day
Duration of Moisture Addition = 10 days
Head in the well ~ 8 ft
![Page 31: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/31.jpg)
LCRSLiner
Landfill GasWell
Phreaticsurface
![Page 32: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/32.jpg)
• If the liquids are added to the landfill at a rate greater than the hydraulic conductivity, saturated conditions will result
Let’s examinethe scenario where saturated conditions will develop in the
landfill even if barrier layers are not present
![Page 33: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/33.jpg)
Consider a Liquids Infiltration Pond
• The waste underneath the pond will become saturated
• In the absence of cover soil layers, a saturated zone will extend to the leachate collection system
![Page 34: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/34.jpg)
LCRSLiner
MSW
Consider a MSW Landfill with an Infiltration Pond
![Page 35: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/35.jpg)
LCRSLiner
MSW
Consider a MSW Landfill with an Infiltration Pond
![Page 36: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/36.jpg)
LCRSLiner
Consider a MSW Landfill with an Infiltration Pond
h
d
ddhi +
=
![Page 37: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/37.jpg)
LCRSLiner
MSW
Consider a MSW Landfill with an Infiltration Pond
![Page 38: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/38.jpg)
LCRSLiner
MSW
Consider a MSW Landfill with an Infiltration Pond
![Page 39: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/39.jpg)
LCRSLiner
MSW
Consider a MSW Landfill with an Infiltration Pond
WaterLevel
![Page 40: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/40.jpg)
Can saturated conditions develop if the liquids are added at a rate less than the permeability of the waste?
• Yes, if the permeability of the waste is reduced with depth
DecreasingPermeability
![Page 41: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/41.jpg)
Col 21 vs Col 22
Density (t/m3)
0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
Hyd
raul
ic C
ondu
ctiv
ity (m
/sec
)
10-8
10-7
10-6
10-5
10-4
10-3
At ~1400 pcyK = 8x10-5 cm/sec
![Page 42: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/42.jpg)
Air permeability of waste at NRRL at different depths
Air Permeability, k (X10-12 m2)
<0.1
0.1-
2.5
2.5-
5.0
5.0-
7.5
7.5-
10.0
10.0
-12.
5
12.5
-15.
0
15.0
-17.
5
17.5
-20.
0
20.0
-22.
5
22.5
-25.
0
>25.
0
Num
ber o
f Loc
atio
ns
0
3
6
9
12
15
![Page 43: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/43.jpg)
Air Permeability, k (X10-12 m2)
<0.1
0.1-
2.5
2.5-
5.0
5.0-
7.5
7.5-
10.0
10.0
-12.
5
12.5
-15.
0
15.0
-17.
5
17.5
-20.
0
20.0
-22.
5
22.5
-25.
0
>25.
0
Num
ber o
f Loc
atio
ns
0
3
6
9
12
15
Air permeability of waste at NRRL at different depths
![Page 44: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/44.jpg)
Air Permeability, k (X10-12 m2)
<0.1
0.1-
2.5
2.5-
5.0
5.0-
7.5
7.5-
10.0
10.0
-12.
5
12.5
-15.
0
15.0
-17.
5
17.5
-20.
0
20.0
-22.
5
22.5
-25.
0
>25.
0
Num
ber o
f Loc
atio
ns
0
3
6
9
12
15
Air permeability of waste at NRRL at different depths
![Page 45: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/45.jpg)
Bottom Liner
Compacted MSW
Leachate Collection System
27 Gpd K=10-4 cm/s
K=5X10-5 cm/s
60 ft
![Page 46: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/46.jpg)
Pressure (ft of w.c.)
-8 -6 -4 -2 0 2 4 6 8
Dep
th (f
t)
0
10
20
30
40
50
60
![Page 47: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/47.jpg)
Simulation Parameters
Decreasing K = 10-5
cm/sec (top) to 5X10-6
cm/sec (bottom at 60 ft deep)
Q = 8.5 gallons/day
Duration of Moisture Addition = 10 days
Head in the well ~ 5 ft
r (ft)0.0 1.0 2.0 3.0 4.0
z (ft
)
0
10
20
30
0 ft1 ft2 ft3 ft4 ft
![Page 48: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/48.jpg)
Review
• The existence of standing liquids in gas wells in landfills does not necessarily result from a phreatic liquid surface in the landfill.
• Liquids added to wells as a result of perched layers in the landfill, gas condensate or other sources can result in relatively large depths of water in the well.
![Page 49: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/49.jpg)
Review
• The decreasing permeability of landfilled waste with depth should have impact.
• Saturated waste conditions may be present, but the pressure of this water may not be accurately reflected by the depth of water that would be measured if a well was installed.
• At large liquid addition rates, saturated conditions in deeper layers may develop.
![Page 50: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/50.jpg)
Implications
• The presence of liquids in gas wells in “dry” landfills should not automatically assumed to represent a phreatic surface.
• In “wet” landfills, the liquid levels in wells may result from both situations.
• When evaluating slope stability, careful thought must be given to the pressures that truly occur.
• Leachate collection systems need to be designed and operated correctly.
![Page 51: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/51.jpg)
New Experiment in FloridaBury piezometers in waste
vertical well and horizontal trench
![Page 52: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/52.jpg)
25’ Between Wells
Well #1 Well #2
10’
VW Piezometer Well
Injection Wells
5’
Current Bioreactor
![Page 53: Effect of Perched Water Conditions in MSW Landfills](https://reader031.vdocuments.mx/reader031/viewer/2022020703/61fb40532e268c58cd5bf4c0/html5/thumbnails/53.jpg)
MSW
10’
5’
20’
30’
40’
VW piezometers
Data Station
Injection Well #1
Cover Soil
10’
20’
35’
Injection Well #2