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A Numerical Study of Barometric Pumping. Jeff Sondrup AgE 588 Fluid Mechanics of Porous Materials April 11, 2001. Presentation Outline. Introduction Gas Transport & Barometric Pumping Model Description Model Results Conclusions. Subsurface Disposal Area, INEEL. - PowerPoint PPT Presentation
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A Numerical Study of Barometric Pumping
Jeff Sondrup
AgE 588
Fluid Mechanics of Porous Materials
April 11, 2001
Presentation Outline
• Introduction
• Gas Transport & Barometric Pumping
• Model Description
• Model Results
• Conclusions
Subsurface Disposal Area, INEEL
VOC Background at the SDA
• VOCs first discovered in GW near SDA in 1987• Soil gas survey confirmed SDA pits and trenches were a VOC source• Inventory search indicated sludges containing VOCs from Rocky Flats
buried in SDA (1966-70)
• Primarily carbon tetrachloride (CCl4) with TCE, PCE, and TCA
• Vadose zone vapor sampling indicates a large plume• GW concentrations ND to slightly above MCL• Modeling estimates GW concentrations to peak decades in the future at
several times MCL• ROD signed in 1994, Soil Vapor Extraction (SVE) preferred alternative• Five extraction wells began operating 1996, removed ~75,000 lbs
TVOCs, ~48,000 lbs CCl4
Gas Transport Mechanismsin the Vadose Zone
• Advection (contaminants travel with the bulk movement of air)
– Natural: water displacement, barometric pressure changes, density
– Induced: drilling, soil vapor extraction (SVE)
• Diffusion (random motion of molecules)
• Sorption (contaminants adhere to the rock/soil)
• Vapor-Liquid Partitioning (contaminants move into and out of air-water)
Barometric Pumping
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
SedimentaryInterbed
SedimentaryInterbed
VadoseZone580 ft.
Region ofFractured
Basalt
Top of Snake River Pla in Aquifer
App
roxi
ma
te V
ertic
al S
cal
e (f
eet
)
0
50
100
150
200
250
300
350
400
450
500
550
600
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
RepresentativeDisposal Pits
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
2
Time
Pre
ssur
e
23
3
The sediment or lower permeabilitylayers dampen the signal and causea phase shift (lag) in the response.
Barometric Pressure Data
8 30
8 35
8 40
8 45
8 50
8 55
8 60
1 6 -M a r 2 1 -M a r 2 6 -M a r 3 1 -M a r 5 -A p r 10 -A p r 1 5 -A p r
Bar
omet
ric P
ress
ure
(mb) Square Wave
Approximation
Data
SinusoidalApproximation
Mean Pressure
Date
Model Geometry & Grid
0 20 40 60 80 1000Distance (m)
0
10
20
30
40
50
60
70
0
Dep
th (
m)
VOC Source
Basalt
Sediment
Hydraulic Properties of Fractured Basalt and Sediment
0.1
1
10
100
1000
10000
0 0.2 0.4 0.6 0.8 1
Water Saturation
Pre
ssu
re (
-kP
a)
Fractured BasaltSediment
Property Basalt Sediment
Permeability 9000 mD (horz)300 mD (vert)
4 mD
Porosity 0.05 0.5Residual
Water Sat.0.02 0.194
(van G) 10 m-1 1.60 m-1
n (van G) 2.5 1.70
Properties ofCarbon Tetrachloride
Property Value Source
Air DiffusionCoefficient
0.72 m2/d Lugg et al. (1968)
Water DiffusionCoefficient
7.2E-05 m2/d Water diffusion coefficients are typically fourorders of magnitude less than air diffusioncoefficients (Perry and Chilton, 1973).
Organic CarbonPartition Coefficient
439 mL/g U.S. EPA (1990)
Henry's Constant 0.750 Non-dimensional value at 15 C as reported byGossett (1987).
Liquid Density 1584 kg/m3 Cohen and Mercer (1993)
Liquid Viscosity 1.0 cP Pankow and Cherry (1996)
Gas Viscosity 1.8E-5 Ns/m2 Viscosity of air at 20 C
Vapor Pressure 9.7 kPa Value at 15 C reported by Pankow and Cherry(1996)
Critical Pressure 4560 kPa CRC (1987)
Critical Temperature 557 K CRC (1987)
Barometric Pressure Data
8 30
8 35
8 40
8 45
8 50
8 55
8 60
1 6 -M a r 2 1 -M a r 2 6 -M a r 3 1 -M a r 5 -A p r 10 -A p r 1 5 -A p r
Bar
omet
ric P
ress
ure
(mb) Square Wave
Approximation
Data
SinusoidalApproximation
Mean Pressure
Date
Barometric PressureSine Wave Approximation
-1.5
-0.5
0.5
1.5
0 5 10 15 20 25 30
Time (days)
DP
(kP
a)
Base Case Simulation(No Barometric Pumping)
0 10 20 30 40 50 60 70 80 90 100Horizontal Distance (m)
010
20
30
40
50
6070
0
Dep
th (m
)
6 months
1000 100 10
Barometric Pumping(Square Wave Approximation Dt=1 day)
0 10 20 30 40 50 60 70 80 90 100
010
20
30
40
50
6070
0
Dep
th (
m)
6 months
1000 100 10
Barometric Pumping(Square Wave Approximation Dt=10 day)
0 10 20 30 40 50 60 70 80 90 100
010
20
30
40
50
6070
0
Horizontal Distance (m)
Dep
th (m
)
6 months
1000 100 10
Barometric Pumping(Sine Wave Approximation Dt=1 day)
0 10 20 30 40 50 60 70 80 90 100
010
20
30
40
50
6070
0
Horizontal Distance (m)
Dep
th (m
)
6 months
1000 100 10
CCl4 Vertical Profile (1 year)0
10
20
30
40
50
60
700 500 1000 1500 2000
CCl Vapor Concentration (ppmv)4
Dep
th(m
)
Base Case (no barometric pumping)
Baro Pumping (sine wave, t=1 day)D
Baro Pumping (sqr wave, t=1 day)D
1 year
CCl4 Vertical Profile (5 years)0
10
20
30
40
50
60
700 10 20 30 40 50
CCl Vapor Concentration (ppm v)4
Dep
th(m
)
Base Case (no barometric pumping)
Baro Pumping (sine wave, t=1 day)D
Baro Pumping (sqr wave, t=1 day)D
5 years
CCl4 Mass Remaining in VZ
0.01
0.1
1
1 2 3 4 5
Time (years)
CC
l M
ass
in V
ado
se Z
on
e (k
g)
4
Base Case (no barometric pumping)
Barometric Pumping (sine wave, t=1 day)D
Barometric Pumping (square wave, t=10 days)D
Barometric Pumping (square wave, t=1 day)D
CCl4 Mass Accounting(Barometric Pumping, Square Wave, Dt=1 day)
CC
l M
ass
(kg
)4
0.001
0.010
0.100
1.000
0 1 2 3 4 5
Time (years)
Total Mass
Mass in Vadose Zone
Diffusive Mass to Atmosphere
Advective Mass to Atmosphere
Mass to Aquifer
Conclusions
• Time step important when simulating BP
• Square wave approximation is reasonable if pressure patterns predictable and repeatable
• BP impact small but can be important
• Impact is site and event specific (depends on contaminant, location, pressure patterns, subsurface)
• Diffusion is the dominant mechanism
• BP important for passive soil venting (gas extraction)
