Transcript Independent Technical Review of Operational Issues at

Research on Engineered
Barrier Technology by
CRESP's Landfill Partnership
Craig H. Benson, PhD, PE, DGE
Wisconsin Distinguished Professor
University of Wisconsin-Madison/CRESP
[email protected]
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On-Site Disposal Facility (OSDF):
aka LLW or MW Landfill
Final
Cover
System
MONITORING
WELLS
W A S T E
S
ES D
C
A
AC RO
Liner
System
Figure courtesy M. Othman, Geosyntec Consultants
Engineering Property
The Challenge – Confident Design
for a Millennium
?
?
As-Built
1
Current Field
Research &
Experience
10
?
Analogs
100
Time (years)
1000
3
Purpose of Landfill Partnership
• Conduct independent applied research to
address landfill technology issues that crosscut the DOE complex.
• Provide forum to discuss regulatory conflicts
and shortcomings, and to recommend
technological solutions.
• Participate in independent technical reviews
related to DOE technologies or sites.
4
Relevance
• OSDFs (landfills) are key step in D&D/restoration
at EM sites; stakeholder concerns regarding
long-term performance impede
acceptance/permitting.
• NAS (2009) identifies existing knowledge on
long-term performance of waste containment
structures as a principle science and technology
gap for EM. Credibility gap for stakeholders.
• LP to provide source terms for EM’s ASCEM
(analogous to CBP).
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Technical Priorities to Build Confidence
1. Develop confidence in the long-term (1000 yr)
performance of OSDF designs.
2. Understanding of degradation mechanisms
affecting containment systems in OSDFs.
3. Understand and quantify how final covers evolve
over the design life of OSDFs.
4. Develop confidence in models used for PAs of
OSDFs and characterize uncertainty in predictions.
5. Create and evaluate monitoring strategies that
build confidence in the performance of OSDFs.
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Approach to Build Technical Confidence
• Understand our existing technology – does it
work as well as we predict?
• Understand how barriers degrade or evolve
over time so that we can make confident longterm predictions.
• Develop reliable methods (e.g., computer
tools) to predict performance in as-built state,
and as barrier degrades.
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1. Understanding our Existing Technology
• State-of-the-art: knowledge base from field
studies of barrier performance.
– Resistive barrier technologies
– Water balance barrier technologies
• State-of-the-art: lessons learned from field
studies of cover soil pedogenesis.
• Leachate source terms for LLW disposal
facilities.
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2. Developing Prediction Methods
• Mechanistic description of radionuclide
sorption and diffusion in barrier systems.
• Assessing methods to measure radionuclide
sorption and diffusion in barrier systems
• Accounting for large-particle effects in soil
water retention.
• Efficacy of transport models for predicting
transport through barrier systems
• Evaluating how input uncertainty/sparseness
affects uncertainty in model predictions.
.
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3. Understanding Barrier Degradation
• Geomembrane degradation & life expectancy
in LLW facilities.
• Degradation of bentonite barriers due to ion
exchange, hydration-exchange kinetics, and
environmental stress (freezing, drying).
• Degradation of bentonite barriers exposed to
concrete surfaces.
• Design strategies that manage degradation &
ensure adequate performance (e.g.,
evolutionary covers, surface treatments).
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Geomembrane Degradation
No credible scientific data for LLW
or MW to draw inference, but
methods from solid waste
literature
Speculative discussion
at Paducah in March ‘11.
Literature suggests
lifespan may be more
than 1000 yr.
No data for conditions in
LLW or MW facilities.
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Durability Tests in Synthetic LLW Leachate
• Three temperatures
(50, 70, & 90 C)
• Three solutions (DI,
LLW, and LLWRad)
• 2 mm HDPE
(ERDF, OSDF).
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Parameters
LLW
Average
Synthetic
Target
TOC (mg/L)
7.73
8
Reduction Potential
(mV)
114.86
120
pH
7.21
Inorganic Macrocomponents (mM/L)
Calcium
3.71
Magnesium
4.49
Sodium
5.27
Potassium
0.38
Sulfate
7.11
Chloride
4.7
Nitrate/Nitrite
1.42
Alkalinity
3.42
Metals (mM/L)
Aluminum
0.022
Arsenic
0.00066
Barium
0.0017
Copper
0.00011
Iron
0.032
Lithium
0.015
Manganese
0.0082
Strontium
0.015
Zinc
0.0003
Radionuclides (ERDF Ave)
Uranium (µg/L)
H-3 (pCi/L)
Tc-99 (pCi/L)
1488
111530
730
7
4
5
5.6
0.5
7.5
5
1.5
3.5
0.03
0.001
0.002
0.0002
0.05
0.02
0.01
0.02
0.0005
1500
120000
800
Geomembrane Incubators
Major Cations in LLW Leachate
1x10
2
(a)
(b)
Concentration (mmol/L)
Ca
1x10
1
1x10
0
1x10
Mg
-1
OSDF
ERDF EMWMF ICDF
All LLW MSW
OSDF
ERDF EMWMF ICDF
All LLW MSW
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Radionuclides: U and Tc
1x10
4
1x10
3
1x10
1x10
(b)
3
Concentration of Tc-99 (pCi/L)
Concentration of Uranium (µg/L)
(a)
2
1x10
1
1x10
0
OSDF
ERDF
EMWMF
ICDF
All LLW
1x10
2
1x10
1
1x10
0
OSDF
ERDF
EMWMF
ICDF
All LLW
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Temporal Behavior: U and Tc
1x10
4
1x10
1x10
1x10
1x10
Concentration of Technetium (pCi/L)
Concentration of Uranium ( µg/L)
(a)
3
2
1
OSDF
ERDF
EMWMF
ICDF
1x10
0
2
4
6
Time (yr)
8
10
12
(b)
1x10
2
1x10
1
1x10
0
3
OSDF
ERDF
EMWMF
ICDF
0
0
2
4
6
8
10
12
Time (yr)
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Temporal Behavior: Sr and Tritium
1x10
3
1x10
6
1x10
1x10
1x10
(d)
Concentration of Tritium (pCi/L)
Concentration of Stronium-90 (pCi/L)
(c)
2
1
0
1x10
5
1x10
4
1x10
3
1x10
2
ERDF
1x10
1
EMWMF
EMWMF
ICDF
1x10
ICDF
-1
1x10
0
1
2
3
4
5
Time (yr)
6
7
8
0
0
2
4
6
8
10
12
Time (yr)
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Coupling Hydrological & Erosion
Control on Covers
631 m
1606 m
452 m
• Used Cheney
Disposal Facility
(Grand Junction,
CO) as base case
• SIBERIA landform
evolution model
(1000 yr simulation)
631 m
Max Elevation = 1606 m
Min Elevation = 1584 m
1584 m
807 m
• SVFLUX variably
saturated flow model
for hydrology.
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Erosion on Rip-Rap Covers
Resistive Cover Soil Profile
305 mm
Cover top layer
150 mm
Bedding layer (Rip-rap only)
610 mm
Frost protection layer
610 mm
Radon barrier
915 mm
Transition layer
Remaining
1000 Year Erosion - Vegetated Riprap Cover
Semi-Arid Climate
Tailings
Rip-rap surface
layer
1m
2m
3m
4m
5m
6m
7m
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Coupling Hydrological & Erosion Control on
Covers: Gravel Admixture Cover
Resistive Cover Soil Profile
305 mm
Cover top layer
150 mm
Bedding layer (Rip-rap only)
610 mm
Frost protection layer
610 mm
Radon barrier
915 mm
Transition layer
Remaining
1000 Year Erosion - Vegetated 40% Gravel Admixture Cover
Semi-Arid Climate
Tailings
Gravel Admixture
Topsoil Surface Layer
2m
4m
6m
8m
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• Gravel admixture
covers have net
release to
atmosphere
200
T y p ic a l
W e tte s t
Flow
Out of
Waste
100
0
• Rip-rap covers
harvest water –
collect and drain into
waste.
Flow
Into
Waste
-1 0 0
R ip - r a p
G r a v e l A d m ix tu r e
T o p s o il
R ip - r a p
G r a v e l A d m ix tu r e
-2 0 0
T o p s o il
E n d - o f- y e a r C u m u la tiv e P e r c o la tio n ( m m )
Hydrological Prediction for Grand Junction, CO
• Similar efficacy for
erosion control!
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Transport Parameters for Barriers
Diffusion and sorption tests for
geomembranes.
Evaluating new geomembrane
with exceptionally low radon
diffusion coefficient.
U p p e r R es e rvoir
M o d e l D C -K D (U R )
M o d e l D C -D (U R )
Lo w e r R e se rvo ir
M o d el D C -K D (L R )
M o d el D C -D (L R )
1 .0
0 .8
0 .8
R ela tiv e C o n c e n tratio n (C /C )
1 .0
L o w e r R e s e rvo ir
M od el D C - K D (L R )
M od el D C - D (L R )
o
o
R e lativ e C o n c e n tra tio n (C /C )
U p p er R es e rvoir
M o de l D C -K D (U R )
M o de l D C -D (U R )
0 .6
0 .4
0 .2
0 .0
(a )
0
20
40
60
T im e (d a y s)
80
100
120
0 .6
0 .4
0 .2
0 .0
(b )
0
20
40
60
T im e (d a y s)
80
100
120
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Transport Prediction for Barriers
152 mm I.D.
Co
Influent bag
Concentration
Effluent bag
Sampling port
Partition into
geomembrane
Cg = C o K g
Leachate
80 mm
Threaded
tie-rod
60 mm
Diffusion through
geomembrane
Geomembrane
Compacted clay liner
Cs
Soil Liner
Upper reservoir
Partition out of
geomembrane`
Cg = C s K g
Ls
Geomembrane
Concentration distribution
30 mm 30 mm
120 mm
Lg
z=0
Sampling
port
z
Sampling port
Glass fiber filter
Co= Leachate Concentration
Cg= VOC Concentration in Geomembrane
Cs= VOC Concentration in Soil Pore Water
Kg= Partition Coefficient of Geomembrane
70 mm
12 mm
70 mm
(a)
Lg= Thickness of Geomembrane
Ls= Thickness of Soil Liner
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Prediction - TCE Transport in Clay Barrier
50
40
Concentration (mg/L)
(c) TCE
Replicate 1 (depth=60mm)
Replicate 2 (depth=60mm)
Replicate 3 (depth=60mm)
Foose et al. (2002) (depth=60mm)
POLLUTE (depth=60mm)
Replicate 2 (depth=90mm)
Foose et al. (2002) (depth=90mm)
POLLUTE (depth=90mm)
30
20
10
0
0
50
100
150
200
250
300
350
400
Time (days)
Forward “Class A” predictions using independently measured input
parameters (not calibrated)
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Summary Remarks
• Independent basic to applied research focused
on developing confidence in containment
facilities.
• Focus on topics that our stakeholders indicate
are important.
• Assess full-scale facilities and near full-scale
demonstrations, understand fundamental
mechanisms, and create/validate predictive
models.
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