a role for natural analogs in the design and long-term
TRANSCRIPT
A Role for Natural Analogs in the Design and Long-Term Performance
Evaluation of Earthen Covers for Uranium Mill Tailings?
WJ WaughS.M. Stoller Corporation
NRC Workshop on Engineered Barrier PerformanceAugust 3-5, 2010
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Remedies at most LM sites are covered disposal cells for U mill tailings.
Broad range of climates, soils, and ecology.
U.S. Department of Energy Office of Legacy Management (LM) Sites
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Tailings
Low-Permeability Radon Barrier
15 cm
30 cm
60 cm
Bedding
Rock Riprap
Conventional Cover Design
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Alternative Cover Design
Gravel Admixturein Upper 20 cm
Vegetation (ET)
Geotextile Separator
Topsoil61.0 cm
Animal Intrusion Layer(Cobbles Filled w/ Soil)30.5 cm
Capillary Barrier(Coarse Sand)
38.0 cm
Growth Medium and Frost Protection(Fine-Grained Soil)
41.0 cm
Fine-Grained Soil30.5 cm
Wat
er S
tora
ge L
ayer
(Spo
nge)
163
cm
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Ecology Happens – Deal With It!
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Ecology Happens – Deal With It!Ecosystem Engineering Paradigm♦ Earthen covers are engineered ecosystems—
manipulations of soils and ecology.
♦ Initial state of cover is quite dissimilar to but greatly influenced by the surrounding ecosystem.
♦ Climatic variability, soil development, and ecological succession can fairly rapidly alter engineered soil properties and cover performance.
♦ Analogs provide evidence for understanding changes in climate, soils, and ecology, and for increasing confidence in cover sustainability.
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Long-Term PerformanceEvaluation Tools
Monitoring
Natural AnalogsNumerical
Models
LongLong--TermTermPerformPerform--
anceance
Monitoring
Natural AnalogsNumerical
Models
LongLong--TermTermPerformPerform--
anceance
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Monitoring
NumericalModels
Natural Analogs
LongLong--TermTermPerformPerform--
anceance
Monitoring
NumericalModels
Natural Analogs
LongLong--TermTermPerformPerform--
anceance
Monitoring
NumericalModels
Natural Analogs
LongLong--TermTermPerformPerform--
anceance
1. Understanding long-term degradation processes,
2. Designing more sustainable covers
3. Defining scenarios for modeling long-term performance, and
4. Monitoring precursors of change
Natural Analogs Can IncreaseConfidence in Long-Term Performance
by Providing Evidence for…
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Monitoring
Natural AnalogsNumerical
Models
LongLong--TermTermPerformPerform--
anceance
Monitoring
Natural AnalogsNumerical
Models
LongLong--TermTermPerformPerform--
anceance
Performance Evaluation Tools
Long-Term Risk-BasedPerformance EvaluationProcess(Ho et al. 2004)
((Cliff Ho, SNLCliff Ho, SNL))
Scenario 2Scenario 1
Select Select Reject
Scenario 3
Develop and Screen Scenarios
ClimateEvapotranspirationSource TermVadose ZoneSaturated ZoneHuman Exposure
Develop Models
Perform Calculations00E000E000E000E000E000E000E000E000E000E000E000E0000D63768118>I<FFF8FFF8FFF80038003800380038003800380038003800380038003800380038003800380038003003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380038003800380
Risk/PerformanceCost/ScheduleRegulatory C ompliance
Interpret Results
KsatClimate Change Defects
Estimate Parameter Ranges and Uncertainty
Leaf Area
PA_process.aiCliff Ho, SNL
Natural Analog Examples
Lakeview, OR Burrell, PA
Monticello, UTDurango, CO
Grand Junction, CO
Hanford, WA
Natural Analog Examples
Monticello, UT
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Storage Storage Change (Change (ΔΔS)S)
Long-Term Degradation Processesand Natural Analogs
Climate Change
Ecological Change
Soil Development
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Climate Change
IssueLong-term climaticshifts and variability
ToolsAnalogs of Past Climate
Proxy Paleoclimate Records:- Tree rings- Packrat middens- Lake pollen- Ice cores- Archaeology
Climate Change ModelsClimate Analog Sites
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Uranium Mill Tailings Disposal Sites and PaleoclimateReconstruction Sites in theFour CornersRegion
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Examples ofProxy PaleoclimateData Sites
– Fishmouth CavePackrat Middens
– Duck LakePollen in Sediments
Molas Lake –Pollen in Sediments
La Plata Mtn –Timberline Tree Rings
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Generalized Forest Boundary Shifts
34 cm, 8 oC
80 cm, 2 oC 80 cm, 6 oC
60 cm, 10 oC 39 cm, 7.8 oC
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Monticello Climate Analog Sites
Warm/WetMesa Verde NP
Monticello, UT(390 mm 7.8 oC)
Cold/WetFt Lewis, CO(470 mm 6.1 oC)
Warm/DryBlanding, UT(340 mm 10.1 oC)
Cold/DryNorthdale, CO
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250 300 350 400 450 500 550
Precipitation (mm)
Tem
pera
ture
(oC
)• Used paleoclimate data and climate change models to
develop scenarios for future climate of Monticello • Located present-day soil/vegetation analogs of future
climate scenarios
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Monticello Climate Analog Sites
Monticello
Fort Lewis(Cold/Wet)
Utah Colorado
New MexicoArizona
Blanding(Warm/Dry)
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Soil Development
AnalogsHydraulic and edaphicproperties of natural and archaeological soils
IssueEffects of soil develop-ment on hydraulic and edaphic properties– Soil structure– Illuviation/eluviation– Bioturbation– Soil erosion/deposition
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Fort Lewis, CO: Soil Morphology and Hydrology
Fort Lewis Pit- Cool/wet analog- Early Holocene- Fine sandy loam- Blocky structure- Ksat = 4 x 10-7 m/s
(Tension Infiltrometer)
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Archaeological Analog: Soil Morphology and Hydrology
Date: 1270 ± 40 BP
Soil Morphology:– Blocky/prismatic
structure– Bioturbation– Calcareous horizon
Ksat: ~ 10-6 m/s
Blanding, Utah Warm/dry Climate AnalogAnasazi Kiva Excavation
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Ecological Change
AnalogsStructural and functionalecology of successionalchronosequences
IssueEffects of climate change, soil development, and disturbances (e.g., fire, drought, grazing) on plant, animal, and soil ecology
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Ecological Response to Climate: Vegetation / LAI Chronosequence
Ft. Lewis, CO- Ponderosa pine /
scrub oak- LAI = 1.46
Ft. Lewis, COFt. Lewis, CO-- Ponderosa pine / Ponderosa pine /
scrub oakscrub oak-- LAI = 1.46LAI = 1.46
Monticello, UT- Sagebrush /
western wheatgrass- LAI = 1.36
Monticello, UTMonticello, UT-- Sagebrush / Sagebrush /
western wheatgrasswestern wheatgrass-- LAI = 1.36LAI = 1.36
Blanding, UT- Sagebrush /
blue grama- LAI = 0.53
Blanding, UTBlanding, UT-- Sagebrush / Sagebrush /
blue blue gramagrama-- LAI = 0.53LAI = 0.53
Climate Gradient:warm/dry to cool/wetSoils: Deep, eolian, fine sandy loam
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Goal:Mimic ecology and high ET of diverse native and naturalized vegetation
Sagebrush steppe
Old-field succession
Baseline Ecology:Characterize vegetation and soils at reference sites (analogs) to develop revegetation targets and acceptance criteria
Cover Revegetation Analogs
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Cover Revegetation
1999
Transplanted and Irrigated:Sagebrush
Drill Seeded:Grasses, forbs,and other shrubs
2000
cheatgrassyellow sweetclover
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Monticello Cover Vegetation – 2008
2008
Natural Analog Examples
Burrell, PA
Burrell Cover Ksat Results
(n=3)
No Plants2.9 x 10-9 m/s (a)
Trees(sycamore, sumac, black locust)2.2 x 10-9 m/s (a)
Japanese knotweed3.8 x 10-7 m/s (b)
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Ksat = 1.3 x 10–6 m/s(n=3)
Hannastown, PAKsat and LAI at an analog site with the same soil series as the Burrell CSL
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Burrell Leaf Area Index (LAI)
LAI*Burrell Cover 0.65(knotweed) ± 0.07
(n=100)
Hannastown 5.12Analog ± 0.12(sugar maple) (n=200)
Natural Analog Examples
Lakeview, OR
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Air-entry permeametermeasurements of Ksat at soil borrow source
Ksat 1.6 x 10-7 m/s8.2 x 10-7 m/s2.9 x 10-6 m/s
Permeability of cover CSL and native soil are about the same
Lakeview CSL Borrow Soil
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Lakeview Climate Change:Wet and Dry Ecology Analogs
Conifer Site, ORSoil: Drews loamVegetation: Mixed coniferLAI: 1.62
Guano Basin Site, NVSoil: Spangenburg loamVegetation: Big sagebrushLAI: 0.43
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Grass Reference LAI = 0.55
Grass Grass Reference Reference LAI = 0.55LAI = 0.55
2003 Top Slope LAI = 0.28
2003 2003 Top Slope Top Slope LAI = 0.28LAI = 0.28
Lakeview Ecology Analog: LAI Fire Chronosequence
Sagebrush LAI = 0.77Sagebrush LAI = 0.77Sagebrush LAI = 0.77
Bitterbrush LAI = 1.28Bitterbrush LAI = 1.28Bitterbrush LAI = 1.28
Natural Analog Examples
Grand Junction, CO
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Grand Junction Disposal Cell andNatural Analog of Design Renovation
Glacial debris flow nearby
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Rock / ET Cover Natural Analog:Beaver Gulch, Colorado
Glacial debris flownear GJ U-tailingsdisposal cell
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Natural Analog of Cover Renovation:Evidence of Slope Age, Stability, and Water Balance
Rock varnish, lichen growth on basalt stones, slope geometry
Late Pleistocene>10,000 years
Soil Morphology: argillic and calcichorizons
Adequate plantcover and low soil water movement below the roots
Natural Analog Examples
Durango, CO
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Durango, CO Side Slope Plant Ecology
• Multi-layered top slope design• Rock side slope design
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Durango, COSide Slope Analog
Analog:Duckett Ridge
slide rock
Durango coverrock side slope
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Durango, COSide SlopeAnalog
PlantSuccessional
ChronosequenceOrganic soil developmentOrganic soil development
Gambel oak seral stageGambel oak seral stage
Quaking aspen seral stageQuaking aspen seral stage
Natural Analog Examples
Hanford, WA
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Hanford, WA Capillary Barrier Analog
Pedogenic carbonates:Indicator of 10,000-yearsoil water balance
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Hanford, WA Coppice Dune Ecology Analog
Warden silt loam -Borrow sourcefor ET cover soil
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Hanford, WA Coppice Dune Ecology Analog
Water storagechanges (neutron hydroprobe) indune and swalesoil profiles
(Ambient Ppt)
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Hanford, WASecondary Plant Succession Analog
Pristine site dominated by wheatgrassfollowing a burn
Old-field sitedominated by
cheatgrassfollowing a burn
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Hanford, WASecondary Plant Succession Analog
Soil Water Storage
Cheatgrass vs. Wheatgrass (Ppt = 180 mm, 7.1 in)
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SummaryAnalogs may provide evidence for
Understanding long-term degradation processes including climate change, soil development, and ecological change
Sustainable cover designs and renovation
Developing scenarios for into to models of long-term performance
Monitoring precursors (indicators) of long-term degradation processes