A Role for Natural Analogs in the Design and Long-Term

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


Models


anceance

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Monitoring

NumericalModels

Natural Analogs


anceance

Monitoring

NumericalModels

Natural Analogs


anceance

Monitoring

NumericalModels

Natural Analogs


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


Models


anceance

Monitoring


Models


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


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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6

7

8

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10

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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


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)


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


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


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


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

Documents

A Role for Natural Analogs in the Design and Long-Term