Field Verification of Computer CodesField Verification of Computer Codes for Predicting the Fate and Transport of for Predicting the Fate and Transport of

Salt in Soil and GroundwaterSalt in Soil and Groundwater

Malcolm Reeves, Erin McCaig, Andrew Karvonen

MDH Engineered Solutions Corp.

Tony Knafla

Equilibrium Environmental Inc.

2

R & D ProvidersR & D Providers

Alberta Environment

City of Calgary

Petroleum Technology Alliance of Canada

3

Significance to IndustrySignificance to Industry

• Why model the fate and transport of salt?Why model the fate and transport of salt?– to integrate data from diverse sourcesto integrate data from diverse sources– to highlight data deficienciesto highlight data deficiencies– to test conceptual hypothesesto test conceptual hypotheses– to quantify “unknowns”to quantify “unknowns”– to establish probable historyto establish probable history– to predict the future from the pastto predict the future from the past– to assess alternative remedial measuresto assess alternative remedial measures

4

Project OverviewProject Overview

• The project was conducted by MDH Engineered The project was conducted by MDH Engineered Solutions Corp and involved two successive Solutions Corp and involved two successive phases between October 2003 and March 2004phases between October 2003 and March 2004

• Field StudiesField Studies – Collected and supplemented data from four Collected and supplemented data from four

diverse field sitesdiverse field sites• Numerical Model StudiesNumerical Model Studies

– Verified ability recommended computer Verified ability recommended computer codes to predict the behaviour of salt at four codes to predict the behaviour of salt at four diverse field sitesdiverse field sites

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SourcesSources

• Model contaminant sources M(x,t) = Q(x,t).C(x,t) can be Model contaminant sources M(x,t) = Q(x,t).C(x,t) can be entered into models in different ways, for example:entered into models in different ways, for example:

• Boundary ConditionsBoundary Conditions– Specified mass flux on a boundarySpecified mass flux on a boundary

– Specified concentration on a boundary Specified concentration on a boundary

• Initial ConditionsInitial Conditions– Specified spatial distribution of total mass at some time Specified spatial distribution of total mass at some time

– Specified spatial distribution of concentration at some timeSpecified spatial distribution of concentration at some time

• Observed data can be used to :Observed data can be used to :– specify an initial condition for forward modelling specify an initial condition for forward modelling

– predict an initial condition by history matchingpredict an initial condition by history matching

– Help determine (calibrate) material propertiesHelp determine (calibrate) material properties

– ..............................

• Ideally, model verification requires sites where material properties Ideally, model verification requires sites where material properties and sources are fully known in time and space.and sources are fully known in time and space.

6

Instantaneous SourcesInstantaneous Sources

Diffusion Advection & Diffusion/Dispersion

tot1t2 to

t1

t2

7

Ambiguous SourcesAmbiguous Sources

Same Source Mass

Same Source Distribution

Different Material Properties

Different Diffusion Time

tot1 tot2

= Same Concentration Profile

8

Ambiguous SourcesAmbiguous Sources

Same Material Properties

Same Source Mass

Different Source Distribution

Different Diffusion Time

tot1 tot2

= Same Concentration Profile

9

Ambiguity ExplainedAmbiguity Explained

= = √√ (D/2t) (D/2t)

There is an infinity of choices for D and t for the There is an infinity of choices for D and t for the same distribution parameter same distribution parameter

AA = = √√ (D/2t (D/2tAA)) = = √√ (D/2t) (D/2t)

Initial source distribution at time tInitial source distribution at time tAA with the with the distribution parameter distribution parameter AA will give distribution will give distribution parameter parameter after time (t –t after time (t –tAA), identical to a ), identical to a uniform source after time t.uniform source after time t.

10

Field SitesField Sites

• Site A Heavy oil sludge soil augmentation trialSite A Heavy oil sludge soil augmentation trial– Sandy soil Sandy soil – Deep naturally-attenuated saturated zone plumeDeep naturally-attenuated saturated zone plume

• Site B Drilling mud disposal trial Site B Drilling mud disposal trial – Clay soil Clay soil – Small shallow unsaturated zone plumeSmall shallow unsaturated zone plume

• Site C Pipeline break Site C Pipeline break – Clay soil Clay soil – Small shallow unsaturated zone plume Small shallow unsaturated zone plume

• Site D Road salt storage Site D Road salt storage – Silty sand and sandstone bedrockSilty sand and sandstone bedrock– Shallow unsaturated and deep saturated zone plumesShallow unsaturated and deep saturated zone plumes

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Numerical CodesNumerical Codes• The ability of three public-domain codes to model the four sites was The ability of three public-domain codes to model the four sites was

verifiedverified

– CHEMFLO CHEMFLO • Oklahoma Agricultural Experiment Station (OAES)Oklahoma Agricultural Experiment Station (OAES)• 1D FDM unsaturated/saturated flow and transport1D FDM unsaturated/saturated flow and transport• Sorption reactionsSorption reactions

– UNSATCHEM UNSATCHEM • United States Salinity Laboratory (USSL)United States Salinity Laboratory (USSL)• 1D FEM unsaturated/saturated flow and transport1D FEM unsaturated/saturated flow and transport• Ion exchange, sorption reactionsIon exchange, sorption reactions

– VS2DTI VS2DTI • United Sates Geological Survey (USGS)United Sates Geological Survey (USGS)• 2D FDM unsaturated/saturated flow and transport2D FDM unsaturated/saturated flow and transport• Ion exchange, sorption reactionsIon exchange, sorption reactions

• Also included for continuity with earlier workAlso included for continuity with earlier work– LEACHMLEACHM

• J.Huston (researcher)J.Huston (researcher)• 1D FDM unsaturated flow and transport1D FDM unsaturated flow and transport• Ion exchange, sorption reactionsIon exchange, sorption reactions

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Site C: Pipeline Break Site PlanSite C: Pipeline Break Site Plan

BH 5, MW 03-5

BH 02-1

MW 02-3A

BH 4, MW 03-4

BH 7, MW 03-7A

BH 02-1A

BH 02-1B

BH 8, MW 03-8CBH 8, MW 03-8B

BH 8, MW 03-8A

BH 02-2 BH 6, MW 03-6

MW 02-2A (destroyed)

Excavation Boundary to 2.0 mbgs

Estimated Impact Area

0 m 100 mScale 1:1000

PipelineN

BH 1

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Site C: Pipeline Break ProblemSite C: Pipeline Break Problem

SandKs= 1x10-5 m/s

0 mbgs

10 mbgs

2.5 mbgs

3.5 mbgs

Water Table at 3.6 mbgs

Infiltration = 2 mm/yr

Constant Pressure Head = 6.4 m

Ks= 8x10-8 m/s

Instantaneous Applied Source = 70 g/L Chloride

(1715 kg)

Silty Clay

Ks= 3x10-8 m/sClay Till

Models Used:

•UNSATCHEM

•CHEMFLO

• LEACHM

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Site C: Pipeline Break ResultsSite C: Pipeline Break Results

Sand

0 mbgs

10 mbgs

2.5 mbgs

3.5 mbgs

Silty Clay

Clay Till

0 18 5 10 15

Chloride Concentration (g/L)

70 g/L Chloride

BH-02-02BH1

UNSATCHEM Result

LEACHM Result

17.211.8

17.0

17.1

Time = 2002

CHEMFLO Result

17.0

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Site C: Pipeline Break ResultsSite C: Pipeline Break Results

Sand

0 mbgs

10 mbgs

2.5 mbgs

3.5 mbgs

Silty Clay

Clay Till

0 10.0 2.5 5.0 7.5

Chloride Concentration (g/L)

70 g/L Chloride

CHEMFLO Result

BH8UNSATCHEM Result

3.33.3

4.4

Time = 2003

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Site C: Pipeline Break DiscussionSite C: Pipeline Break Discussion

• Site C is a shallow site in a clay soilSite C is a shallow site in a clay soil• The source release is recent (4 years)The source release is recent (4 years)• Little movement has occurredLittle movement has occurred• Model match is precise and easy to obtainModel match is precise and easy to obtain• BUT……BUT……• Source term is unconstrainedSource term is unconstrained• Solution is highly ambiguousSolution is highly ambiguous• Any predictions likely of low reliabilityAny predictions likely of low reliability

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Site B: Drilling Mud Site PlanSite B: Drilling Mud Site Plan

Type of Chloride Application Application

Rate (kg/ha)

KCl 1 0

2 5003 10004 20005 4000

NaCl

6 07 3508 7009 1400

10 2800  

Boreholes used to verify model

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Site B: Drilling Mud ProblemSite B: Drilling Mud Problem

0 mbgs

20 mbgs

Water Table at 16 mbgs

Infiltration = 20 mm/yr

Constant Pressure Head = 4.0 m

Applied Source = 9.7 g/L Chloride

3400 kg/ha

Ks= 4x10-9 m/sSilty Till

Models Used:

•UNSATCHEM

•CHEMFLO

•LEACHM

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Site B: Drilling Mud ResultsSite B: Drilling Mud Results

0 mbgs

20 mbgs

9.7 g/L Chloride

Ks= 4x10-9 m/sSilty Till

0 400100 200 300

Chloride Concentration (mg/L)

370

27085

160

10 mbgs

5 mbgs

15 mbgs

290 280

M413-JM413-K

M413-L

M413-DUNSATCHEM Result

LEACHM Result

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Site B: Drilling Mud DiscussionSite B: Drilling Mud Discussion

• Site B is a shallow site in a clay soilSite B is a shallow site in a clay soil• The source release is relatively old (16 years)The source release is relatively old (16 years)• Relatively little movement has occurredRelatively little movement has occurred• Present day data is scatteredPresent day data is scattered• Model match is not exact and difficult to obtainModel match is not exact and difficult to obtain• BUT……..BUT……..• Source term is reasonably well constrainedSource term is reasonably well constrained• Lateral dilution affects 1D models in long termLateral dilution affects 1D models in long term• History match should “over predict” peak concentration History match should “over predict” peak concentration • 1D model is inherently conservative over time1D model is inherently conservative over time• Predictions likely upper bound estimatesPredictions likely upper bound estimates

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Site A: Heavy Oil Sludge Site PlanSite A: Heavy Oil Sludge Site Plan

To

Hw

y #16

Bush

Bush

Bush

0 m 100 m

Scale 1:3000

M413-19

M413-24

M413-16

M413-22

M413-7

M413-2

M413-5

M413-20

M413-15

M413-1

Topographic Low

FC CC

CC

N

FC Fallow Crop

CC Continuous Crop

Original Boreholes

2004 Boreholes

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Site A: Heavy Oil Sludge ProblemSite A: Heavy Oil Sludge Problem

0 mbgs

14 mbgs

Water Table at 3.2 mbgs

Infiltration = 2 mm/y

No Flow Boundary

Applied Source = 220 g/L Chloride

for 3 months

Silt Ks= 1x10-6 m/s

Model Used:

•VS2DTI

Ks= 2x10-8 m/s

Till

Ks= 8x10-4 m/s

Sand

Infiltration = 12 mm/yInfiltration = 12 mm/y

10 mbgs

Direction of Groundwater Flow

0 m 680 m

No

Flo

w B

ou

nd

ary

Total Head = - 3.2 m

Seepage Face5 mbgs

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Site A: Heavy Oil Sludge ModelSite A: Heavy Oil Sludge Model

Moisture Content

Saturation

Pressure Head

Darcy Flux

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Site A: Heavy Oil Sludge ResultsSite A: Heavy Oil Sludge Results

1 year

10 years

5 years

15 years

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Site A: Heavy Oil Sludge ResultsSite A: Heavy Oil Sludge Results

18 years

Applied Source = 220 g/L Chloride

for 3 months

Seepage Face

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Site A: Heavy Oil Sludge DiscussionSite A: Heavy Oil Sludge Discussion

• Site A is a relatively deep site in a sandy soilSite A is a relatively deep site in a sandy soil• The source release is relatively old (18 years)The source release is relatively old (18 years)• Much movement has occurredMuch movement has occurred• Present day data is ambiguousPresent day data is ambiguous• 2D saturated/unsaturated model needed2D saturated/unsaturated model needed• Model match is not exact and difficult to obtainModel match is not exact and difficult to obtain• BUT……..BUT……..• Source term is reasonably well constrainedSource term is reasonably well constrained• Model simulation is plausibleModel simulation is plausible• Results are consistent with site dataResults are consistent with site data

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Site D: Road Salt Storage Site PlanSite D: Road Salt Storage Site Plan

Infiltration Gallery

Bow River

21

Retention Pond

Ma

in B

uil

din

g

Bearspaw Dam Road

Canadian Pacific Rail Line

Salt Storage

Area

Bushes

11

7 S

t N

W

Parking Area

Bus Parking & Storage

Area

Stockpile Aggregate with NaCl

Silo with Pure NaCl

Stockpile Aggregate with NaCl & CaCl

3

1

2

3

N

0 m 100 m

Scale 1:2000

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Site D: Road Salt Storage ProblemSite D: Road Salt Storage Problem

0 mbgs

22 mbgs

Water Table at 6.5 mbgs

No Flow Boundary

Applied Source = 220 g/L Chloride

Annually for 2 months

Silty Sand

Model Used:

•VS2DTI

Ks= 2.5x10-6 m/s

Sandstone

Infiltration = 20 mm/yr

8.5 mbgs

Ks= 5.0 x10-6 m/s

13.5 mbgs

Pressure Head = 0 m

Pressure Head = 0 m

0 m 334 m

Total Head = - 6.5 m

No Flow Boundary

Ks= 1.25 x10-9m/s

Shale

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Darcy Flux

Site D: Road Salt Storage ResultsSite D: Road Salt Storage Results

Moisture Content

Saturation

Pressure Head

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Site D: Road Salt Storage ResultsSite D: Road Salt Storage Results

1 year 5 years

19 years 46 years

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Site D: Road Salt Storage DiscussionSite D: Road Salt Storage Discussion

• Site D is a relatively deep site in a sandy soilSite D is a relatively deep site in a sandy soil• The source release is relatively old (25+ years)The source release is relatively old (25+ years)• Much movement has occurredMuch movement has occurred• Present day data is clear at discharge pointPresent day data is clear at discharge point• 2D saturated/unsaturated model needed2D saturated/unsaturated model needed• Model match is not exact and difficult to obtainModel match is not exact and difficult to obtain• BUT……..BUT……..• Source term is reasonably well constrainedSource term is reasonably well constrained• Model simulation is plausibleModel simulation is plausible• Results are consistent with site dataResults are consistent with site data

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ConclusionsConclusions

• Model results mimic observed data using information from Model results mimic observed data using information from detailed site investigationsdetailed site investigations

• CHEMFLO, UNSATCHEM, VS2DTI performed as expected and CHEMFLO, UNSATCHEM, VS2DTI performed as expected and were verified at three siteswere verified at three sites

• The pipeline-break site could not be used for verification but the The pipeline-break site could not be used for verification but the modelling helped constrain the probable mass spilledmodelling helped constrain the probable mass spilled

• Recent shallow spills are easy to match with models but Recent shallow spills are easy to match with models but predictive capability is likely limitedpredictive capability is likely limited

• The verification study suggested that reduced data sets would The verification study suggested that reduced data sets would make model conceptualization much less reliable make model conceptualization much less reliable

• Modelling provided a powerful interpretive and predictive tool Modelling provided a powerful interpretive and predictive tool but is not a substitute for high-quality, site-specific databut is not a substitute for high-quality, site-specific data

33

AcknowledgementsAcknowledgements

Alberta Environment

PTAC Soil Salinity Working Group

Special thanks to:

Les Henry, Professor Emeritus, Soil Science, U of S

Dan Bulat, Envirotech Engineering Inc.

Roxanne Pauls, MDH Engineered Solutions Corp

March, 2005March, 2005

Thank you for your attentionThank you for your attention