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Contrasts in LNAPL Risk Factors for Different Petroleum Products Presented by: G.D. Beckett, PG, CHG; AQUI-VER, INC. Douglas Bell, PG; Dillon Consulting

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Two Key Components - Both Important Physics of Release

Chemistry of Release

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Simulated Transient LNAPL Release, 2 Darcy Sand Time 0 S

N

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Simulated Transient LNAPL Release, Time 1 Early-Time S

N

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Simulated Transient LNAPL Release, Time 2 Mid-Time S

N

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Simulated Transient LNAPL Release, Time 3 Late-Time S

N

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The Range of Impacts Depend on the LNAPL 1. Distribution of spill Release Source

2. Chemical character of spill 3. Transport characteristics

Residual LNAPL Water Table

“Stuck” NAPL q

Water Table

Dissolved Phase q

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Oil Products Vary Physically

Heavy Fuel & Crude Oils

Light Oils

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Each Have Differing Chemistry

Jet A

Gasoline

Diesel

Motor Oil

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Relative Mobility of Different Products to Water 100

Parameter Value

10

1

Viscosity (cP)

0.1

Density (g/cc) Mobility Factor il O de C ru

Fu el O il #4

Fu el O il #2

l# 2 D ie se

-5 JP & 4 JP -

N ap th a

G

as ol in e

0.01

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Effective NAPL Conductivity (cm/sec)

Effective NAPL Conductivity

Gasoline Diesel Oil

10 -2 10 -3 10 -4

K ' kr ki

Df g

µf

10 -5 10 -6 10 -7 10 -8 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NAPL Saturation © AQUI-VER, INC.

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What the Heck Does All that Mean? • Each product will behave differently – Physically & chemically

• Each has a different relevance – Different fate & transport – Different receptor implications – Different cleanup implications

• But, NAPL is often treated uniformly – From a reaction point of view • Remove it from the ground

– And expectations tend to be uniform

• All that is out of step with realities – Physical & chemical

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Comparative Lateral LNAPL Migration Gasoline

Large Medium Small

Diesel

Large Medium

Diesel Heavy Oil

Silty Sand

Gasoline

Heavy Oil

Sand

(converse is true for vertical migration)

Small Large Medium Small Large Medium Small Large Medium Small Large Medium Small

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

Meters from Release

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Relative Mobility & Mass Comparison Silty Sand

Clean Sand

1.E+00 Relative Mass Relative K

Relative Mass or Conductivity

1.E-01

1.E-02

1.E-03

1.E-04

1.E-05

1.E-06 Gasoline Gasoline Gasoline 0.5m 1m 2m

Diesel 0.5m

Diesel 1m Diesel 2m Gasoline Gasoline Gasoline 0.5m 1m 2m

Diesel 0.5m

Diesel 1m Diesel 2m

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Chemistry Contrasts & Flux Magnitude

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(for same LNAPL & geologic conditions)

Chemical Compound: MTBE @ 2% Benzene @ 2% Xylenes @ 7.5% Fluorenes @ 2%

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Mass Loss Comparisons (cumulative water/vapor mass loss into environment) 1.E+04

1.E+03

Silty Sand - Gasoline Benzene Lost Silty Sand - Gasoline Toluene Lost Clean Sand - Gasoline Benzene Lost Clean Sand - Gasoline Toluene Lost

Silty Sand - Diesel Benzene Lost Silty Sand - Diesel Toluene Lost Clean Sand - Diesel Benzene Lost Clean Sand - Diesel Toluene Lost

Mass Loss (kg)

1.E+02

1.E+01

1.E+00

1.E-01

1.E-02 1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04 © AQUI-VER, INC.

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How Does All that Stack Up? • Heavier oils are far less risk – Though light oils may also pose no risk

• Gasoline is much more mobile – ~10x more than diesel – ~ 100s - 1000s times more than heavier oils

• Fuel oils present much lower mass fluxes – Less loading to the environment – 100s to many 1000s times less risk

• In total, these contrasts are on different playing fields – Why is our management on the same one?

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LNAPL Management Considerations • Tend to focus on LNAPL mobility evaluations – – – –

Weight of evidence Residual saturations Site specific mobility calculations Inherent mobility (bail-down & tech evaluations)

• LNAPL plumes stabilize with time as saturations decrease • Residual LNAPL as secondary source – Dissolved Phase / Vapor Phase

• Incorporate risk-based principles – risk magnitude / risk longevity – Risk reduction

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Business Considerations • LNAPL liability issues (ex. SOX) – Financial statements – Third party disclosure

• Establish LNAPL liability management policy – How to define? – Environmental approach (tier 1, 2, 3) – Accounting approach

• Demonstrate LNAPL liabilities are under control – How to measure ?

• Manage ongoing LNAPL assessment/remediation – Portfolio approach – Reduction in overall liability – Fiscally sustainable and responsible © AQUI-VER, INC.

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Enhanced LNAPL Management Strategy • Characterize site(s) to delineate extend of LNAPL (and associated) impacts – including LNAPL chemistry

• Confirm stability of LNAPL plumes and associated impacts – Technically defensible – Identify trans-boundary and receptor/pathway concerns

• Evaluate and rank LNAPL site(s) on a risk basis – Strategic portfolio management – Be aware of other drivers (real estate)

• Manage Expenditures – Focus on high risk/high liability sites – Cash flow and annual budget considerations – External and internal economic factors © AQUI-VER, INC.

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LNAPL Summary • Physical properties of product are directly related to hydrocarbon mobility and related risk factors – True for all ‘phases’ of impact – Ex. Gasoline greater concern than Diesel

• Strategic management of LNAPL sites incorporating riskbased approaches direct remedial/management effort to greatest risk/liability reduction – Maximize effective $$

• Critical to distinguish between product types when evaluating and managing LNAPL sites. © AQUI-VER, INC.