LNAPL Transmissivity End Points Why, How and When...LNAPL Transmissivity End Points Why, How and When Andrew Kirkman P.E. 1. LNAPL Transmissivity (Tn) ... − Or 80% recovery of a

LNAPL Transmissivity End Points Why, How and When

Andrew Kirkman P.E.

1

LNAPL Transmissivity (Tn)

• LNAPL Transmissivity summarizes the following key considerations in LNAPL recovery into one metric:

− LNAPL Density

− LNAPL Viscosity

Tn = ∑Kn ∆∆∆∆bn

Well

LNAPL

9/16/2013LNAPL Transmissivity Endpoints

− Soil permeability

− Magnitude of LNAPL saturation in soil (i.e., LNAPL concentration)

− Thickness that LNAPL flows over

n

rnnn

kkgK

µρ ⋅⋅⋅=

Water

2

A Pipe =

Max Zero

Permeability

Permeability K1>0K2<K1

How Transmissivity Relates to Reduction of Mobile LNAPL


Max PermeabilityPermeability

As LNAPL is recovered the number of pores occupied by LNAPL decreases, which in turn decreases its relativepermeability. This is reflected in a decrease in LNAPL Transmissivity

3

30.0

35.0

RE

CO

VE

RE

D L

NA

PL

TH

ICK

NE

SS

(F

T)

MW-1 2008 MW-4 2004 UNCONFINED MW-18 2007 MW-4 2008 CONFINED MW-6 2008

Gauged Thickness –Poor Metric for Recoverability

• MW-4 Confined recovers to 5 feet thickness fast than wells with 33 feet of starting thickness

• MW-18 expected to take 3 years to recover to ~35 ft of thickness


0.0

5.0

10.0

15.0

20.0

25.0

1 10 100 1000 10000 100000 1000000

RE

CO

VE

RE

D L

NA

PL

TH

ICK

NE

SS

(F

T)

ELAPSED TIME (MIN) ~ 2 weeks4

33.1533.00100

LN

AP

L R

EC

OV

ER

Y M

ET

RIC

VA

LU

E

WATER ENHANCED RECOVERY AT 1 FOOT OF DRAWDOWN (GPD)

LNAPL SKIMMING RATE (GPD)

GAUGED LNAPL THICKNESS (FT)

Gauged LNAPL Thickness Versus Recovery - Poor Correlation


19.03

2.605.40

0.01

0.1

1

10

MW-1MW-4 UNCONFINED

MW-4 CONFINEDMW-6MW-18

LN

AP

L R

EC

OV

ER

Y M

ET

RIC

VA

LU

E

5

LNAPL Transmissivity Versus RecoveryGood Correlation

• LNAPL Transmissivity exhibits improved correlation

• LNAPL Recovery Rate is a Function of both drawdown induced and LNAPL transmissivity

• Skimming drawdown is controlled by equilibrium fluid levels and soil profile

LN

AP

L R

EC

OV

ER

Y M

ET

RIC

VA

LU

E

WATER ENHANCED RECOVERY AT 1 FOOT OF DRAWDOWN (GPD)

LNAPL SKIMMING RATE (GPD)

LNAPL TRANSMISIVITY (FT2/DAY)


5.2

3135

0.22

0.0070.001

0.01

0.1

1

10

100

MW-1MW-4 UNCONFINEDMW-4 CONFINEDMW-6MW-18

LN

AP

L R

EC

OV

ER

Y M

ET

RIC

VA

LU

E

6

Why use LNAPL transmissivity?

•LNAPL Thickness

− Inconsistent between hydraulic scenarios (perched, confined, unconfined)

− Inconsistent between soil types

− Poor indicator of LNAPL recovery

•LNAPL Recovery Rate More Robust Metric than LNAPL Thickness

− Need recovery system or pilot test data


− Need recovery system or pilot test data

− Operational variability and technology differences make it difficult to use across technologies and/or sites

•Transmissivity

− Estimated with recovery data or field testing on monitoring wells

− Consistent across soil types

− Consistent across confined, unconfined or perched conditions

7

In well LNAPL thickness is a poor metric

• ITRC (2010) - recover LNAPL from areas with the largest equilibrium in well

thicknesses BUT

− Poor metric: correlates unfavorably with LNAPL recoverability

− Does not account for soil and LNAPL properties, soil heterogeneity, and LNAPL aquifer

conditions (unconfined/perched/confined)

• ASTM (2005) –


• ASTM (2005) –

− LNAPL regulatory policies that define remediation metrics by small LNAPL thickness in

wells are…often inconsistent with risk-based screening levels and with current technical

knowledge regarding LNAPL mobility and recoverability ¶ 5.14.

Short Term Recovery Evaluation

0.4

0.5

LNA

PL

Tra

nsm

issi

vity

(ft2

/day

)

40

50

LNA

PL

Rec

ove

ry R

ate

(gp

d)

Wat

er R

eco

very

Rat

e (1

000

gp

d)

LNAPL Transmissivity LNAPL Recovery Rate Water Recovery Rate


0

0.1

0.2

0.3

Dec-06 Jan-07 Feb-07 Mar-07 Apr-07

LNA

PL

Tra

nsm

issi

vity

(ft

0

10

20

30

LNA

PL

Rec

ove

ry R

ate

(gp

d)

Wat

er R

eco

very

Rat

e (1

000

gp

d)

w

orwo QQTT ρ=

Page

So What Transmissivity Value Means

there’s a Bunch of LNAPL There

• New Catastrophic release scenario’s have resulted in observed values of 80 ft2/day

− ~1% of other sites exhibit Tn values this high several /decades after the release period

• Consider the Theim Equation

− 80 ft2/day with 1 ft of drawdown results in 816

− Or 80% recovery of a 700k release in 2 years with 6 skimming wells


− Or 80% recovery of a 700k release in 2 years with 6 skimming wells

• LNAPL Tn of 0.1 ft2/day with 0.1 ft of drawdown results in <0.2 gpd

− How does this rate compare with the remaining LNAPL mass?, mobile mass?, residual mass?

− Does it matter if migration is documented

10

LNAPL TRANSMISSIVITY CURVES

3.7E+03

3.7E+04

3.7E+05

10

100

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PD

)LN

APL R

EC

OVERY R

ATE (G

PD

)LN

APL R

EC

OVERY R

ATE (G

PD

)LN

APL R

EC

OVERY R

ATE (G

PD

)

1 0.1 5 10 20 0.01

LNAPL Transmissivity in Practice

• Skimming LNAPL at 0.1 ft2/day

results in less than 400 GPY

skimming

• Skimming LNAPL at 5 ft2/day

results in 7300 GPY skimming


MULTI-PHASE & WATER

ENHANCED RECOVERY

VACUUM ENHANCED

SKIMMING RANGE

SKIMMING

RANGE

3.7E+00

3.7E+01

3.7E+02

3.7E+03

0.01

0.1

1

10

0.1 1 10

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PY)

LN

APL R

EC

OVERY R

ATE (G

PD

)LN

APL R

EC

OVERY R

ATE (G

PD

)LN

APL R

EC

OVERY R

ATE (G

PD

)LN

APL R

EC

OVERY R

ATE (G

PD

)

LNAPL DRAWDOWN (FT)LNAPL DRAWDOWN (FT)LNAPL DRAWDOWN (FT)LNAPL DRAWDOWN (FT)

Example Technology Drawdown Ranges

11

Ongoing support for LNAPL Transmissivity

• 2006 ASTM Guide of LNAPL Conceptual Site Models (E2531-06)

• 2009 ITRC Guide for LNAPL technology selection – includes LNAPL transmissivity range 0.1 to 0.8 ft2/day that corresponds to closed sites in various states

• 2011 ASTM Guide for Estimation of LNAPL Transmissivity

9/16/2013LNAPL Transmissivity Endpoints 12

• 2011 ASTM Guide for Estimation of LNAPL Transmissivity (E2856-13)

• API LNAPL Transmissivity work book

− search for LNAPL Baildown Test on API.org

− API multiple tools and documents – most pertinent here LNAPL baildown test spreadsheet and guide document

• Applied NAPL Science Review (www.napl-ansr.com)

− Online publication related to advancing LNAPL understanding within the remediation industry

ASTM LNAPL Transmissivity Standard (E2856-13)

• Increase Accuracy of calculations for LNAPL Transmissivity

• Identify critical assumptions and best practices

• Resolved various approaches into a more unified practice

• Include multiple methods in a single standard to provide comparison of methods


comparison of methods

• Provide standardization to generate a consistent and larger database of information

• Methods include:1. Baildown/Slug Tests (Lundy & Zimmerman

1999, Huntley, 2000 & Kirkman 2012)

2. Recovery System Data (Charbeneau, 2007)

3. Manual Skimming Tests

4. Tracer Tests (Sale, 2007)

13

LNAPL Concern – ITRC introduced composition vs saturation concern

BBB

Reduced LNAPL

saturation

Ben

zene

Con

cent

ratio

n in

Gro

undw

ater

(m

g/L)


CCC

Changed LNAPL

composition (less benzene)

Ben

zene

Con

cent

ratio

n in

Gro

undw

ater

(m

g/L)

15% 30%

LNAPL Saturation

Source: Dr. Sanjay Garg and ITRC LNAPL training

LNAPL Transmissivity and Endpoints for Hydraulic

Recovery

ITRC Endpoint Range 0.1 to 0.8 ft2/day

• Represents the LNAPL transmissivity that occurred at multiple sites that were closed with the following

support data/evidence

− LNAPL Recovery was asymptotic and small compared to residual LNAPL in place

− No risk to receptors via vapor or dissolved phase existed

− Remaining LNAPL was stable and not migrating

− Institutional controls were in place to prevent exposure


− Institutional controls were in place to prevent exposure

− Land/ groundwater use restrictions or;

− Active facilities ensured land use would remain industrial

− On going remediation would not significantly improve site conditions

− Plume already stable

− No complete pathways / risk to receptors

• Following Closure of LNAPL Transmissivity data was compiled and reviewed to generate the empirical Following Closure of LNAPL Transmissivity data was compiled and reviewed to generate the empirical Following Closure of LNAPL Transmissivity data was compiled and reviewed to generate the empirical Following Closure of LNAPL Transmissivity data was compiled and reviewed to generate the empirical

ITRC rangeITRC rangeITRC rangeITRC range

16

Stop Metric Example


What Fraction Can Be Removed for a

Given Starting LNAPL Transmissivity


9

11

13

15

170%

10%

20%

30%

40%

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

LN

APL T

RAN

SMIS

SIVIT

Y (FT

LN

APL T

RAN

SMIS

SIVIT

Y (FT

LN

APL T

RAN

SMIS

SIVIT

Y (FT

LN

APL T

RAN

SMIS

SIVIT

Y (FT

22 22 /D

AY)

/DAY)

/DAY)

/DAY)

REM

AIN

ING

VO

LU

ME (G

AL)

REM

AIN

ING

VO

LU

ME (G

AL)

REM

AIN

ING

VO

LU

ME (G

AL)

REM

AIN

ING

VO

LU

ME (G

AL)

ELAPSED ELAPSED ELAPSED ELAPSED TIME (YEARS)TIME (YEARS)TIME (YEARS)TIME (YEARS)

Reversed Decline

RESID

UAL

RESID

UAL

RESID

UAL

RESID

UAL

VO

LU

ME

VO

LU

ME

VO

LU

ME

VO

LU

ME

Remaining Volume Above Remaining Volume Above Remaining Volume Above Remaining Volume Above

ResidualResidualResidualResidual

LN

APL R

ecovered Above L

NAPL T

ransm

issivity of 0.6 ft


-3

-1

1

3

5

7

940%

50%

60%

70%

80%

90%

100%

LN

APL T

RAN

SMIS

SIVIT

Y (FT

LN

APL T

RAN

SMIS

SIVIT

Y (FT

LN

APL T

RAN

SMIS

SIVIT

Y (FT

LN

APL T

RAN

SMIS

SIVIT

Y (FT

REM

AIN

ING

VO

LU

ME (G

AL)

REM

AIN

ING

VO

LU

ME (G

AL)

REM

AIN

ING

VO

LU

ME (G

AL)

REM

AIN

ING

VO

LU

ME (G

AL)

Remaining Volume In Place LNAPL Transmissivity

19

LN

APL R

ecovered Above L

NAPL T

ransm

issivity of 0.6 ft 2/day

LN

APL

LN

APL

LN

APL

LN

APL

Recovered

Recovered

Recovered

Recovered

After

After

After

After

Reach

ing

Reach

ing

Reach

ing

Reach

ing

0.6 ft0.6 ft0.6 ft0.6 ft 22 22/day

/day/day/day

40%

50%

60%

70%

80%

90%

100%

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL W

ITH

IN M

OBIL

EW

ITH

IN M

OBIL

EW

ITH

IN M

OBIL

EW

ITH

IN M

OBIL

E

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

Fraction of LNAPL Within Proposed Endpoint Range

Fraction of LNAPL Beyond Proposed Recovery Endpoint/Continued to be Recovered with Significant Effort

Fraction of LNAPL Beyond Proposed Endpoint Range/was not Recovered

Residual LNAPL Fraction (unrecoverable)

8 years8 years

0.6 years

2 years

0.6 years

12 years

13.5 years

>10 years - Elapsed Time

Residual Fraction

Mobile FractionNot Recovered


0%

10%

20%

30%

40%

14 14 6 2 3.6 10 1.4 4.6 1.4 0.0015 - 0.0023 0.35

Well 7 Wells 8 - 21 Well 22 Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Wells 23 - 24 Well 25

Site 1 Site 2 Site 3 Site 4

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

6 years 14 years11 years

11 years

11 years

2 years

3.75 years

2 years

10 years10 years10 years10 years

>50 years>50 years>50 years>50 years

8 years7.5 years

4 years

Page 20

Time Until Transmissivity of 0.6 ft2/day (0.55 m2/day)

Recovery Time and FractionBeyond Endpoint

Not Recovered

Starting LNAPL Transmissivity (ft2/day)

Page 20

40%

50%

60%

70%

80%

90%

100%

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL W

ITH

IN M

OBIL

EW

ITH

IN M

OBIL

EW

ITH

IN M

OBIL

EW

ITH

IN M

OBIL

E

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

Residual LNAPL Fraction (unrecoverable)

Fraction of LNAPL Beyond Proposed Endpoint Range/was not Recovered

Fraction of LNAPL Beyond Proposed Recovery Endpoint/Continued to be Recovered with Significant Effort

Fraction of LNAPL Within Proposed Endpoint Range

8 years

10 years

8 years

0.6 years

2 years

0.6 years

12 years

13.5 years

>10 years>10 years>10 years>10 years - Estimated Time

>10 years - Elapsed Time

LNAPL Transmissivity vs Residual Fraction


0%

10%

20%

30%

40%

14 14 6 2 3.6 10 1.4 4.6 1.4 0.0015 - 0.0023 0.35

Well 7 Wells 8 - 21 Well 22 Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Wells 23 - 24 Well 25

Site 1 Site 2 Site 3 Site 4

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

FRAC

TIO

N O

F TO

TAL L

NAPL

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INTERVAL P

RIO

R T

O R

EC

OVERY E

FFO

RTS

(%)

INITIAL LNAPL TRANSMISSIVITY (FTINITIAL LNAPL TRANSMISSIVITY (FTINITIAL LNAPL TRANSMISSIVITY (FTINITIAL LNAPL TRANSMISSIVITY (FT2222/DAY)/DAY)/DAY)/DAY)

6 years 14 years11 years

11 years

11 years

2 years

3.75 years

2 years

10 years10 years10 years10 years


8 years7.5 years

4 years


NOTES:1. RECOVERABLE LNAPL VOLUMES ARE BASED ON DECLINE CURVE ANALYSIS, MASS BALANCE AND MODEL CALIBRATION2. RESIDUAL SATURATIONS ARE BASED ON SOIL CORE ANALYSES AND/OR MODEL CALIBRATION TO FIELD DATA

3. MODEL CALIBRATION INCLUDED, SOIL AND FLUID TYPE, AND LNAPL TRANSMISSIVITY DATA 21

Summary

• LNAPL transmissivity can be used as a start or stop metric for Maximum Extent Practicable (Source

Reduction via Hydraulic Recovery)

• Guidance has been improved over the past twelve years and provides a good foundation to

− Improve accuracy of LNAPL transmissivity estimates

− Provide multiple methods to estimate LNAPL transmissivity throughout the life of a site

• ITRC range combined with site LNAPL transmissivity data provides an absolute reference point for


• ITRC range combined with site LNAPL transmissivity data provides an absolute reference point for

hydraulic recovery/transmissivity values

• Sites exhibiting LNAPL transmissivity value below 0.8 ft2/day with existing recovery systems should

consider the effectiveness of continued hydraulic recovery in reducing remaining LNAPL source mass

22

Thank you

Andrew Kirkman, P.E.

Remedial Performance Application - Scenario 2

• Weak decline supports using individual well measurements (e.g., baildown tests) to measure LNAPL transmissivity across the plume


Graphics provided by

Remedial Performance Application - Scenario 1

• Strong decline indicates recovery system is well representative of capture zone


Graphics provided by

Documents

LNAPL Transmissivity End Points Why, How and When...LNAPL Transmissivity End Points Why, How and When Andrew Kirkman P.E. 1. LNAPL Transmissivity (Tn) ... − Or 80% recovery of a