1. A Subsidiary of GEI Consultants, Inc.
Selection of an Optimal Site-Specific Method for the Measurement of LNAPL Transmissivity
J. Michael Hawthorne, PG
H2A Environmental, Ltd.
A Subsidiary of GEI Consultants, Inc.

2. Three Short Term LNAPL Transmissivity Measurement Methods are Available in ASTM E2856 Guidance for the Measurement of LNAPL Transmissivity
Hawthorne, J. Michael (2013) LNAPL Transmissivity from Total Fluids Recovery Data, Part 1: Calculation Methodology, Applied NAPL Science Review, vol. 3, issue 2, February 2013

3. What are baildown testing, manual skimming testing, and oil/water ratio testing?
Baildown/Slug Test
Manual Skimming Test
Oil/Water Ratio Test
Hawthorne, J. Michael (2010) LNAPL Transmissivity (Tn): Remediation Design, Progress and Endpoints, Texas Commission on Environmental Quality Annual Trade Fair and Conference, May 2010

4. Generalized LNAPL Transmissivity Testing Dynamics
Remove Fluids to Create Pressure Head Differential
Quantify Recharge Rate & Drawdown (Gauging, Qn, or OWR)
Calculate LNAPL Transmissivity

5. A recent API nationwide statistical analysis of LNAPL transmissivity found that all methods except petrophysical calculation appear to generate similar (repeatable) values (insufficient data for slug testing)
Hawthorne, J. Michael, Dennis Helsel and Charles Stone (2015) Nationwide Statistical Analysis of LNAPL Transmissivity, unpublished research conducted by H2A Environmental, Ltd. on behalf of The American Petroleum Institute

6. ASTM E2856-13 guidance for Tn test method selection, modified
Factor
Baildown (BD) Test
Manual Skimming (MS)
Oil/Water Ratio (OWR)
Waste Disposal
Minimal
Moderate
Large
Aquifer Extent
Small
Moderate – Large
Capital Cost
Low
Low – Moderate
Test Duration
Minutes – Months
Minutes – Days/Weeks
Minutes – Hours
SC1:
sn sensitive
Can be sn insensitive
SC2:
Equilibrium required
Equilibrium optional
SC3:
Recommend ANT>0.5 foot; Require ANT>0.2 foot
Works with any measurable ANT
SC4:
Any hydrogeologic condition
Any hydrogeologic condition (Adjust calc for perched)
Power (air, electricity, etc.)
Useful but not necessary
Preferred but not necessary
Required
See ASTM E for a more detailed discussion

7. Groundwater Fluctuations
Critical variables I’ll focus on today in the selection of an optimal site-specific test methodology for LNAPL transmissivity
Barometric Pressure
Tides
Pumping
Rainfall / Recharge
River Fluctuations
Groundwater Fluctuations
NAPL Drawdown
NAPL Viscosity
Transient Aquifer Property
NAPL Physical Property
Temperature
NAPL Density

8. The NAPL hydrogeologic condition can strongly affect the ANT in the well, requiring correction to determine the MNI

9. What is NAPL Drawdown?
Hawthorne, J. Michael (2014) Calculating NAPL Drawdown, Applied NAPL Science Review, vol. 4, issue 3, September 2014

10. ASTM 2011, Equation 9:
𝑠 𝑛𝑡 = 𝑍 𝐴𝑁 ∗ − 𝑍 𝐴𝑁(𝑡)
for snt ≤ ZAN* ̶ Zpc
Where:
snt = NAPL drawdown at time t
ZAN* = air/NAPL interface elevation
for equilibrium conditions
ZAN(t) = air/NAPL interface elevation at
time t
Zpc = NAPL/perching layer contact
elevation

11. ASTM 2011 Equation 11 (generalized confined drawdown equation):
𝑠 𝑛𝑡 = 𝑍 𝐴𝑁 ∗ − 𝑍 𝑐𝑐 𝜌 𝑛 − 𝑍 𝑁𝑊 𝑡 − 𝑍 𝑐𝑐 𝜌 𝑤 − 𝑍 𝐴𝑁(𝑡) − 𝑍 𝑁𝑊(𝑡) 𝜌 𝑛 𝜌 𝑛
Where:
snt = NAPL drawdown at time t
ZAN* = the air/NAPL interface elevation for
equilibrium conditions
Zcc = NAPL/confining layer contact elevation
ZNW(t) = NAPL/water interface elevation at time t
ZAN(t) = air/NAPL interface elevation at time t
ρn = NAPL density
ρw = water density

12. ASTM 2011 Equation 10 (simplified confined drawdown equation):
𝑠 𝑛𝑡 = 𝑏 𝑛𝑓 1− 𝜌 𝑟 𝜌 𝑟
Where:
snt = NAPL drawdown at time t
bnf = mobile NAPL interval thickness in
the formation (not the same as the
gauged apparent NAPL thickness)
ρr = NAPL/water density ratio

13. What is the frequency and magnitude of unconfined LNAPL?
Hawthorne, J. Michael, Dennis Helsel and Charles Stone (2015) Nationwide Statistical Analysis of LNAPL Transmissivity, unpublished research conducted by H2A Environmental, Ltd. on behalf of The American Petroleum Institute

14. What are realistic Ranges of NAPL Drawdowns for unconfined NAPL?

15. Why is manual skimming sensitive to sn?
Generally safe to assume ln(Roi/rw) = 4.6, so equation simplifies to:
Batch extract NAPL “continuously” until:
All NAPL removed from filter pack
NAPL production from well represents formation flow
NAPL production stabilizes
Gauge Air/NAPL interface frequently throughout the test to document drawdown for calculations
Each “batch” stabilized NAPL production rate along with the corresponding drawdown is used to calculate Tn
Even if Tn cannot be accurately calculated, the stabilized production rates and drawdowns provide valuable CSM and design information
Gauge recharge of NAPL into the well after test completion to generate a discharge vs. drawdown plot
𝑇 𝑛 = 𝑄 𝑛 𝑠 𝑛
Hawthorne, J. Michael (2014) LNAPL Transmissivity (Tn): Remediation Design, Progress and Endpoints, Texas Commission on Environmental Quality Annual Trade Fair and Conference, May 2010
Charbeneau, Randall (2007) LNAPL Distribution and Recovery Model Volume 1: Distribution and Recovery of Petroleum Hydrocarbon Liquids in Porous Media, Publication No. 4760, The American Petroleum Institute

16. Hawthorne, J. Michael, Dennis Helsel and Charles Stone (2015) Nationwide Statistical Analysis of LNAPL Transmissivity, unpublished research conducted by H2A Environmental, Ltd. on behalf of The American Petroleum Institute

17. What are some common conditions that help or hurt the ability to accurately measure Tn?
“Helpful” Conditions (any method)
“Hurtful” Conditions (OWR beneficial)
Low density LNAPL
High density LNAPL
Low dynamic viscosity
High dynamic viscosity
High NAPL saturation
Low NAPL saturation
High hydraulic conductivity
Low hydraulic conductivity
Rapid NAPL recharge (short time)
Slow NAPL recharge (long time)
SUM: High Tn with low density
SUM: Low Tn with high density
Small relative groundwater fluctuations
Large relative groundwater fluctuations

18. Type curves to analyze and plan Tn testing
Charbeneau, Randall, Andrew J. Kirkman and Rangaramanujam Muthu (2012) LNAPL Transmissivity Baildown Spreadsheet, Draft API Publication
Type curves to analyze and plan Tn testing

19. Keys to selecting the “optimal” site-specific Tn measurement method
Know the NAPL hydrogeologic condition
Understand your objective – absolute or relative value for Tn?
Know Groundwater Fluctuation Duration and Magnitude
Use method with small duration relative to GW fluctuation duration
Use method with large sn relative to GW fluctuation magnitude over the test duration
If ANT<0.5 foot, consider OWR testing then MS (not BD)
Critical zone is low Tn with high density and small ANT