1. LNAPL Transmissivity (Tn) Remediation Design, Progress and Endpoints
Broad Brush – information dense slides, but we’ll cover much material quickly – handouts provide detail for reference
H2A Environmental, Ltd.
J. Michael Hawthorne, P.G.
September 2010

2. Outline LNAPL multi-phase fluid mechanics review LNAPL metrics review
Introduction
LNAPL multi-phase fluid mechanics review
LNAPL metrics review
LNAPL transmissivity (Tn) principles
Applicability
Summary
Outline

3. Non-Wetting Fluid (Air or LNAPL) Filling Large Pore Spaces
LNAPL at the Pore Scale
Multi-Phase Fluid Mechanics
Sediment Grains
Wetting Fluid (Water)
LNAPL co-exists with water in aquifer pores
LNAPL only partially fills the aquifer pore space
The degree of LNAPL saturation depends upon lithology and fluid properties
We now understand that LNAPL co-exists with water in the pore network within the aquifer. It does not float on the water table.
The degree of LNAPL saturation depends on the history, lithology, capillary parameters, and fluid properties of the site and the volume of LNAPL released. LNAPL only partially fills the aquifer pore space, and saturation decreases with depth until water fills all the pores.
The variation with depth of LNAPL saturation in the subsurface can be predicted when the properties of the subsurface media and fluid are known, and the apparent LNAPL thickness in the well is measured. This is accomplished by using the theories of Farr and McWhorter, and Lenhard and Parker. If sufficient measurements are taken across an LNAPL plume, the total volume of free LNAPL, its migration potential, and the recoverable volume also can be predicted. Spreadsheets (API Publication 4729) to perform these calculations have been made available by Randy Charbeneau for the API.
RTDF 2006
Non-Wetting Fluid (Air or LNAPL) Filling Large Pore Spaces

4. Ideal vs. Observed LNAPL Saturations
Saturation curve height = thickness of mobile LNAPL interval
Multi-Phase Fluid Mechanics
RTDF 2006

5. T vs. Tn / Tn vs. Sn Multi-Phase Fluid Mechanics
Transmissivity (T) for water
Unit cross-section, gradient, time
Aquifer thickness
Single fluid (krw drops out)
LNAPL Transmissivity (Tn)
Mobile LNAPL interval thickness
Multi-fluid (krn matters)
“How Much, How Fast”
Multi-Phase Fluid Mechanics

6. Ideal LNAPL Metric Collective property incorporates:
Aquifer properties (e.g., permeability)
Aquifer type (sand vs. clay)
LNAPL properties (e.g., viscosity)
LNAPL type (condensate vs. crude oil)
Fundamental or characteristic property
Repeatable
Saturation / mass driven
Easy and cheap to measure
LNAPL Metrics

7. Non-Ideal Metrics - Thickness
Same mass exhibits different thicknesses in different soil types
Inconsistent under varying hydrostatic conditions
LNAPL Metrics
Modified after Kirkman (2009)
Modified after RTDF (2006)

8. Non-Ideal Metrics – Recovery Data
Benefits
Direct measure of remediation performance
Provides predictive data for decline curve analysis
LNAPL Metrics
Problems
Strongly affected by system operational settings
Varies by technology – not directly comparable
Can’t be used to predict performance prior to startup

9. Tn – An Improved Metric LNAPL Metrics Tn Advantages
Direct numeric measure of hydraulic recoverability
Varies directly with LNAPL saturation / mass
Normalizes all sites to a single measurement standard
Multiple Methods
Measurable prior to, during and after remediation

10. LNAPL Transmissivity (Tn)
Analog to aquifer transmissivity
Provides basis for mobility / recoverability analyses
Four measurement methods
Baildown / skimming tests
Recovery data analysis
skimming
Vacuum enhanced skimming
Total fluids pumping
Multi-phase extraction
Physical properties / modeling
Tracer tests
Hydraulic recovery only
Dissolved and vapor phase risk issues are separate
Transmissivity (Tn) Principles

11. Applicability – Uses for Tn
Alternative to laboratory Sn
Model calibration parameter
Technical impracticability threshold
Remediation design parameter
Operational progress metric
Recovery end point
Applicability

12. Applicability - TI Demonstration
Technical Impracticability (TI) requires either:
Recovery system data
“Can I please turn it off now?”
Direct recoverability threshold metric
Data from a pilot test and modeling study
“Can I please not turn it on?”
Robust calibration parameter for TI modeling
Applicability

13. Applicability – Remediation Design
Remediation design parameter
Compare different technologies (calibrated model)
Technology-specific production curves
Predicted rate and total volume decline curve analyses
Sustainability
Design parameters
Equipment sizing
Waste management / recycling volumes
Design cost-benefit analysis
Projected operational lifetime
Capital vs. mobile infrastructure
Applicability

14. Applicability – Operational Progress
Operational Progress Metric
Recovery data decline curve analysis (progress towards endpoint)
Non-recovery wells to monitor plume progress to endpoint
Applicability

15. Tn Endpoint Analysis Hydraulic recovery end point (0.3 to 0.8 ft2/day)
Applicability
(Kirkman 2010)

16. Tn Endpoint Analysis
Applicability

17. Summary Summary Tn is an improved metric for hydraulic recoverability
Four calculation methods:
Baildown / manual skimming testing
Recovery data analysis
Physical properties analysis
Tracer testing
Tn use as a metric
Indirectly as a robust model calibration parameter
Directly as a recoverability threshold ( ft^2/day)
Remediation and Tn
TI threshold
Design parameter
End point for hydraulic recovery
Summary