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LNAPL Transmissivity (T n ) Remediation Design, Progress and Endpoints. H 2 A Environmental, Ltd . J. Michael Hawthorne, P.G. mhawthorne@h2altd.com www.h2altd.com September 2010. Outline. Introduction. LNAPL multi-phase fluid mechanics review LNAPL metrics review

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lnapl transmissivity t n remediation design progress and endpoints

LNAPLTransmissivity (Tn)Remediation Design, Progress and Endpoints

H2A Environmental, Ltd.

J. Michael Hawthorne, P.G.



September 2010



  • LNAPL multi-phase fluid mechanics review
  • LNAPL metrics review
  • LNAPL transmissivity (Tn) principles
  • Applicability
  • Summary
lnapl at the pore scale
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

RTDF 2006

Non-Wetting Fluid (Air or LNAPL) Filling Large Pore Spaces

ideal vs observed lnapl saturations
Ideal vs. Observed LNAPL Saturations

Saturation curve height = thickness of mobile LNAPL interval

Multi-Phase Fluid Mechanics

RTDF 2006

t vs t n t n vs s n
T vs. Tn / Tn vs. Sn

Transmissivity (T) for water

Unit cross-section, gradient, time

Aquifer thickness

Single fluid (krwdrops out)

LNAPL Transmissivity (Tn)

Unit cross-section, gradient, time

Mobile LNAPL interval thickness

Multi-fluid (krnmatters)

“How Much, How Fast”

Multi-Phase Fluid Mechanics

ideal lnapl metric
Ideal LNAPL Metric

LNAPL Metrics

  • 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
non ideal metrics thickness
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)

non ideal metrics recovery data
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
lnapl transmissivity t n
LNAPL Transmissivity (Tn)

Transmissivity (Tn) Principles

  • 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
applicability uses for t n
Applicability – Uses for Tn

Alternative to laboratory Sn

Model calibration parameter

Technical impracticability threshold

Remediation design parameter

Operational progress metric

Recovery end point


applicability ti demonstration
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 remediation design
Applicability – Remediation Design

Remediation design parameter

Compare different technologies (calibrated model)

Technology-specific production curves

Predicted rate and total volume decline curve analyses


Design parameters

Equipment sizing

Waste management / recycling volumes

Design cost-benefit analysis

Projected operational lifetime

Capital vs. mobile infrastructure


applicability operational progress
Applicability – Operational Progress

Operational Progress Metric

Recovery data decline curve analysis (progress towards endpoint)

Non-recovery wells to monitor plume progress to endpoint


t n endpoint analysis
Tn Endpoint Analysis

Hydraulic recovery end point (0.3 to 0.8 ft2/day)


(Kirkman 2010)



  • 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 (0.3-0.8 ft^2/day)
  • Remediation and Tn
    • TI threshold
    • Design parameter
    • End point for hydraulic recovery