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LNAPL Transmissivity (T n ) Remediation Design, Progress and Endpoints

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

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  1. LNAPLTransmissivity (Tn)Remediation Design, Progress and Endpoints H2A Environmental, Ltd. J. Michael Hawthorne, P.G. mhawthorne@h2altd.com www.h2altd.com September 2010

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

  3. 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

  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 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

  6. 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

  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

  10. 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

  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 Applicability • 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

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

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