Investigating the Sensitivity of Emerging Geophysical Technologies to Immobile Porosity and Isolated DNAPL and Dissolved/Sorbed VOC Mass in Fractured Media

Dr. Lee Slater | Rutgers University-Newark

ER-2421

Objective

Dense nonaqueous phase liquid (DNAPL) contamination of fractured rock remains a long-term, persistent Department of Defense (DoD) problem. The diffusion of aqueous phase contaminant into low-permeability matrix blocks between fractures, or in and from dead-end fractures, limits the efficiency of fractured-aquifer remediation by conventional and alternative engineered remediation. Understanding this fine-scale distribution of contaminant mass away from fractures, and how this mass changes in response to remediation efforts, is critical for improving remediation operation in fractured rock settings. The primary objectives of this research are to:

  1. Determine the sensitivity of emerging borehole geophysical technologies to immobile porosity and DNAPL and aqueous-phase contaminant mass isolated within the immobile porosity of fractured rock that is typically inaccessible to aqueous sampling techniques.
  2. Evaluate the predictive capabilities of these geophysical technologies with respect to quantifying immobile porosity and/or contaminant mass concentration.
  3. Obtain better information at high spatial resolution on the distribution of contaminant mass within the immobile porosity of a fractured rock in relation to the location of the primary fractures governing flow/transport.
ER-2421_project_graphic

Field data collection of borehole Nuclear Magnetic Resonance (NMR) at the former Naval Air Warfare Center (NAWC) in West Trenton, NJ.

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Technical Approach

This project will determine the sensitivity of two emerging geophysical technologies—nuclear magnetic resonance (NMR) and complex resistivity (CR)—to immobile porosity and contaminant mass in the immobile pore space. The technical approach includes: (1) fine-scale delineation of contaminant mass around fractures using a discrete fractured network (DFN) approach, (2) fine-scale delineation of porosity from core samples acquired as part of the DFN, (3) borehole and laboratory measurements with NMR and CR with sensitivity to immobile porosity and contaminant mass at high spatial resolution, and (4) pore-scale modeling to quantitatively link geophysical responses to the distribution of contaminant mass. Measurements will be performed at the Naval Air Warfare Center (NAWC), West Trenton, New Jersey; Edwards Air Force Base, located in Southern California; the Pease International Tradeport (the former Pease Air Force Base), Portsmouth, New Hampshire; and the Santa Susana Field Laboratory (SSFL) in Southern California. This approach will permit both assessment of fine-scale contaminant mass around fractures and geophysical method performance across a range of geological settings from clastic to crystalline fractured rock, spanning the east to west coasts of the United States.

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Benefits

This work will determine relationships between measurements obtained from two emerging geophysical technologies in fractured rock settings and the following properties: (1) immobile porosity, and (2) contaminant mass in the immobile pore space. Having established such relations, the geophysical technologies could be employed to efficiently monitor the effectiveness of multiple existing remedial technologies (e.g., bioremediation, thermal treatment, monitored natural attenuation, chemical addition) in reducing contaminant mass in the rock matrix, particularly adjacent to hydraulically active fractures. The geophysical measurements could be repeatedly deployed in a borehole at a fraction of the cost of conventional sampling methods that rely on direct quantification of mass from cores. Such monitoring data could provide early information to help predict the long-term performance of remedial technologies and aid in decision-making, with respect to discontinuation of a technology or implementation of an alternative. Furthermore, this work will provide new information on the fine-scale distribution of contaminant mass around fractures in four fractured rock sites of DoD concern. Information gained from this project was used to inform ESTCP project ER-201118. (Anticipated Project Completion - 2019)

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Publications

Robinson, J., Slater, L., Weller, A., Keating, K., Robinson, T., & Parker, B. (2018). On Permeability Prediction from Complex Conductivity Measurements Using Polarization Magnitude and Relaxation Time. Water Resources Research. doi:10.1002/2017WR022034

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Points of Contact

Principal Investigator

Dr. Lee Slater

Rutgers University-Newark

Phone: 973-353-5109

Fax: 973-353-1965

Program Manager

Environmental Restoration

SERDP and ESTCP

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