USGS Groundwater Information: Hydrogeophysics Branch
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The USGS Office of Ground Water, Branch of Geophysics (OGW BG) is collaborating on an applied research project to evaluate the use of new hydrogeophysical tools to remotely monitor and visualize subsurface bioremediation amendment emplacement and transport in near real-time. The project, funded by the U.S. Department of Defense Environmental Security Technology Certification Program, could provide remediation project managers with a new, cost-effective solution to amendment monitoring during bioremediation.
Bioremediation is the use of biological methods, usually involving microorganisms, to break down or neutralize contaminants in soil, water, and wastes. Nutrients, oxygen, or other amendments may be added to stimulate or accelerate bioremediation and contaminant desorption from subsurface materials.
Bioremediation increasingly is selected as the remedy for sites with contaminated soil and (or) ground water. However, enhanced bioremediation is not successful unless the amendment reaches the target zone of contamination. Cleanup site managers have few tools that can provide them with near real-time information on the location of the amendment during and after emplacement. Current technologies typically rely on direct measurements in monitoring wells. These measurements are expensive and time consuming, often with a significant lag time between data collection and results delivery, and they provide only limited spatial and temporal information.
This project will demonstrate and evaluate an automated time-lapse geophysical data acquisition system that is coupled with automated data processing and results delivery. The system will be used to monitor the emplacement of the amendment in order to determine if it reached the intended areas and to monitor changes in the subsurface geochemistry associated with biodegradation (see Fig. 1).
Figure 1. Relationship between amendment injections, biological activity, and geophysical signatures. Amendments and biological activity result in changes to redox conditions, fluid chemistry, and hydraulic properties. These properties have geophysical signatures that can be monitored using radar, induced polarization (IP), self potential (SP), and electrical resistivity methods.
To accomplish these goals, the bioremediation monitoring system will automatically and in near real-time (see Fig. 2):
The system will reduce overall monitoring costs and increase monitoring performance by providing:
Figure 2. Project concept map. Field data are automatically collected and uploaded to remote server. At the server, data are checked, managed, and processed. Project scientists can view the data and results online anytime, from anywhere. Based on the results, they may modify the data collection and processing activities as needed.
The monitoring system will automatically record geophysical and conventional hydrological data collected at a demonstration field site at Brandywine Defense Reutilization and Marketing Office (DRMO), managed by Andrews Air Force Base in Maryland. Electrical-resistivity (ER), self potential (SP), induced polarization (IP), and borehole radar geophysical methods will be used. Hydrologic parameters such as redox, conductivity, temperature, and dissolved oxygen will be measured, and fluid samples will be collected for laboratory analysis.
Data will be uploaded automatically to computers at the Idaho National Laboratory, where automated analysis and processing of the geophysical data will create time-lapse three-dimensional (3D) images of subsurface electrical properties. These images and the associated data will be automatically posted online to allow project scientists to monitor and analyze the bioremediation effort remotely and in near real-time. Changes in the images over time will provide information on the distribution of the amendments, changes in the oxidation reduction potential (redox), and areas of precipitation/dissolution.
Figure 3. Fred Day-Lewis (USGS OGW Branch of Geophysics) prepares the on-site field office, where automated computer systems will record real-time geophysical data at the study area.
The project team installed a complex system of geophysical and hydrologic instrumentation at DRMO Area 2, where the Air Force will be conducting biostimulation in an effort to increase biodegradation of volatile organic compounds (VOCs) in ground water. In November 2007, a total of 19 wells were completed with the assistance of the USGS Wisconsin Water Science Center:
Soil samples and cone penetrometer, slug test, and electrical conductivity data were collected during well installation. Well construction allows for ongoing ground-water sampling at 56 points, and most of the wells also have thermistors and fluid specific conductance probes. In addition, four ERT surface cables and 30 porous pots for IP and SP were installed. A field office on site (see Fig. 3) houses the power supply, equipment control unit, computer, and a cellular modem, which will be able to collect thousands of measurements per hour and can be controlled remotely.
View the project photo gallery.
The project is funded by the U.S. Department of Defense (DoD) Environmental Security Technology Certification Program (ESTCP) with support from the USGS Toxic Substances Hydrology Program.
For more information on this project, please contact John W. Lane, Jr. (Chief, USGS OGW Branch of Geophysics) or Frederick Day-Lewis (Hydrologist, USGS OGW Branch of Geophysics), or call the Branch of Geophysics at (860)487-7402.