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Ground Water Sampling and Geophysical Methods Development and Evaluation

Abstract:

Inadequate site characterization and a lack of knowledge of subsurface contaminant distributions (particularly non-aqueous phase liquids [NAPLs]) hinder our ability to make good decisions on remediation options and to conduct adequate cleanup efforts at contaminated sites. Noninvasive (i.e., no drilling or sampling required) geophysical techniques can provide methods for subsurface site characterization and monitoring of organic contamination in a rapid, cost-effective, safe manner, and provide a method for evaluating the success of remediation efforts. Research is being conducted to improve and evaluate the resolution of the complex resistivity (CR), natural potential (NP), electromagnetic (EM), seismic, and ground penetrating radar (GPR) methods over complex geological formations. Prototype instruments and computer software for interpretation of the results are being developed and evaluated. Laboratory experiments are being conducted to determine the geophysically relevant changes which occur during surfactant enhanced aquifer remediation of tetrachloroethylene (PCE). A prototype high resolution in situ geophysical probe is being tested, along with a data acquisition system, for deployment at hazardous waste sites. In conjunction with the U.S. Navy, a test cell is being planned for use in controlled spill experiments at Port Hueneme, Naval Base Ventura County, California.

Objective:

Research is being conducted to improve and evaluate the resolution of the CR, EM, seismic, and GPR methods over complex geological formations (such as fractured geologies) and to evaluate the capability of these geophysical methods to delineate subsurface organic contaminants. Methods to monitor the effectiveness of remediation technologies, beginning with surfactant enhanced aquifer remediation, are being investigated. In situ geophysical tools, along with data acquisition systems, are being developed and tested for use at hazardous waste sites.

Progress to Date:

A site was identified at the Lawrence Berkeley National Laboratory (LBNL) where an existing nonmetallic tank (approximately 5 meters by 3 meters by 2 meters deep) was utilized in conjunction with ongoing research at LBNL. A fiberglass tank, about 3 meters in diameter and 2 meters deep, was placed inside the rectangular tank as an additional barrier against any possible tetrachloroethylene (PCE) leakage. Controlled PCE spill experiments using cross-borehole seismic and complex resistivity methods were conducted in smaller cylinders and intermediate size tanks (100 cm by 50 cm by 40 cm) with sand and sand/clay lenses in order to develop the geological criteria and procedures for the spill experiment in the larger fiberglass tank. Based upon these results, geological formations were constructed in the fiberglass tank consisting of five layers of sand and sandy clay lenses utilizing about 28,000 pounds of clean, well-sorted 20/30 Unimin sand and 92 pounds of well-characterized calcium montmorillonite clay obtained from the Clay Repository. After monitoring the stabilization of the physical properties of the geological formations for 2 months, a controlled PCE spill experiment was conducted during May 2004. Over a 26-hour period, a total of 85 liters of PCE was injected at a depth of about 6 cm into the center of the fiberglass tank. Geophysical monitoring of the tank was obtained before, during and after the PCE injection with a total of 10 different geophysical methods: borehole and cross-borehole complex resistivity (CR), cross-borehole seismic tomography (ST), surface high frequency electromagnetic system (HFEM), surface very early time electromagnetic system (VETEM), borehole dielectric logging tool (BDL), directional borehole ground penetrating radar (DBGPR), cross-borehole GPR, surface GPR, self-potential, and down hole video logging. Preliminary analysis indicated that the PCE broke through to the bottom of the tank within 4 hours after the start of the injection. About 80 percent of the PCE was at the bottom of the tank within a day after the injection stopped. The PCE came in direct contact with the complex resistivity borehole probes and destroyed a number of electrodes; hence, long-term monitoring could not continue beyond 2 months. The tank was remediated, excavated, and samples were obtained throughout the formations for GC analysis of residual PCE concentrations. The results are being correlated with the residual geophysical anomalies.

After the sand was remediated to a clean state (no detectable PCE, <1 ppb), the formations were reconstructed with slightly different clay content and design. A second PCE injection experiment was conducted in September 2005. The injection rate was considerably reduced from the first experiment. Over a period of 72 hours, a total of 23.5 liters of PCE was injected at a depth of 6 cm into the center of the tank. Geophysical monitoring was obtained before, during, and after the PCE injection with eight different geophysical methods: cross-borehole seismic tomography, borehole and cross-borehole complex resistivity, surface ground penetrating radar, cross-borehole radar, surface high frequency electromagnetic system, borehole dielectric logging, borehole self potential, and borehole video logging. Data from this experiment are currently being analyzed.

A final design has been completed for a characterization test cell (CTC) to be built at Naval Base Ventura County in Port Hueneme, California. The CTC is a nonmetallic (concrete with geomembrane liners) tank to be used for controlled spill experiments. A Memorandum of Understanding has been drafted to be signed by the Navy and EPA regarding the location and operation of the CTC at an existing SERDP test facility on the base in Port Hueneme. This cell would be constructed to allow for research on ground water movement and sampling for DNAPLs and will be used for geophysical research under this task.

Laboratory experiments continue to determine the geophysically relevant changes which occur during surfactant-enhanced aquifer remediation of PCE. The experiments to date are being completed in the aqueous phase with different geologic matrixes (i.e., sand, clay, sand + clay mixture) added in future experiments. Response surface methodology has been selected and developed for the experimental design. Two categorical factors and one numerical factor are varied to determine the changes in the conductivity, DO, pH, and density. Upon completion of this phase of experimentation, a different matrix will be added, then progressing to column experiments measuring various geoelectrical properties and acoustic properties.

Sponsorship (via small grant) to the Environmental and Engineering Geophysical Society for the compilation and production of the CD-ROM proceedings from their annual conference, "The Symposium on the Application of Geophysics to Environmental and Engineering Problems 2005 (SAGEEP 05)," was successfully awarded. The meeting was held in Atlanta, GA, and included technical presentations and workshops on the utility of geophysics to environmental and engineering needs.

Sponsorship (via small grant) to the American Geophysical Union Spring 2006 meeting in New Orleans, LA, was awarded. This meeting focused on biogeophysics, which involves the interdisciplinary study of biology and geophysics. Specifically, the meeting promoted and furthered the development of this new science of using geophysics to detect and monitor biological activity and processes.

A prototype high resolution in-situ probe was built and has passed initial laboratory testing and evaluation. It is planned this upcoming year will finalize the laboratory evaluation, begin field testing, and include a patent application. In concert with this in-situ probe development is the design, engineering, assembly, and testing of a remote automated acquisition system. Preliminary design has been completed and the assembly and initial software development are ongoing via a student services contract. This instrument will continue development throughout FY06 and should also follow with a patent application.

Relevance/Significance/Impact:

The activity supports the ORD's Long Term Goals and Objectives #3 in the 1997 Update to ORD's Strategic Plan. This goal, "to provide common sense cost-effective approaches for preventing and managing risks," is covered by research conducted under this task in the specific area of developing cost-effective techniques for characterizing and remediating soils and ground water contaminated with non-aqueous-phase liquids, chlorinated and other hazardous organics and toxic metals. In addition, the projects are related to the high importance, ORD high priority research areas of contaminated sites—ground water, soils, and sediments. In the Strategic Plan 2000, research conducted under this task is described in the research priority entitled, "Research to Improve Eco-System Risk Assessment/Management - Monitoring Research. This research is a high priority also as described in the ORD Waste Research Plan. When successfully and fully developed, the noninvasive geophysical techniques will allow for the rapid identification of the location of spilled NAPLs and chlorinated solvents at costs much below the costs associated with conventional sampling and laboratory analyses. The developed techniques will allow for real time monitoring of contaminant distributions and their potential movement in the subsurface.

Research conducted under this task directly supports OSRTI, OSW, the Regions, and other users, such as the states and other federal agencies, by providing improved methods, techniques, and tools to detect spilled contaminants in the subsurface without the necessity of drilling and collecting samples for subsequent laboratory analysis. Some of the geophysical investigations described in this task are performed in partnership with the premier geophysics researchers from the U.S. Geological Survey and the Department of Energy's Lawrence Berkeley National Laboratory. This research program is reviewed annually during the Waste Progress Review held in Washington, DC, with OSRTI, OSW, Regions, and other interested program offices. The current and proposed future studies support the OSRTI high priority research need entitled, "Ground Water DNAPL Site Characterization" as identified by OSRTI staff and in the Contaminated Sites Multi-Year Plan. The research in this task has been rated as the highest priority in the recent 2005 OSWER research needs by both the Ground Water and Site Characterization Regional Research Advisory Workgroups. It is through these reviews and communication with the client offices that ESD-LV ensures that we are meeting their wants, needs, expectations, and requirements now and in the future.

In the ORD Contaminated Sites Multi-Year Plan and 2004 Contaminated Sites Multi-Year Research Overview, the research for this task is described under the "Ground Water" long-term goal (Long Term Goal #2).

Approach:

FY06 Activities:

The work planned in FY06 can be separated into six parts: (1) continue the analysis of the May 2004 and September 2005 PCE injection experiments in the fiberglass tank, (2) evaluate the capability of geophysical methods to monitor the remediation of PCE, (3) start construction of the second, larger test cell at Port Hueneme, California, (4) evaluate the use of the proton resonance sounding geophysical method for site characterization, (5) design and construction of a prototype in situ high resolution remote monitoring system, and (6) sponsorship of relevant scientific symposia.

(1) Interpretation, modeling, and a comparison of the geophysical responses of the two spill experiments at LBNL will continue and articles on the results of the PCE spill experiments will be written for submission to peer-review journals. Initial efforts will be put forth into examining the effectiveness of the borehole dielectric logging technique, seismic tomography, high frequency and transient electromagnetic techniques, and complex resistivity techniques in monitoring the movement of PCE through the soil.

Laboratory and intermediate size tank experiments will be continued on evaluating remediation methods that may be applied to the larger fiberglass tank and characterization test cell. Long term monitoring or the second PCE injection in the fiberglass tank with complex resistivity, GPR, seismic tomography, and borehole video logging will continue until the tank is remediated in the spring of 2006. During remediation, soil samples will be collected to determine the PCE concentration throughout the different layers, thereby, providing a basis to evaluate the effective PCE detection limits for the different geophysical methods.

The Geophysical Advisor Expert System computer program, version 3.0, will be updated with the results from the various controlled DNAPL spill experiments.

(2) Experiments to investigate, model, and predict the geophysical response to surfactant remediation of PCE will continue in complexity beyond the aqueous phase. Various matrix materials will be added as well as column experiments with variable saturation levels. The acquisition of new equipment is planned to enable complex resistivity and acoustic property measurements in laboratory column experiments.

(3) A site for a second controlled spill test cell has been located at the U.S. Navy's Naval Base Ventura County (NBVC), in Port Hueneme, California. This location is also the site of an SERDP national test site that is used for characterizing and remediating soils, sediments, and ground water contaminated with fuel hydrocarbons and waste oil using in-situ and ex-situ techniques. An interagency agreement has been put in place with the U.S. Navy to construct the characterization test cell and construction is anticipated to start in the spring of FY06.

(4) A new surface geophysical technique, the proton resonance sounding method, for determining subsurface water content and permeability will be evaluated by conducting field tests in Southern Nevada and comparing the results to borehole cores and logging. This technique may provide a new tool for noninvasive subsurface characterization at hazardous waste sites.

(5) An in-situ probe patent application will be completed and the laboratory testing of the prototype will be finalized. Improvements to the prototype are to be determined and the next version designed and built for continued laboratory and field testing. The remote acquisition system for the in-situ probe will continue its prototype evolution and reach the stage of patent application and laboratory testing.

(6) Sponsorship (via small grant) to the Environmental and Engineering Geophysical Society will continue as in years past. Unique to FY06 will be the production of a compilation Special Contaminant Studies CD-ROM. This CD-ROM will compile all the past papers (since 1988) presented at SAGEEP and relevant to contaminant studies or those which meet EPA’s mission. This CD-ROM will be presented to conference attendees and then sent via mass-mailer to EPA Regions and interested parties. The 2006 Symposium is being held in Seattle, WA.

FY07 Activities:

The Geophysical Advisor Expert System computer program, version 3.0, will continue being updated with the results from the various controlled DNAPL spill experiments.

The identification of field sites to complement the laboratory understanding of geophysically monitoring surfactant remediation of PCE is to be completed. It is anticipated that this field application will lead to a case history report.

Experiments in the CTC at Port Hueneme will be initiated in FY07 and may include reexamining the effectiveness of the resolution of the complex resistivity, natural potential, electromagnetic, seismic, and ground penetrating radar methods to directly detect the subsurface PCE (or some other chlorinated solvent) in a different environment and the initial tests to evaluate the performance of new and innovative samplers for DNAPL-contaminated ground waters. A series of sample locations, in a gridded array (called a Latin square) with five samplers of each type, would be used to evaluate the performance of new and innovative samplers being used for ground water monitoring. Water with known amounts of DNAPL will be circulated through the artificial aquifer to minimize outside influences on the sampling results.

Field testing and evaluation of the high resolution in situ site monitoring system at the CTC in Port Hueneme and at Regional sites is to be determined in FY07 and subsequent years. The field component in FY07, and beyond, is aimed at testing the utility of the system as a sensor for the detection and monitoring of subsurface processes at both contaminated and uncontaminated sites, as well as in a variety of other related applications. Some of these other applications would be: measurement of changes in the vertical temperature profile; salt-water intrusion studies; infiltration rate research (which may include flow-through rates of fertilizers, pesticides and herbicides in agricultural lands, for example); and changes in soil structure and properties subsequent to deforestation. The testing of the system will evaluate the utility of the system for Regional Project Managers and identify improvements and areas for further design and development.

FY08 Activities:

The geophysical monitoring of the PCE spill in the CTC at Port Hueneme will continue into FY08. Interpretation, modeling, and a comparison of the geophysical responses of this spill will be initiated. Upon completion of the monitoring, samples will be collected and analyzed using standard GC/MS techniques to "ground truth" the results from the various geophysical techniques being employed. Interpretive software may need to be adjusted based upon the results of the received signals and the ground truthing efforts.

Development of the long term understanding and model of the remote monitoring results from the in situ system will begin. During FY07, the analysis and data management from the in situ probe data will be developed from controlled spills at the CTC and regional site locations.

Development of several robust in situ monitoring systems for further deployment at regional sites as a tool for project managers to aid in their decision making and site monitoring goals will be initiated.

The Geophysical Advisor Expert System computer program, version 3, will continue to be updated with the results from the various experiments conducted in the controlled test cell.

Staffing

Principal Investigators:

Aldo Mazzella, Geophysicist
Steven Gardner, Geologist
Dale Werkema, Env. Scientist

Other Researchers:

John Zimmerman, Research Physical Scientist

Products:

Abstracts and Oral Presentations:

Mazzella, A.T. “Electrical Resistivity Variations Associated With Controlled Gasoline Spills.” Presented at 36th Annual Engineering Geology & Geotechnical Engineering Symposium, Las Vegas, NV, March 28-30, 2001.
Date Cleared:	3/26/2001	Date Presented:	3/28/2001	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 01-044

Mazzella, A.T. “Electrical Resistivity Variations Associated With Controlled Gasoline Spills.” Presented at Society of Exploration Geophysicist/Calgary 2000 International Exposition and 70th Annual Meeting, Calgary, Canada, August 6-11, 2000.
Date Cleared:	3/21/2000	Date Presented:	8/6/2000	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 00-088

Werkema, D., E. Atekwana, E.A. Atekwana, S. Rossbach, and W. Sauck. “Laboratory and Field Results Linking High Conductivities to the Microbial Degradation of Petroleum Hydrocarbons.” Presented at Symposium on the Application of Geophysics to Environmental and Engineering Problems, Colorado Springs, CO, February 22-26, 2004.
Date Cleared:	8/26/2003	Date Presented:	2/22/2003	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 03-121

Werkema, D., E. Atekwana, E.A. Atekwana, S. Rossbach, and W. Sauck. “Geoelectrical Evidence of Microbial Degradation of Diesel Contaminated Sediments.” Presented at Fall American Geophysical Union Meeting, San Francisco, CA, December 8-12, 2003.
Date Cleared:	8/26/2003	Date Presented:	12/8/2003	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 03-120

Werkema, D., E. Atekwana, A. Endres, and W. Sauck. “Geoelectrical Stratigraphy and Analysis of a Hydrocarbon Impacted Aquifer.” Presented at Joint Assembly of the European Geophysical Society, and the American Geophysical Union and European Union of Geosciences Spring 2003 Meeting, Nice, France, April 4-13, 2003.
Date Cleared:	1/22/2003	Date Presented:	4/4/2003	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 03-006

Werkema, D., E. Atekwana, J.W. Duris, and S. Rossbach. “Microbial Community Structure in a Shallow Hydrocarbon-contaminated Aquifer Associated With High Electrical Conductivity.” Presented at Joint Assembly of the European Geophysical Society, and the American Geophysical Union and European Union of Geosciences Spring 2003 Meeting, Nice, France, April 4-13, 2003.
Date Cleared:	1/22/2003	Date Presented:	4/4/2003	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 03-005

Werkema, D., Atekwana, E., Atekwana, E.A., Rossbach, S., Sauck, W., and Sherrod, L. “Geoelectrical Evidence of Microbial Degradation of Diesel Contaminated Sediments.” Presented at Fall American Geophysical Union Meeting, San Francisco, CA, December 8, 2003.
Date Cleared:	12/3/2003	Date Presented:	12/8/2003	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 03-159

Abraham, J.D., A. Legtchenko, A.T. Mazzella, E. White, and J.B. Fleming. “TDEM and NUMIS^(PLUS) Soundings at the Ash Meadows National Wildlife Refuge: A Case Study.” Presented at 2nd International Workshop on the Magnetic Resonance Sounding Method Applied to Non-Invasive Groundwater Investigations, Orleans, France, November 19-21, 2003.
Date Cleared:	11/12/2003	Date Presented:	11/19/2003	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 03-145

Werkema, D., E. Atekwana, E. Atekwana, J.W. Duris, S. Rossbach, J. Allen, and W. Sauck. “Laboratory and Field Results Linking High Bulk Conductivities to the Microbial Degradation of Petroleum Hydrocarbons.” Presented at 2004 Symposium on the Applications of Geophysics to Environmental and Engineering Problems, Colorado Springs, CO, February 22-26, 2004.
Date Cleared:	2/19/2004	Date Presented:	2/22/2004	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 04-034

Werkema, D. “Indirect Measurement of Biological Activity to Monitor Natural Attenuation.” Presented at EPA Science Forum 2004, Washington, DC, June 1-3, 2004.
Date Cleared:	3/1/2004	Date Presented:	6/1/2004	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 04-087

Werkema, D. “Indirect Measurement of Biological Activity to Monitor Natural Attenuation.” Presented at EPA Science Forum 2004, Washington, DC, June 1-3, 2004.
Date Cleared:	5/17/2004	Date Presented:	6/1/2004	Peer Review Category:	4
Tracking ID:	nerl-lv-ESD 04-113

Mazzella, A. “Evaluation of Geophysical Methods for the Detection of Subsurface Tetrachloroethylene (PCE) in Controlled Spill Experiments.” Presented at EPA 2005 Science Forum, Washington, DC, May 16-18, 2005.
Date Cleared:	2/1/2005	Date Presented:	5/16/2005	Peer Review Category:	3
Tracking ID:	nerl-lv-ESD 05-020

Werkema, D.D., E. Atekwana, E. Atekwana, S. Rossbach, J. Duris, J. Allen, L. Smart, and W. Sauck. “Monitoring Hydrocarbon Biodegradation With DC Resistivity.” Presented at Application of Geophysics to Environmental & Engineering Problems, Seattle, WA, April 02-06, 2006.
Date Cleared:	10/31/2005	Date Presented:	11/2/2006	Peer Review Category:	3
Tracking ID:	nerl-lv-ESD 05-153

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