Impact/Purpose:

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.

Description:

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. Non-invasive (i.e., no drilling or sampling is 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 (such as fractures). Prototype instruments and computer software for interpretation of the results are being developed and evaluated.

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Record Details:

Record Type:PROJECT

Start Date:10/01/1997

Projected Completion Date:09/01/2008

OMB Category:Other

Record ID: 56159

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Project Information:

Progress :- A site was identified at the Lawrence Berkeley National Laboratory (LBNL) where an existing non-metallic 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 Tetrachloroethyene (PCE) leakage. Controlled PCE spill experiments using cross-borehole seismic and complex resistivity methods were conducted in smaller cylinders and intermediate size tanks (100cm by 50cm by 40cm) 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 were 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 ten different geophysical methods: borehole and cross-borehole complex resistivity (CR), cross-borehole seismic tomography (ST), surface high frequence 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 downhole video logging. Data from this spill is currently being analyzed. A method of extracting cores from the saturated formations has been developed and successfully tested in the intermediate size tank. Experiments are underway to test various PCE remediation methods in smaller cylinders and tanks, before they are applied to the larger fiberglass tank.

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 non-metallic (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.

An extensive literature review has identified and evaluated PCE remediation technologies which have the potential to be characterized and monitored geophysically. Potential remediation methods evaluated include: pump & treat, thermal, oxidation, surfactant flushing (SEAR), and biological treatment. The DNAPL remediation method which is chosen would ideally be effective in breaking down the PCE yet [mildly] reactive with the subsurface so as to not mask or overwhelm any potential geophysical method. It was found that of the most successful remediation strategies; surfactant enhanced aquifer remediation (SEAR) and enhanced biodegradation are the two most promising remediation methods for free phase, residual, and dissolved DNAPL, and which show potential to be monitored geophysically. Other methods are: 1) sometimes very aggressive and tend to overwhelm any geophysical response (thermal heating, steam flushing); 2) do not require geophysical sophistication in monitoring (e.g. oxidation, thermal methods); 3) not very successful to warrant typically accepted practices (e.g. pump & treat) in the field; or 4) have already been successful

Relevance :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 nonaqueous-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 non-invasive geophysical techniques will allow for the rapid identification of the location of spilled LNAPLs 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 OERR, 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. The geophysics 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 OERR, OSW, Regions, and other interested program offices. The current and proposed future studies support the OERR high priority research need entitled, "Ground Water DNAPL Site Characterization" as identified by OERR staff (Sharon Frey, April 2001, OERR Research Priorities for ORD) and in the contaminated sites multi-year plan. It is through these reviews and communication with the client offices that ESD-LV can ensure 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).



Clients :Ken Lovelace, OERR; Randy Breeden, Shahid Muhmud, OSWER; Steve Hoffmann, OSW; James Hamilton, OW; David Wiley, OSWER; Jan Young - OSW; Carl Daly - OSW; Regions.

Project IDs:

ID Code :4058

Project type :OMIS