Objective:
Complex hydrogeologic conditions such as fractured and karst bedrock settings pose substantial economic and technical challenges to the characterization and remediation of dense nonaqueous phase liquid (DNAPL) source zones. The Army Environmental Center lists 34 installations where restoration may be technically impractical. Of the 34 installations, 26 are underlain by complex fractured rock or karst aquifers. The objective of this project is to demonstrate and validate the fractured rock passive flux meter (FRPFM) as new technology that measures the magnitudes and directions of cumulative water and contaminant fluxes in fractured rock aquifers. The specific project objectives are to 1) Demonstrate and validate an innovative technology for the direct in situ measurement of cumulative water and contaminant fluxes in fractured media; 2) Formulate and demonstrate methodologies for interpreting contaminant discharge from pointwise measurements of cumulative contaminant flux in fractured rock; and 3) Enable the technology to receive regulatory and end user acceptance. Technology Description: The technology to be demonstrated and validated is a new closed-hole passive flux sensor for fractured rock aquifers that directly measures: (1) the location of active or flowing fractures; (2) active fracture orientation (i.e., strike, dip, and dip orientation); (3) active fracture apertures; (4) the direction of groundwater flow in each fracture plane; (5) cumulative magnitude of groundwater flux in each fracture plane; and (6) cumulative magnitude of contaminant flux in each fracture plane. The sensor is essentially an inflatable packer or flute that holds a reactive fabric against the wall of a borehole and any water-filled fractures intersected by a borehole. The reactive fabric is designed to intercept and retain target groundwater contaminants--trichloroethylene (TCE), dichloroethylene (DCE), and vinyl chloride (VC); in addition, the fabric releases nontoxic tracers, some of which visibly indicate active fracture location, aperture, orientation, and direction of fracture flow along a borehole, while others quantify cumulative groundwater discharge in these fractures. Demonstration and validation studies will be conducted at two sites in Canada, where available field facilities will permit FRPFM testing in well-characterized rock wells and under controlled flows, and at two sites located at Department of Defense (DoD) installations where the underlying fractured rock aquifer is contaminated with chlorinated solvents. Direct FRPFM measures of active fracture location, aperture, orientation, direction, and magnitude of water and contaminant flux will be compared to results generated using competing technologies (e.g., borehole imaging tools, heat-pulse flow meter (Model 40 GEOFLO), temperature logging, and borehole dilution). The project will demonstrate the FRPFM is particularly cost effective for fractured rock characterization and monitoring when used in concert with other borehole technologies (e.g., high resolution temperature logging); and it is as cost effective as the current passive fluxmeter design for screened wells with additional capability for deep well deployments. Expected Benefits: Quantification of contaminant discharge near source zones is critical for assessing long-term risk, evaluating remedial performance, and meeting regulatory compliance. Current state-of-the-art technologies rely on numerous concentration samples in space and time to estimate contaminant discharges from a source zone but provide no direct measures of flow or contaminant mass flux. The FRPFM is designed to measure water and contaminant flux directly in fractured rock. It will bring the DoD much closer to estimating contaminant mass discharge from source zones and in turn expedite assessments of environmental risks and benefits associated with natural attenuation, source removal, or remediation at complex sites. For fractured bedrock sites, significant cost savings to DoD can be realized if sites are quantitatively shown to pose little off-site risk due to natural attenuation. Additional cost savings could be achieved through reduced costs for site assessment and long-term monitoring in deep wells. Used in concert with other technologies (e.g., high resolution temperature logging), the FRPFM may be able to reduce the overall costs of characterization. (Anticipated Project Completion - 2011) Principal Investigator: Dr. Kirk Hatfield University of Florida Department of Civil/Coastal Engineering P.O. Box 116580 365 Weil Hall Gainesville, FL 32611 Telephone: (352) 392-9537 Ext. 1441 Fax: (352) 392-3394 E-mail: khatf@ce.ufl.edu DoD Liaison: Ms. Erica Becvar HQ AFCEE/TDE Technology Transfer 3300 Sidney Brooks Brooks City Base, TX 78235-5112 Telephone: (210) 536-4314 Fax: (210) 536-5989 E-mail: erica.becvar@brooks.af.mil
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