Purpose:

The Department of Defense (DoD) has a critical need for technologies that provide cost-effective long-term monitoring of volatile organic chemicals, petroleum and related compounds, trace metals, and explosives. Active remediation systems such as "pump and treat" and passive remediation systems such as natural attenuation as well as Resource Conservation and Recovery Act (RCRA) closure sites often require elaborate and expensive monitoring. This project will demonstrate and validate a 'flux meter,' which is a new technology for direct in situ measurement of both cumulative subsurface water and contaminant fluxes.

Description:

The 'flux meter' is a self-contained permeable unit that is inserted into a well or boring such that it intercepts groundwater flow but does not retain it. The interior composition of the meter is a matrix of hydrophobic and hydrophilic permeable sorbents that retain dissolved organic and inorganic contaminants present in fluid intercepted by the unit. The sorbent matrix is also impregnated with known amounts of one or more fluid soluble 'resident tracers'. These tracers are leached from the sorbent at rates proportional to the fluid flux. Following exposure to groundwater flow for a period ranging from days to months, the meter is removed and the sorbent carefully extracted to quantify the mass of all contaminants intercepted and the residual masses of all resident tracers. The contaminants' masses are used to calculate time-averaged contaminant mass fluxes, while residual resident tracers masses are used to calculate cumulative fluid flux.

As a tool for long-term monitoring, a fencerow of flux meters installed immediately downgradient from a groundwater contaminant source can be used to characterize source strength. The spatial distribution of measured fluxes, when integrated over the fencerow, produce estimates of contaminant mass loadings to groundwater. Because water and contaminant flux measurements reflect cumulative values, reliable time-averaged fluxes can be calculated; thus, it is possible to calculate reliable monthly and annual contaminant mass loadings to an aquifer. The flux meter will be validated through demonstrations at three DoD contamination sites.

Benefits:

The flux-meter is designed to quantify cumulative contaminant fluxes leaving a known source zone or a hazardous waste site. By monitoring cumulative flux rather than contaminant concentrations, the risk posed by a site can be better evaluated and decisions regarding remedial efforts can be made based on reducing risk. Cost savings to DoD will be realized by: 1) quantitatively demonstrating that active remedial action is not required because mass flux is low and/or it can be attenuated by natural processes; 2) limiting spatial monitoring at compliance boundaries; and 3) decreasing the temporal frequency of sampling. (Anticipated Project Completion - 2005)

Contacts:

Technical Contact:
Dr. Kirk Hatfield
University of Florida
Department of Civil and Coastal Engineering
P.O. Box 116580
Gainesville, FL 32611
Telephone: (352) 392-0956
Fax: (352) 392-3394
E-mail: khatf@ce.ufl.edu

DoD Liaison Officer:
Ms. Erica Becvar
AFCEE/ERT
3207 Sidney Brooks
Brooks AFB, TX 78235
Telephone: (210) 536-4314
Fax: (210) 536-4330
E-mail: erica.becvar@brooks.af.mil