USEPA Evaluation

TECHNOLOGY EVALUATION REPORT:
HYDROTECHNICS IN SITU FLOW SENSOR
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Abstract:

The U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE) Program evaluated performance of HydroTechnics, Inc. flow sensors in measuring the three-dimensional flow pattern created by operation of the Wasatch Environmental, Inc. (WEI) groundwater circulation well (GCW). The GCW is a dual-screened, in-well air-stripping system designed to remove volatile organic compounds (VOC) from groundwater. Operation of the GCW creates a groundwater flow pattern that forms a three-dimensional regime known as a “circulation cell.” EPA's evaluation of the GCW circulation cell involved use of in situ groundwater velocity flow sensors that were developed at Sandia National Laboratories and manufactured by HydroTechnics, Inc.

This Technology Evaluation Report (TER) documents and summarizes the findings of EPA's evaluation of HydroTechnics' flow sensors. The flow sensors are in situ instruments that use a thermal perturbation technique to directly measure the velocity of groundwater flow in unconsolidated, saturated, porous media. The manufacturer claims that the flow meter can measure horizontal and vertical flow rates and direction in the range is 0.01 to 2.0 feet per day (ft/day) (0.3 to 60.96 centimeter per second [cm/s]). The GCW is a patented system manufactured by WEI and was demonstrated at Cape Canaveral Air Station (CCAS) by the U.S. Air Force Center for Environmental Excellence (AFCEE). AFCEE conducted a comprehensive evaluation of the GCW, including contaminant mass removal rates, groundwater dye tracer studies, and numerical modeling. Demonstration data collected by AFCEE are documented separately in “Groundwater Circulation Well Technology Evaluation at Facility 1381, Cape Canaveral Air Station, Florida Technology Summary Report” (Parsons 2001).

The primary conclusions of EPA's evaluation of the HydroTechnics flow sensors include:

During GCW operation, the groundwater velocities measured by all seven sensors increased by more than 0.1 ft/day, indicating that (1) the sensors were within the circulation cell established by the GCW, and (2) the horizontal extent of groundwater circulation was greater than 15 feet. Flow direction data further support the establishment of a circulation cell and that all the flow sensors are within the horizontal extent of groundwater circulation cell.
The demonstration data suggest that the flow sensors are responsive to changes in groundwater flow conditions and can be used to help define and evaluate the three-dimensional flow patterns.

SENSOR TECHNOLOGIES USED DURING SITE REMEDIATION ACTIVITIES:
SELECTED EXPERIENCES
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Purpose of Report

Environmental remediation includes many activities that require measurement and monitoring of parameters such as contaminant concentrations, media characteristics, and systemic parameters. In recent years, there has been an increase in the number and types of sensor technologies used during site remediation. These include technologies that are used for performing real-time and continuous measurements, remote monitoring, remote operation, and system automation. The U.S. Environmental Protection Agency (EPA) prepared this report to provide an overview of several types of sensor technologies and a summary of selected experiences with using the technologies during site remediation activities. The report highlights the applications, implementation, strengths and limitations, and lessons learned from actual projects that have
used one or more sensor technologies as part of an overall site remediation strategy. Appendices one through seven provide case studies for specific sites that have used sensor technologies during site remediation activities.

This report does not provide guidance on the selection of a specific type or vendor of sensor technology; these technologies are most cost-effective under specific environmental, chemical, and physical conditions. Numerous site-specific considerations, such as site geology, soil, and aquifer characteristics, chemical, physical, and biological parameters of affected media, and chemicals of concern, among many others, can impact the overall cost-effectiveness of a system.In preparing this report, EPA collected available information on sensor technologies for remedial projects performed at Superfund sites, federal/military sites, and other sites. EPA attempted to compile information that was readily available and current for each project as of Summer/Fall 2004, however, in some cases, EPA was not able to confirm the available information. Some case studies include information provided primarily by the technology vendor, with limited input from a regulatory authority. In addition, for many of the projects, there were gaps in the types of information available (e.g., for some sites, performance data were not available, or there was a limited amount of data that independently evaluated sensor performance). This report is not a comprehensive review of all available sensor technologies or vendors.