In-Situ Permeable Flow Sensor
The In-Situ Permeable Flow Sensor uses a heat source to measure groundwater flow velocity. The instrument consists of a cylindrical heater with 30 calibrated temperature sensors on its surface. The Sensor is placed in the zone to be measured. The heater is turned on until the sediments and groundwater surrounding the probe are warmed by 20 to 30 degrees Celsius. In the absence of any flow past the probe, the temperature distribution on the surface of the instrument will be symmetrical. When there is flow past the probe, the moving water changes the heat distribution on the surface, thereby causing it to become asymmetrical. Thus, water flow rate can be extrapolated.
The key to accurately measuring groundwater flow velocity with this technology is to bury the tool in the ground in direct contact with the formation. This avoids all the negative effects that may result from the presence of a borehole, casing, screen and gravel pack. Direct burial is accomplished by drilling a hole to the desired depth, installing the probe though the casing, and retracting the casing. Saturated, unconsolidated sediments collapse around the tool, leaving it permanently in the ground.
Limitations and Concerns
The technology is appropriate only in saturated, unconsolidated (i.e., material that is relatively permeable) sediments.
The installation depth is limited only by the ability of drilling techniques to access the desired depth.
This technology measures groundwater flow in unconsolidated, saturated, sandy sediments. It enables the long-term monitoring of groundwater flow. The technology is not contaminant-specific. It can also be used to characterize the subsurface and determine if technologies such as Groundwater Circulation Wells and In-Well Air Stripping are appropriate.
Technology Development Status
This technology has been successfully tested at multiple field sites. It is commercially available.
Other Resources and Demonstrations
The In-Situ Permeable Flow Sensor has been tested at a variety of sites, including the Savannah River Site in South Carolina; the Strategic Petroleum Reserve Facility in Louisiana; and Edwards Air Force Base in California.
ÒIn-Situ Permeable Flow Sensor, Innovative Technology Report,Ó US Department of Energy. (18 p./215 KB; not available on line)
See http://www.osti.gov/bridge/servlets/purl/10181998-zywPC7/native/ for description of the test at the Savannah River Site.