Information Last Revised: 2/23/93
TTP Reference Number: AL-2011-01
1. Technical Name of Technology: In Situ Permeable Flow Sensor
2. Common Name of Technology: Flow Sensor
3. PI and Telephone No: Sandy Ballard, (505) 844-6293
4. Affiliation: Sandia National Laboratory
5. Technology Category: Charaterization and Monitoring
6. Developers: Sandy Ballard
7. Application
7.1. Where (in-situ/ex-situ): In situ
7.2. Media: Saturated, permeable, unconsolidated materials.
7.3. Targeted Contaminants: Not applicable
8. Scope of project (feasibility study, treatability, bench, pilot, field):
Development and field demonstration
9. Integrated Demonstration (ID) Need/Requirements:
Since groundwater flow is perhaps the most important mechanism for the dispersal of many types of toxic waste once they have been released into the subsurface, accurate information about the groundwater flow field is critical to the characterization of waste sites, monitoring of waste remediation activities and monitoring the post-closure performance of remediated waste sites.
10. Objective
10.1. Objective of technology (i.e., This technology will destroy VOCs in groundwater.):
The technology can measure the full three dimensional groundwater flow velocity vector at a point in a saturated, permeable, unconsolidated material.
10.2. Baseline (baseline technology to which it is compared):
Hydraulic Head Gradients & Conductivities Tests (Hydraulic Tests)
11. Process Description:
The basic operating principle of this technology is to bury a thin cylindrical heater vertically in the ground at the point where the groundwater flow velocity is to be measured. If the heat flux out of the cylinder is uniform over the surface of the cylinder then the temperature distribution on the surface of the cylinder will vary as a function of the direction and magnitude of the groundwater flow velocity past the cylinder. In the absence of any flow past the device, the temperature on the surface of the probe will be independent of azimuth and symmetric about the vertical midpoint of the probe. The vertical midpoint will be warmer than the ends of the probe because heat transfer away from the ends of a finite length cylinder is more efficient than from the midsection of the cylinder. Groundwater flow past the device perturbs the surface temperature distribution with the pattern and magnitude of the temperature variations reflecting the direction and magnitude of the groundwater flow velocity. In essence, relatively warm temperatures will be observed on the downstream side and relatively cool temperatures on the upstream side of the instrument as the heat introduced into the formation by the heater is advected around the probe. If the groundwater flow has a vertical component, the vertical temperature distribution on the surface of the probe will no longer be symmetric about the vertical midpoint of the probe but rather will be skewed in the direction of the flow. The surface of the downstream end of the probe will be warmer than the upstream end. If there is a significant horizontal component to the flow velocity, the surface temperature distribution will not be independent of azimuth but rather the surface temperature will vary approximately as the cosine of the azimuth with the downstream side of the probe being warmer than the upstream side. The magnitude and direction of the three dimensional flow velocity vector are determined from the magnitude and the pattern of the temperature variations on the surface of the probe, respectively. The sensors should be sensitive to groundwater flows as low as a few meters/year.
11.1. Input:
Place instrument in the ground where the velocity is to be measured.
11.2. Output:
A description of the magnitude and direction of the groundwater flow velocity vector.
12. Summary of Technology Advantages (relative to the baseline: faster, better, cheaper, safer):
This technology can measure the full 3 dimensional flow velocity vector at a point in a permeable medium using only one hole. Four holes are required for a similar measurement using the standard technique. Information about the hydraulic conductivity of the medium is required in the standard technique. This is generally determined using a pump test in which large quantities of water are pumped from the well. At contaminated sites, disposal of this purge water can be difficult and expensive. With In Situ Permeable Flow Sensors, no information about the hydraulic conductivity is required. The flow sensors measure the velocity characteristic of a very small volume of material, on the order of 1 cubic meter. The standard technique measures a velocity which is an average of the velocity over a much broader region, one whose dimensions are characterized by the separation of the boreholes. It is easy to set up a flow sensor and monitor it remotely for extended periods of time.
13. Limitations of Technology (relative to the baseline: faster, better, cheaper, safer):
Measures the velocity at essentially a point. Sometimes the average velocity over a wider area is desirable.
14. Major Technical Challenges:
The resolution of the technology is determined by how accurately the temperature distribution on the surface of the instrument can be measured. Currently, temperature differences of about 0.01°C can be measured. At this level, flow velocities as low as a few meters/year can be resolved. Probe design needs to be improved to assure long term reliability of electronics and sensors in groundwater conditions.
15. Technical Effectiveness:
15.1. Performance
15.1.1. Remaining Contamination: (contamination mobility reduction, volume reduction, toxicity reduction)
Summary (20 words or less): Not applicable
Further Description (unlimited length):
15.1.2. Process Waste
15.1.2.1. Status of waste (mobility, volume, hazard, recyclability)
Summary (20 words or less): The technology produces no waste.
Further Description (unlimited length):
15.1.2.2. Treatment (needed, available)
Summary (20 words or less): Not applicable
Further Description (unlimited length):
15.1.2.3. Decontamination / Decommissioning
Summary (20 words or less): Not applicable
Further Description (unlimited length):
15.1.2.4. Disposal (needed, available)
Summary (20 words or less): The probes are permanently buried in the ground. There is nothing to dispose of.
Further Description (unlimited length):
15.1.3. Practicality
15.1.3.1. Foreclose Future Options
Summary (20 words or less): Use of this technology at a site does not preclude using any other technology at the same time or at some future date.
Further Description (unlimited length):
15.1.3.2. Reliability
Summary (20 words or less): Current prototype sensors last for approximately 1 year.
Further Description (unlimited length): Failure occurs when the water proof coatings ultimately leak allowing water into the probe where it shorts out the electronics. Improvements in this area are expected.
15.1.3.3. Failure Control
Summary (20 words or less): Failure does not present any serious consequences other than the fact that useful flow velocity measurements will no longer be available from the probes.
Further Description (unlimited length):
15.1.3.4. Ease of Use
Summary (20 words or less): The probes are simple to install and monitor. Data from a number of probes at the same site can be collected an sent via modem to computers at a remote site.
Further Description (unlimited length): Other than for installation and occasional maintenance, the system can be operated remotely for extended periods of time.
15.1.3.5. Infrastructure
Summary (20 words or less): Electric power, either from line power or generator, is required. For remote monitoring, access to a telephone line or cellular phone service is also desirable.
Further Description (unlimited length): Data transfer by RF transmission is presumably possible.
15.1.3.6. Versatility
Summary (20 words or less): Not applicable
Further Description (unlimited length):
15.1.3.7. System Compatibility
Summary (20 words or less): Not applicable
Further Description (unlimited length):
15.1.3.8. Off-the-Shelf (procurement ease)
Summary (20 words or less): Virtually all of the components for the sensors and the data acquisition system are available commercially.
Further Description (unlimited length):
15.1.3.9. Maintainability
Summary (20 words or less): The system is easily maintained. Systems have been reliably operated remotely for in excess of one year.
Further Description (unlimited length):
15.1.3.10. Safety Measures
Summary (20 words or less): The probes are very safe. The only hazard is electric power.
Further Description (unlimited length):
15.1.4. ``Works'' (functions as intended):
Summary (20 words or less): The sensors work as intended. Field tests indicate that flow velocities as low as a few meters/year are resolvable.
Further Description (unlimited length):
15.2. Cost
15.2.1. Start-Up Cost
Summary (20 words or less): Purchase of a calibration facility, data acquisition system and computer for data analysis is estimated at approximately $25K
Further Description (unlimited length):
15.2.2. Operations and Maintenance Cost
Summary (20 words or less): Each sensor is estimated to cost between $500 and $700. In remote applications, approximately one tenth of a person's time is required to collect and analyze the data.
Further Description (unlimited length):
15.2.3. Life-cycle cost
Summary (20 words or less): Unknown.
Further Description (unlimited length):
15.3. Time
15.3.1. Years Until Available
Summary (20 words or less): It is expected that this technology will be commercially available by the end of 1993.
Further Description (unlimited length):
15.3.2. Speed/Rate
Summary (20 words or less): Once the heater on the probe is activated, a flow velocity measurement can be obtained after about 24 to 48 hours.
Further Description (unlimited length): The heater can be left on for extended period (weeks, months) for continuous monitoring of the flow velocity. The technology can measure groundwater flow velocities as low as a few meters per year.
15.3.3. Years to Finish
Summary (20 words or less): Flow sensors can monitor groundwater flow for as long as required, up until the time they leak (currently approximately one year).
Further Description (unlimited length):
16. Environmental Safety and Health
16.1. Worker Safety
16.1.1. Exposure to Hazardous Materials/Hazards
Summary (20 words or less): None.
Further Description (unlimited length):
16.1.2. Physical Requirements
Summary (20 words or less): None.
Further Description (unlimited length):
16.1.3. Number of People Required
Summary (20 words or less): One.
Further Description (unlimited length):
16.2. Public Health and Safety
16.2.1. Accidents
Summary (20 words or less): It is very difficult to envision how a member of the public could be harmed by this technology.
Further Description (unlimited length): Electric shock is the only foreseeable possibility but is adequate precautions are taken, the possibility is exceedingly remote.
16.2.2. Routine Releases
Summary (20 words or less): None.
Further Description (unlimited length):
16.2.3. Transportation
Summary (20 words or less): There is no hazard associated with transporting the sensors.
Further Description (unlimited length):
16.3. Environmental Impacts
16.3.1. Ecological Impacts
Summary (20 words or less): None.
Further Description (unlimited length):
16.3.2. Aesthetics
Summary (20 words or less): None.
Further Description (unlimited length):
16.3.3. Natural Resources
Summary (20 words or less): None.
Further Description (unlimited length):
16.3.4. Energy Demands
Summary (20 words or less): Approximately 120 Watts of DC electric power are required per flow sensor to run the on-board heaters.
Further Description (unlimited length): Small amounts of 110 VAC power are required to run the data acquisition system.
17. Socio-Political Interests
17.1. Public Perception
17.1.1. Proponent Reputation
Summary (20 words or less): Not applicable
Further Description (unlimited length):
17.1.2. Familiarity / Understandability
Summary (20 words or less): The public is currently not familiar with this technology.
Further Description (unlimited length): The problem to be solved and the basic operating principle of the technology are quite simple and readily understood by the interested layman.
17.2. Tribal Rights / Future Land Use
17.2.1. Capacity for Unrestricted Use (terrestrial, aquatic)
Summary (20 words or less): Not applicable
Further Description (unlimited length):
17.3. Socio-Economic Interests
17.3.1. Economic Impacts
Summary (20 words or less): None.
Further Description (unlimited length):
17.3.2. Labor Force Demands
Summary (20 words or less): None.
Further Description (unlimited length):
18. Regulatory Objectives
18.1. Compatibility with Cleanup Milestones
Summary (20 words or less): This technology can help to understand the dynamics of a waste remediation operation and thereby the effectiveness and efficiency of the cleanup effort.
Further Description (unlimited length):
18.2. Regulatory Infrastructure / Track Record
Summary (20 words or less): The author does not know to what extent regulators are familiar with this type of technology.
Further Description (unlimited length):
18.3. Regulatory Compliance
Summary (20 words or less): Not applicable
Further Description (unlimited length):
19. Industrial Partnerships
19.1. Company Names:
Many companies have expressed an interest in this technology. Discussions are underway with SIE, Inc., of Ft. Worth Texas. They plan to begin commercialization of the technology in 1993.
19.2. Rationale:
19.3. Contract Mechanism:
19.4. Other Potential Companies:
A similar technology for use in boreholes/wells is marketed by KV Analytical.
19.5. International:
20. Intellectual Property
20.1. Patent Ownership:
There is no patent on this technology, it is in the public domain. Sandia has applied for copyrights on our engineering drawings and on the software that interprets flow sensor data.
20.2. Other Owners:
20.3. Patent Number:
21. Cost Sharing:
The Office of Technology Development has been the sole funding agency for the development of this technology.
22. Background on this technology (Where did the idea come from? Who else is doing similar work? What have the results been to date? What is the most significant competitor to this technology?):
The first groundwater flow sensor based on this principle was developed at Sandia National Laboratories with funding from the U. S. Department of Energy's Office of Basic Energy Sciences. It was designed primarily for scientific studies in thermally active regions of the shallow crust of the Earth. In 1990, the deployment strategy of the technology was completely reevaluated to make it amenable to use in environmental characterization and monitoring. The sensors have been tested at the Savannah River Site in South Carolina at the site of the VOC in Non Arid Soils Integrated Demonstration. Most recently the technology has been tested at another site at Savannah River at a location where the groundwater flow velocity is very well characterized using standard hydrologic techniques. The results from this test indicate that the flow sensors produce reliable results both in terms of the direction and the magnitude of the flow velocity.
23. Reference Documents:
Ballard, S., ``In Situ Permeable Flow Sensors at the Savannah River Integrated Demonstration: Phase I Results'', SAND92-1952, Sandia National Laboratories, October, 1992.
Ballard, S., ``An In Situ Permeable Flow Sensor to Monitor Groundwater Flow'', Sensors Magazine, 9, p20-26, December, 1992
Ballard, S., ``Flow Sensors'', Sandia Technology: Engineering and Science Accomplishments, 1992.