Willowstick's technology is receiving mainstream recognition from industry leading publications. The following are the latest published material and announcements:
The Differences between the Willowstick Method and DC Resistivity
The Differences between the Willowstick Method and DC Resistivity
The Willowstick method is an imaging technology designed for mapping groundwater. It is quite different from DC Resistivity technologies such as Electrical Resistivity Tomography (ERT), High Resolution Resistivity, and Electrical Resistivity Imaging (ERI).
The DC resistivity method energizes the subsurface from various standpoints to measure the apparent resistivity of the bulk material. For brevity, the energizing dipoles and the measuring dipoles will be referred to as the source and receiver, respectively. Electrical current spreads out from the source into the subsurface volume beneath and between electrodes to complete the electrical circuit. The voltage or potential difference between electrodes at the earth’s surface is measured (receiver) to calculate the apparent resistivity for each source/receiver setup. The bulk subsurface resistivity or the ability of the subsurface to impede electric current flow (ohm-meters) is calculated by knowing the amount of electric current flowing through the ground and the voltage between the two potential electrodes. Resistivity is the inverse of conductivity, so low resistivity indicates high conductivity. Subsurface resistivity is a function of the porosity or the void space, the pore fluid conductivity, and the conductivity of the formation (rock or soil particles). For example, water as a pore fluid usually has dissolved ions that reduce the subsurface resistivity by promoting electrical current flow. The more dissolved ions in the groundwater, the lower the subsurface resistivity will be.
A resistivity survey is usually designed to map vertical or lateral changes in subsurface resistivity. In a vertical sounding, the pair of source electrodes are moved increasingly farther apart from a central receiver dipole to measure resistivity as a function of depth. Lateral profiling is typically accomplished with a dipole-dipole or similar array, where both the source and receiver dipoles have constant separation and are moved progressively along a survey line. Resistivity sounding and profiling can yield pseudo-sections of the subsurface, not true cross-sections due to the inaccuracy of the underlying assumption that the subsurface is homogeneous or horizontally layered. Surveying multiple parallel and/or perpendicular lines allows 3D information to be gathered. With 3D data, subsurface structures can be delineated better in both horizontal and vertical extent. The value of the DC resistivity method is its ability to delineate geologic structure boundaries that have contrasting resistivities to their surroundings. For example, High Resolution Resistivity may be used to map a cyanide solution as it spreads out from an injection well drilled into a leach pad. This plume can be mapped very accurately with DC resistivity because the cyanide solution is electrically conductive while the dry or semi-saturated parts of the leach pad will be much more resistive to electric current flow. The extent of low resistivity can be mapped very accurately with a tight electrode grid. Plotting and outlining the low resistivity anomaly can produce an accurate map of the cyanide solution plume as it spreads through the leach pad.
Willowstick is of the opinion that resistivity methods and its own method are complementary technologies and Willowstick actually utilizes its own DC resistivity technology called RaMPS. The RaMPS array is designed to gather horizontal (profiling) and depth (sounding) information via a proprietary electrode arrangement based on monopole galvanic resistivity measurements. The proprietary electrode array and plotting techniques applied with a RaMPS survey have been proven more accurate in side by side comparisons than traditional resistivity methods.
The Willowstick method, on the other hand, directly energizes the water of interest with an alternating current (AC). As with all electrical circuits, electric current will choose the paths of least resistance between strategically placed electrodes. Electric current flow is sustained through ionic conduction in the water. AquaTrack, by energizing a specific layer or water pathway, can trace the targeted water specifically from one place to another. If there is no specific water pathway the AquaTrack Technology will show that the area in question is uniform. AquaTrack is principally used to map concentrated groundwater flow paths where the start and end are known such as leaks in dams, weaknesses in barriers and water flow through high porosity zones (faults, fractures and karst features). These features represent the paths of least resistance to electric current flow between the strategically placed electrodes.
The Willowstick method’s principal measurement is the magnetic field, not the electric field (voltage). The magnetic field is generated by electrical current flowing through a conductive path (Ampere’s Law). The magnetic field is measured with three high inductance coils that are oriented along the x, y and z directions. The magnetic field measured has the same frequency as the injected electrical current, so the signal can be distinguished from other noise sources like spherics and the power grid (50 or 60 Hertz) and its harmonics. Measuring the magnetic field (pure magnetic field not electromagnetic field) has two advantages:
- The magnetic field is directly related to electric current flow; therefore, modeling electric current flow is a simple and direct application of established physical principles (Biot-Savart Law).
- Secondly, the magnetic field is not shielded by overlying conductive layers such as shale and clay. This allows the Willowstick instrument to receive signals from depth to map the targeted conductive path. It has been ground truthed to depths up to 1km.
Keep in mind that even the best of geophysical technologies when incorrectly applied will yield unsatisfactory results. The key to getting good results is selecting the appropriate technology based on what you are trying to find and then correctly applying that technology. Both DC resistivity and AquaTrack have their appropriate applications and are often used to complement each other in characterizing the subsurface.
In conclusion, resistivity’s strength is mapping geologic structures that have contrasting electrical properties. The Willowstick method excels in its unique ability to map the specific preferential flow paths of groundwater in a wide variety of applications, both shallow and deep.
The Leading Edge
Tuesday, 01 February 2011 00:00
Unique applications of MMR to track preferential groundwater flow paths in dams, mines, environmental sites and leach fields
The Leading Edge
Peer Reviewed ArticleDownload PDF 1.95 Mb
Divine Idea: Plugging Dams and Tracking Underground Water, Using an Earth MRI.
Sri Lanka's Samanalawewa dam on the country's Walawe River has been leaking since the day it was completed in 1992. In the interim, the country has spent more than $65 million to plug the leaks in its second-largest dam, built to power the 120-million-watt Samanalawewa Hydroelectric Project. A 2005 study found that the reservoir—located near the town of Balangoda about 100 miles (160 kilometers) southeast of the capital Colombo—was leaking continuously at a rate of 475 gallons (1,800 liters) per second. And shotgun-type methods to solve the Samanalawewa dam problem—including the use of 13,640 tons of cement to reinforce the dam and the dumping of 1.8 million cubic feet (50,000 cubic meters) of clay to plug the holes—have failed.
The problem is that geologists and engineers do not know where all of the leaks are. So they turned to U.K. engineering consultant firm Atkins Global. Atkins performed a preliminary inspection of the dam and surrounding area for three weeks in February using AquaTrack technology developed by Draper, Utah–based Willowstick Technologies. The roughly $3-million project calls for Atkins Global to do additional survey work using AquaTrack this summer to pinpoint the sources of the leakage and spend the subsequent wet season planning precisely where to inject grout to plug those holes, work that Andy Hughes, the company's director of dams and reservoirs, anticipates will begin early next year.
Here's how AquaTrack works: Two electrodes—each three feet (one meter) long—are lowered down, one into the reservoir and the other someplace on the opposite side of the dam (typically in a sinkhole or other standing water downstream of the dam). The top of each electrode is connected with a wire. Once they switch on the electricity, "We've basically created a large circuit," says Paul Rollins, Willowstick's vice president of business development. Because groundwater is a conductor, the electrical current follows it between the electrodes, creating a magnetic field that can be detected on the surface using a sensitive magnetic receiver.
View images of how AquaTrack works
Once the magnetic field is generated, Willowstick's scientists walk the ground between the probes in a gridlike pattern with an instrument that collects data about the frequencies it detects underground. (The researchers are most interested specifically in the 380 hertz signals that AquaTrack's electrodes emit). The instrument is contained in a box that is three feet (one meter) tall and six inches (15 centimeters) square and held upright by a tripod and can collect thousands of readings in just five minutes, according to Rollins. (The technology has already been used successfully at a number of dams, including River Reservoir Dam No. 3 on the Little Colorado River in Arizona and Wolf Creek Dam on the Cumberland River in southern Kentucky.)
The circuit emits a magnetic field at 380 hertz that follows any groundwater it finds, Rollins says, "because water's really the best conductive [material] under the ground." The greater the amount of saturation, the greater the magnetic field, which emanates upward where it is recorded by Willowstick's surface sensing instruments. The gathered information is uploaded to computers at Willowstick's facilities, where researchers follow the thread of any 380 hertz readings to map the flow of underground water sources.
This will help determine the source of the leak, even if the leak is under the dam, Hughes says. "All dams leak to some extent," he adds, "but we don't want them to get out of hand."
U.S. companies have used AquaTrack to map dam seepage as well as determine the extent and location of groundwater those companies may have contaminated. Once a company that owns a plant or mine, for example, discovers it has polluted the local groundwater (or has been ordered by the U.S. Environmental Protection Agency to investigate the possibility that it has), the only real way to understand the problem to this point has been to dig a series of wells—generally six inches in diameter—to sample soil and underground water for contaminants, Rollins says.
Companies generally pay up to $120,000 to drill each well, so "they're not going to want to put 100 holes in the ground," Rollins says. "By creating theoretical flows in a modeling environment, the scientists can create theoretical magnetic fields," he adds. "They will then model these flows until the theoretical fields match [the data] collected in the field. Once they get the shape of the theoretical anomaly to match the actual data, then they can accurately determine depth of the dam seepage or groundwater." The goal here, as when the technology is used to find dam leaks, is to inform engineers as precisely as possible where they should drill to either pour concrete (in the case of a leaky dam) or take water samples to find the route of the contaminated water.
AquaTrack is designed to function much the way an MRI or X-ray is used locate a health problems within the body prior to surgery. "You wouldn't walk into a doctor's office and tell them to cut you open to find out what's wrong," Rollins says. "You'd first want to get an X-ray or MRI."
Of course, AquaTrack is not the only technology that allows scientists and business prospectors to better understand what lies beneath. Oil and gas companies for years have used the techniques of blasting or pounding into the ground and measuring the resulting shock waves to determine a site's crustal composition and, more importantly, where they might want to drill. "The acoustic signal travels through the Earth, and at each rock layer interface some of the signal bounces back up to the surface to be recorded by the sensor array," says Alex Krueger, vice president of research, development and marketing for Headwave, Inc., a Houston-based maker of software that can make maps out of raw data. "Thus, an image of the subsurface layers can be created."
Froehling & Robertson shares ACEC-VA Grand Award with Willowstick Technologies.
SALT LAKE CITY --Willowstick Technologies has been credited with helping Froehling and Robertson, a Richmond, Virginia-based multi-disciplinary engineering firm win a Grand Award by the American Council of Engineering Companies of Virginia (ACEC-VA).
Froehling and Robertson (F&R) were honored for the work they performed on the Virginia Department of Game and Inland Fisheries' (VDGIF) Laurel Bed Dam in 2008. Willowstick’s AquaTrack subsurface water mapping technology helped the firm discover seepage and guide a grout program design to prevent leakage.
In 2007, the VDGIF identified seepage at the Laurel Bed Dam as a significant concern and called on F&R to perform a subsurface exploration and design a grouting and repair program. To help find the seepage paths in the curtain, F&R brought in Willowstick Technologies and AquaTrack.
Willowstick collected hundreds of magnetic field readings, which were created by energizing seepage paths with a signature electrical current. In just a matter of weeks, F&R had a full 3-D rendering of the subsurface water paths with minimal cost and disruption to the surrounding area. That information was used to benefit the rest of the project, and F&R was eventually able to save Virginia taxpayers more than $600,000 off the original estimate.
"It is a great honor to win a Grand Award," said F&R Regional Vice President Don Sipher shortly after the ceremony. "The ACEC-VA's recognition of our efforts validates F&R's approach to serving our clients. Willowstick and our other partners helped us continue our reputation of efficient and cost-effective solutions to our clients’ problems."
“We’re pleased that F&R recognized AquaTrack’s capabilities and invited us to be a part of the Laurel Dam project,” Paul Rollins, Willowstick’s Vice President of Business Development, said. “We think that our ability to deliver accurate, reliable intelligence of seepage flow paths combined with unparalleled value can help our clients win many awards such as this one in the future.”
Willowstick was named in February as the top green business in the state of Utah by Utah Business Magazine and the iQ Awards. To see how AquaTrack works and to learn more about Willowstick, please log on http://www.willowstick.com.
Willowstick is a leading provider of innovative subsurface water mapping services. Its proprietary, proven technologies, AquaTrackTM and RaMPSTM, give clients an enhanced understanding of subsurface water characteristics. This increased knowledge and insight allow industry leaders to more efficiently and cost-effectively plan remediation and monitoring strategies for their hydrogeologic needs, saving them time and money. For more information, please visit http://www.willowstick.com or call 801.984.9850.
Copyright Business Wire 2009
Willowstick Technologies Wins iQ Award for Green Business.
SALT LAKE CITY -- Willowstick Technologies, the leading provider of innovative subsurface water mapping services, was recognized Wednesday as one of the top earth-friendly businesses in the state, winning an award in the category of Green Business at Utah Business magazine's iQ Awards.
In a ceremony at Salt Lake City's Wells Fargo Bank Building, Willowstick was recognized for providing alternatives to traditional methods of groundwater detection. Willowstick's AquaTrack[TM] detection method creates contoured, 3-D renderings of subsurface water with minimal disruption to the surrounding environment. The resulting information can be used by businesses and communities to identify subsurface water pathways for possible public use, groundwater cleanup, exploration or many other purposes.
"Utah Business magazine's iQ Awards program honors companies that have demonstrated progressive thinking, hard work and innovation. Willowstick, iQ award recipient in the Green Business category, has proven to be a company that exemplifies those traits," said Utah Business magazine Managing Editor Sarah Ryther-Francom. "The company's innovative AquaTrack technology deserves such recognition, as it is helping to safely and 'greenly' map water systems throughout the world. Utah Business was pleased to honor Willowstick for this technology and the company's overall innovative processes."
"We're pleased to be recognized by Utah Business and Wasatch Digital IQ for our efforts because we believe our technology can help companies to be good stewards of our environment," said Paul Rollins, Willowstick's vice president of business development. "We take pride in the fact that our technology can help to protect our precious groundwater resources and our clients appreciate the fact that they can save money by reducing drilling and eliminating guesswork." The iQ (innovation quotient) Awards are awarded in 10 categories, each containing three finalists culled from dozens of nominees.
The purpose of the awards, presented by Utah Business and Utah Digital IQ magazines, is to recognize Utah companies driving the latest in technology innovation.AquaTrack is a patented non-intrusive geophysical technique capable of mapping groundwater at depths exceeding 3,500 feet (1 kilometer) over large areas. The mapped water body is energized, and the electrical current flows preferentially through saturated subsurface materials, creating an induced magnetic field that is measured at multiple points on the ground surface, typically in a grid pattern. This data is then turned into multiple renderings that display valuable characteristics about the location of groundwater preferential flow paths.
To see how AquaTrack works and to learn more about Willowstick, please log on
Willowstick is a leading provider of innovative subsurface water mapping services. Its proprietary, proven technologies, AquaTrack[TM] and RaMPS[TM], give clients an enhanced understanding of subsurface water characteristics. This increased knowledge and insight allow industry leaders to more efficiently and cost-effectively plan remediation and monitoring strategies for their hydrogeologic needs, saving them time and money.
For more information, please visit www.willowstick.com or call 801.984.9850.
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