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Frequently Asked Questions
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What kind of equipment do you use to find water?
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A:
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- GF 3500 computer-receiver
- Windows XP ProTM and Groundflow EKSTM software
- Power, antenna, and trigger cables, four copper-clad steel electrodes
- Hammer switch (trigger)
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What is the technology behind the equipment?
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A:
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The GF 3500 embodies the most significant advance in earth observation for many years in a simple robust package. The signals detected arise directly from the movement of water, not from the rock matrix. Our equipment and a seismic source are used to estimate the depth and quality of aquifers. The seismic source is used to create a sharp sound pulse. When the sound pulse moves through porous and permeable aquifers it travels fast in the rock matrix and slower in the water-filled pore space. Ions in the water are dragged away from their partners bound to the rock and an electrical dipole is set up that “flickers” at seismic frequencies. Where there are changes in the rock, as at bedding planes, the electromagnetic disturbance is caused to propagate to the surface at the speed of light. When these signals are detected they give unambiguous depth and thickness data, as with reflection seismic. The form of each signal gives information about the depth, thickness and permeability of the aquifer and this is used to estimate the likely water yield from a borehole drilled at the survey site. The signals detected arise directly from the movement of water, not from the rock matrix. The technique is quick, inexpensive and non-intrusive unlike its only real competitor, drilling. High resolution profiles of moveable water in aquifers can be produced for the first time. The equipment collects the electrical signals generated by the passage of seismic waves traveling through water-saturated rocks. A variety of seismic sources may be used. We recommend the use of a special hammer for shallow surveys (less than 350 feet) and the “buffalo gun” source for deeper work (up to 1500 feet). We can use both sources.
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What are some of the uses for the GF 3500?
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A:
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American Water Surveyors is dedicated to being the leading provider of electroseismic geophysical and logging equipment. This is used to map water table, groundwater (ground-water productivity) and aquifer permeability. Applications include borehole siting, completion planning, environmental monitoring, site investigation of saline intrusions, landfill contamination. The transmissivity of water can be mapped from the surface, and borehole yield (flow) estimated.
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Q:
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What are some of the benefits for using your service?
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A:
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- SEEING BENEATH THE GROUND
- LOW COST NON-INTRUSIVE AQUIFER QUALITY MAPPING
Mapping aquifer quality with an array of survey locations ensures that drilling costs are not wasted. Such maps can form the basis for water abstraction policy, aggregate extraction, or landfill planning at a small fraction of the cost of drilling. Many other applications are developing as the number of users grows. Drilling costs can be reduced by specifying where and how deep to drill. Dry-land farm acreage can be upgraded and improved. Mine investments can be secured with a reliable water supply. Landfill sites can be investigated non-intrusively. Polluted land can be upgraded by defining pollutant movement non-intrusively.
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Can you determine what kind of water flow I could expect before I drill for water?
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A:
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Until now there has been no way to tell before drilling how much water can be produced at any particular place. There is always some water underground but it is often impossible to get it to flow to the surface in useful amounts. The investment in a well is often completely wasted. American Water Surveyors’ new GF 3500 technology defines both the permeability and the depth of aquifers, making it possible for the first time to estimate the flow of a well drilled at a GF 3500 survey site. Such estimates can be obtained at an insignificant cost, when compared with the cost of a dry well. Because signals are only produced by moveable water in saturated rocks, GF 3500 equipment also shows where there is no aquifer and hence no well should be drilled.
EKS equipment cannot predict yield exactly because so much depends upon the local variations in the rocks, and also in the method of drilling and lining the borehole. Nevertheless, provided that the wells are properly completed with the aquifer layer open to flow and undamaged by drilling, the EKS predictions and well results should be similar. In most cases the flow rates are similar and the EKS predictions can be used with confidence to select borehole drilling locations. It is straightforward to tell whether a well will produce zero, 6, or 50 gallons per minute.
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