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Frequently Asked Questions
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Q:
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What kind of equipment do you use to find water?
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A:
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- GF 3000 computer-receiver, 310x75x255mm, 6kg incorporating computer, input circuitry, trigger
- Windows XP ProTM and Groundflow EKSTM software
- Waterproof equipment case and padded carry-case.
- Power, antenna, and trigger cables, four copper-clad steel electrodes
- Hammer switch (trigger)
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Q:
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What is the technology behind the equipment?
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A:
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The GF 3000 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 300 feet) and the “buffalo gun” source for deeper work (up to 1000 feet). We can use both sources.
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Q:
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What are some of the uses for the GF 3000?
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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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Q:
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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 the borehole is often completely wasted. American Water Surveyors’ new GF 3000 technology defines both the permeability
and the depth of aquifers, making it possible for the first time to estimate the flow of a borehole drilled at a GF 3000
survey site. Such estimates can be obtained at an insignificant cost, when compared with the cost of a dry borehole.
Because signals are only produced by moveable water in saturated rocks GF 3000 equipment also shows where there is no aquifer
and hence no borehole 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 boreholes are properly completed with the aquifer
layer open to flow and undamaged by drilling, the EKS predictions and borehole 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 borehole will produce zero, 6, or 50 gallons per minute.
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Q:
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Where and how can the EKS System be used?
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A:
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Applications
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GROUNDWATER SUPPLY
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ENVIRONMENTAL
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GEOTECHNICS/MINING
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Map and profile
aquifer depth and thickness to plan drilling
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Investigate polluted sites non-invasively and drill fewer
boreholes
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Map problem zones in major excavations (mines, foundations,
canals)
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Map and profile
aquifer quality (permeability and porosity) to manage drilling programs
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Gather abundant EKS permeability data for hydrogeological
flow models
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Map standing water levels and
aquifer size to plan dewatering operations
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Predict borehole yield and correct position and size
of pumps and casing
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Map chemical and radioactive pollution plume extent and
rate of movement
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Map leakage beneath dam foundations, out of reservoirs
or into tunnels
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Manage aquifer
development by siting new boreholes optimally for yield and long-term recharge
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Gather data on
leachate containment and movement non-intrusively at landfill sites
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Locate site groundwater supply for mine developments
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Delineate saline and polluted
aquifers
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Develop sustainable farm irrigation and plan the development
of large-scale agricultural land
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Explore for alluvial gravels for mineral extraction or
quarrying of aggregates
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Where to use
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SEDIMENTARY DEPOSITS
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BEDDED ROCKS
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CRYSTALLINE ROCKS
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Marine, beach and river deposits
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Sandstones
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Tropical weathered basement
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Wind-blown sands
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Limestone with matrix permeability
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Layered volcanic rocks
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Clay, sands and gravels
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Bedding-confined fractured units
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Weathered basalt
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Where to avoid
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SEDIMENTARY DEPOSITS
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BEDDED ROCKS
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CRYSTALLINE ROCKS
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Boulder
beds
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Cavernous limestone - water-filled caverns are too large
and permeable to image using EKS
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Unweathered rocks - no permeability therefore no signal
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Very impermeable deposits - no permeability therefore
no signal
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Very impermeable rocks - no permeability therefore no
signal
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Rocks with few isolated fractures - negligible porosity
giving little or no signal
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