Bryce Canyon

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Geologic Consultants

Email us at geologist@geomodel.com / 703-777-9788


Company Background

GeoModel, Inc. was founded in 1991 as a firm specializing in geologic consulting, geophysical surveying, and environmental consulting. The company principals have over 50 years of combined experience as geologic consultants and have conducted numerous geologic projects worldwide. All geologic consultants at GeoModel, Inc. are registered professional geologists.


Areas of Geologic Consulting

geologic mapping of rock units and soil layers
bedrock profiles
buried channels
geomorphology
flood plain analysis
fracture trace and lineament analysis
caves and karst
geologic fault studies
mining and minerals
geologic hazards


 

GPR profile showing sloping bedrock

The image above shows sloping bedrock in the subsurface. This image was obtained using ground penetrating radar (GPR).


Methods for Geologic Investigation

GeoModel, Inc. uses various methods for investigation of the geologic conditions in an area. Visual observation, professional knowledge, and aerial photograph analysis are some of these methods. GeoModel, Inc. also uses various geophysical methods to assist in the investigation of geologic conditions at a site or property. The sections below discuss some of the methods that GeoModel, Inc. uses.


Ground Penetrating Radar (GPR)

Ground penetrating radar (GPR) produces an underground cross-sectional image of the subsurface soil and rock. Depths up to 30 feet (10 meters) or more can be examined. GeoModel, Inc. conducts surveys using a GPR digital control unit and antennas with frequencies ranging from 200 to 400 MHz.

At geological mapping sites, GPR can locate buried stream channels, obtain bedrock profiles, and provide cross-sectional images of soil layers.

Vehicle-towed surveyHand-towed survey

Vehicle-towed GPR survey and Hand-towed GPR survey

 

The following are examples of GPR images of geologic features:

Sinkhole


Electromagnetic Conductivity (EM)

Electromagnetic conductivity measures the conductivity of the subsurface. This measurement includes the conductivity of soil, groundwater, and rock. GeoModel, Inc. has conducted numerous electromagnetic conductivity (EM) surveys worldwide.

Electromagnetic conductivity surveys are rapid and very accurate. The EM instruments are easily carried and can easily determine variations in ground conductivity that can indicate changes from materials of low conductivity (sand or granite for example) and materials of high conductivity (clay or shale deposits).

GeoModel, Inc.'s geophysicists can perform an EM survey anywhere in the world and with short notice. Survey costs are reasonable.

EM meter and operatorGeophysicist with EM meter

The EM conductivity meter can investigate the subsurface to a depth of about 20 feet.

 

Deeper EM surveyDeep EM meter in operation

The deeper EM can measure the terrain conductivity of the soil, rock, and ground water from the surface to about 100 feet deep.

 

EM survey resultsEM survey results

The conductivity contour map of the sinkhole above shows readings that range from low (blue color, outside the sinkhole area) to high (red and pink color, inside the sinkhole area).


Surface Resistivity

Surface resistivity is another method used for investigating the geology of the area. The electrical resistivity of the subsurface materials, which include soil and groundwater characteristics, is measured from survey stations at the ground surface.

MiniRes in operationMiniRes resistivity spread

 

Surface resistivity can be used to study lateral and vertical changes in the natural hydrogeologic setting. Surface resistivity can also be used to study contamination of soil and groundwater and to locate buried objects.

The apparent resistivity of the subsurface materials can be calculated by knowing the electrode spacing, geometry of the electrode positions, applied current, and measured voltage. The apparent resistivity values are entered into a computer program that calculates the geoelectric sections or columns for each sounding location, as shown in the images below. Surface resistivity measurements are reported in units of ohm-meters or ohm-feet.

Resistivity geoelectric section to 100 feet deepResistivity geoelectric section for clayey soils

Resistivity geoelectric section of spring in weathered bedrock

 

The depth of the resistivity measurement is related to the spacings of the electrodes and may vary depending on the subsurface conditions. The surface resistivity unit has a self-contained transmitter, capable of obtaining data to about 50 to 100 meters (160 to 300 feet), using self-contained, rechargeable batteries.


 

For a ground penetrating radar survey, click on your state below:

Map of the Untied States of America for ground penetrating radar projects

Alaska Hawaii Hawaii Washington Oregon California Nevada Idaho Arizona Utah New Mexico Colorado Wyoming Montana Texas Oklahoma Kansas Nebraska South Dakota North Dakota Louisiana Arkansas Missouri Iowa Minnesota Mississippi Illinois Wisconsin Michigan Alabama Tennessee Kentucky Indiana Ohio West Virginia Florida Georgia South Carolina North Carolina Virginia Maryland Maryland Delaware New Jersey New Jersey Pennsylvania New York Connecticut Connecticut Rhode Island Massachusetts Massachusetts Vermont Vermont New Hampshire New Hampshire Maine Washington, DC

 

e-mail: E-mail for geologist with ground penetrating radargeologist@geomodel.com

 


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