The principal objective of geophysical surveys for groundwater resource investigation is to develop an understanding of the local or regional geology and hydrogeologic properties, or to identify the local groundwater contaminant transport mechanism. A variety of surface geophysical methods can be used to search for fracture zones and geologic contacts that may be suitable targets for production or recovery well installation. Borehole methods can be extremely effective in identifying small fractures, aquitards and producing zones, and mapping changes in contaminant plumes vs. time. Borehole data are also valuable as an aid to interpreting the surface geophysical data. Typical surface and borehole methods used by FPM Geophysical & UXO Services to conduct Groundwater Resource investigations include:
Electrical resistivity
Seismic reflection and refraction
Potential field [magnetics, gravity, spontaneous potential (SP)]
Time- and frequency-domain electromagnetics (EM) and very low frequency (VLF) EM
Borehole methods (caliper, EM induction, natural gamma, acoustic or optical
televiewer, heat-pulse and EM flowmeter, resistivity, and temperature to name a
few)
Key Benefits
Determine contaminant migration pathways
Provide reconnaissance for large areas to aid in resource estimation
Reduce drilling requirements and costs by “spotting” the most appropriate locations for wells and soil borings
Provide information on the subsurface that is not economically obtainable by
other means
Typical Objectives
Identify geologic contacts
Map saltwater intrusion boundaries
Map stratigraphy, paleochannels, and buried aquifers
Determine potential contaminant pathways or barriers
Locate and map fault, fracture zones, and permeable in bedrock
Map leaks from containment ponds, dams, reservoirs, and landfill liners
Delineate groundwater contaminant plumes and monitor movement with time
Identify depth to groundwater and map lateral changes in groundwater surface
Determine depths of aquitards and producing zones to properly locate screened
intervals during well construction and to optimize sampling efforts
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