Question 1

Ground Penetrating Radar

Accepted Answer

EPI Geophysics offers a variety of geophysical services.  These services may be applied to residential, commercial and industrial sites in order to locate underground utilities (electric lines, water lines, telephone lines, sewer lines, gas lines, buried tanks, etc).  Drillers and building contractors frequently arrange for these services, but our tools also allow subsurface imaging that other professionals including archaeologists, geologists, hydrologists, geotechnical engineers, and environmental scientists find useful.

Ground Penetrating Radar (GPR) is the most useful of all of the geophysical tools. EPI Geophysics provides geophysical investigations to delineate subsurface features of interest utilizing high-resolution GPR antenna systems.  GPR is a fast and reliable technology using harmless microwave radiation. Data is collected systematically by this safe and non-intrusive technology.  Applications of this service include identifying and marking the location and depth of service utilities and other buried structures. Utilities to be marked include, but may not be limited to: electric, gas, telephone, fiber optics, sanitary sewers, storm drains, water service, and other metallic and non-metallic targets that include underground storage tanks (UST’s) and PVC pipes.  Project reports containing maps, photographs, and 2-dimensional images generated from post-processing are also provided as a supplemental service. 
The principle of GPR is the same as that used by police radar, except that GPR transmits electromagnetic energy into the ground. The energy is reflected back to the surface from interfaces between materials with contrasting electrical (dielectric and conductivity) and physical properties. The greater the contrast between two materials in the subsurface, the stronger the reflection observed on the GPR record. The depth of GPR signal penetration depends on the properties of the subsurface materials and the frequency of the antenna used to collect radar data.   EPI Geophysics' commitment to the safety of its employees and clients is reflected in its procurement of line locating and GPR equipment. A DPT rig and a Geophysical Investigation can be scheduled simultaneously for one day or multiple days onsite; this allows us to clear each location before any tools are advanced into the subsurface.  This higher level of confidence is invaluable when performing subsurface investigations not only for EPI Geophysics but for you and your client.

Question 2

Line Tracing

Accepted Answer

This geophysical method is used in addition to GPR, using a Vivax-Metrotech system, specifically the Loc-10Tx (10 Watt) transmitter and a VLocPro2 receiver. The system works on at least two modes including a passive mode where the receiver detects any lines carrying current as well as an induction/conduction mode.    In the induction/conduction mode, a specific radio frequency is transmitted into a cable or pipe (either through direct connection or through inductive coupling) and that same frequency is then detected with the receiver to trace the location of the buried pipe or cable.    Metal pipes are excellent conductors, therefore they frequently  pick up ambient current in the ground, which makes them good line tracing targets.  We attempt to locate all subsurface targets using at least two different methods, although for some subtle targets one method may be successful in locating targets while the other method is not.

Another way we have of tracing pipes involves sending a radio transmitter into those pipes using a Rodder/Sonde system. The pipes can be traced by tracking that radio signal with the line-tracing receiver.  For small diameter pipes that are not made of metal or some other conductive material, we can slide a wire into those pipes and transmit a radio signal into the wire which allows us to trace those pipes.

Question 3

Electromagnetic Induction Imaging

Accepted Answer

Electromagnetic Induction is a method which allows the collection of a lot of data over a broad area in a relatively short time.  It can be especially useful in Phase I work on large properties where there may be a variety of areas of concern.  It can also be useful in properties with a historic component which may be underlain by foundations, flooring, and other subsurface ruins.  Areas of fill can also frequently be defined with EM.

The EM Profiler generates a magnetic field which transmits an electrical signal into the ground.  This signal, in turn, causes an electromagnetic signal to be transmitted from the ground back up to the receiver.  EM data is collected continuously along survey lines, and each data point is associated with GPS coordinates collected at the exact same time as the EM data is collected for each point.   The data is plotted on color contour maps allowing the location of strong anomalies (like pipes, tanks, etc.) as well as weak anomalies (variations in soil saturation, compaction, etc).

The EM system makes use of lower frequency radiation than the GPR, and should be seen as a complementary tool in site assessment.  One of the big advantages of the multi-frequency system we use is that we can collect EM data from three separate frequencies (corresponding to targeting three separate depths of imaging), as well as in-phase, quadrature, and conductivity data for each of those three frequencies.  The color contour maps can be referenced in either latitude/longitude or state plane coordinates, and can also be superimposed on airborne imagery.

Question 4

GPR Scan for Residential and Commercial Real Estate Transactions

Accepted Answer

In recent years we have seen an increasing demand for GPR scanning of residential and commercial properties as a prelude to real estate sales.  Most of that work is commissioned by the buyer, but we also occasionally work on behalf of the seller.  Anyone who purchases real estate needs to be aware of the liability associated with underground storage tanks (USTs) which may lie within the property.  USTs for residential use typically supplied fuel oil to the houses.  USTs on commercial properties may also have provided storage for gasoline or diesel fuel or possibly for waste products.  Literally millions of USTs were installed during an era spanning the 1920s to the 1980s. 
EPI is able to scan your property with GPR to determine whether or not there are any USTs present.  We can scan over grass, asphalt, gravel or concrete to image what lies beneath.  Not only can we determine whether a UST is present, but we typically have the ability determine its size, shape, volume, and depth below surface.  With another set of tools that allow line tracing, we have the ability to trace piping that connects the tank to the building.  We mark all underground utilities with paint on the ground surface, and we will create a report of our findings.
 We will not only scan the areas where the UST is most likely to be located, but we will scan the entire property so that the report we submit can discuss the results for the entire property.  If no USTs are found, then the report will make that clear.  If one or more USTs are found, then we will include everything we know about the individual USTs in the report.  If you are buying a house that is more than 25 years old, and you think there is a possibility of buried tanks, then talk it over with your real estate agent and then contact us to scan the property.    You'll be glad you did.  Contact Brian or Paul at EPI Geophysics for answers to any questions or a cost estimate.

Question 5

GPS

Accepted Answer

Using a Trimble Geo7X (and accompanying Pathfinder software) we have the ability to collect precise location information on all the subsurface (or surface) features we detect.       We routinely download the mapped data to Google Earth imagery, although we can export the mapped data to other formats, as well.  In addition, if clients have coordinates of borehole location they need to locate on the ground, we can assist with that, as well.

Question 6

Archaeology

Accepted Answer

EPI Geophysics has developed a systematic approach to assessing archaeological sites using geophysical methods. The approach begins with a comprehensive 2-D Ground Penetrating Radar (GPR) survey along with an Electromagnetic Induction (EM) survey of the entire project area. The GPR survey will yield an assortment of discrete anomalies of varying sizes and depths which are marked on the ground with flags. The EM survey collects both “in-phase” and “conductivity” data at two to three different frequencies which are presented as geo-referenced color contour maps. Following the results of these two surveys, we access the area(s) most likely to be the focus of the archaeological testing and then conduct a 3-D GPR survey which will allow a unique look at the subsurface features in a variety of depth slices down to around six feet. This is a great method to image building foundations, grave shafts, privies, refuse pits, wells, etc. If the client requests it, we can also add a metal detector survey of the entire project area.

Question 7

Request a proposal or book a job

Accepted Answer

At EPI Geophysics, we do our best to work with your schedule. Our geophysists and office team create proposals to electronically sign and get your project rolling and to get you on the schedule.    To request a proposal, press here. To schedule a job, email Tony.

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