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GGI Answer: It's solely dependent upon the subsoil properties of a particular site. Each project site is different. We might be able to detect utilities and other targets up to 15' below grade at one site; but using the same equipment and the same settings, at another project site we might only be able to detect objects 4' below grade. Within our service area and a site containing excellent subsoil conditions, the maximum we'd be able to detect subsurface objects is typically 12' to 15' below grade.

GGI Answer: Radar is a unique technology in that its successful use is very dependent upon the experience, knowledge, and skill of the operator. It's not a piece of equipment that somebody can take out of the box and after reading the instruction manual execute flawless investigations. There are no universal certifications or training processes to become a "GPR operator". In our opinion, the success of detecting targets-of-concern is dependent upon the proper GPR antenna configuration and data collection procedures. We own and operate 9 different frequency GPR antenna systems ranging from 80 Mhz to 1500 Mhz. Our crews typically carry a minimum of 5 different antenna systems with them for use on every project. That way if the subsoil conditions at that particular project site are limiting the signal penetration of one antenna, we have the resources to try several different frequency antenna systems to obtain the most accurate data from the GPR system. Also, when possible, we'll correlate the GPR data with data taken using EM, Magnetics, and Radio Frequency techniques. So that a metallic tank or utility will actually be delineated 3 or 4 times, each with a different instrument, providing a "triple check" of the feature's position. In addition, our expertise is in engineering and utility industries. We know how underground utility systems, USTs, septic systems, etc. work. As a result we know what to expect and look for when confronted with complicated underground scenarios. After 1,500 nonintrusive subsurface investigations with GPR, we have fined-tuned our own exclusive data collection procedures. We know what'll work and want won't work. Bottom Line - Although subsoil conditions may prevent radar and other techniques from successfully detecting buried objects at some sites, Geo-Graf has the experience, resources, and personnel to often succeed where others have failed.

GGI Answer: Our rates are based on a per field-day basis and include site mobilization, the field investigation, site demobilization, data review and post-processing, CAD mapping, and report deliverables. The number of field days per project is dependent upon the search area size and scope of work. Cost quotes are taken on a project-per-project basis, but typical one-day project would cost $1,800 to $3,000. Please contact us to describe your project for a specific cost quotation.

Having us in for one day to investigate your proposed excavation area is usually a fraction of the cost to repair a damaged utility!

GGI Answer: Dependant upon the scope-of-work, we'll typically field-mark (paint/flags) the detected findings (with identified utilities in standard colors). Upon review and data processing at the GGI office, we'll incorporate our findings into an existing CAD mapping file (if provided) or create a new CAD map based on our field measurements. We'll prepare an Engineering Report containing a summary, scope-of-work, background, investigation description and equipment used, findings discussion, and recommendations. Also included will be selected representative GPR data profiles of significant detected features and full-color plan-view plots of the CAD map up to size ANSI E. A CD containing the CAD mapping file and digital site photographs taken by GGI will also be included in the deliverable package. Typical turnaround is 2 to 3 weeks from the last field-day.

GGI Answer: No. Not because we don't want to, but because it's technically impossible. Due to the nature of the geophysical sciences and subsoil properties beyond our control, no nonintrusive geophysical technique can be guaranteed to detect 100% of all features. What we try to do is incorporate and correlate the data from the four most reliable techniques in the industry, combine that with our unequaled "real-world" experience, to provide the best nonintrusive investigative service in the industry. All Geo-Graf work is performed under our disclaimer. What we can promise is that we'll make a professional attempt to present you with the most accurate and reliable information that can be obtained from our instruments. Even though we utilize four different nonintrusive subsurface delineation techniques for our investigations, subsurface utilities, tanks, and targets could, and do go, undetected.

GGI Answer: Absolutely! By hiring us to survey your project site before construction or excavation, we can help prevent cost overruns, work stoppages and unexpected repairs. By providing you with an accurate field-markout and utility map, knowledge of the location of near-surface rock and/or location of buried foundations, tanks, or debris prior to breaking ground, even the smallest projects can save thousands. Clients utilize our services during the design phase of projects, incorporating our findings into their plans in order to minimize potential conflicts and maximize efficiency once construction begins. Our findings are also used by bidding contractors in order to provide more accurate proposals.

Having us in to scan properties for USTs, buried drums, and other environmental hazards prior to purchasing a property can literally save you millions in liability and clean-up fees.

GGI Answer: In terms of the delineation of a utility, tank, or other feature, we're as accurate as you can paint a mark on the ground. Although we're not surveyors, the horizontal accuracy of our field-marks and CAD maps are precise enough to facilitate most excavation and construction projects. If the highest precision is needed in terms of CAD mapping and feature depth elevation, GGI recommends having a professional surveyor map our field-marks and a vacuum excavator "pot-hole" specific utilities or features to measure precise depth elevations.

GGI Answer: One-call markout is only good for specific utility company-owned lines. They markout utilities using only one technique, an RF locator, which is good for metallic utilities only. RF detection of nonmetallic lines, like PVC gas lines, can only be done if the line was installed with a "tracer wire". Often these wires are damaged during backfill or were never even placed in the same trench as the utility. At Geo-Graf, we use four different detection techniques (RF, EM, Magnetics & GPR). GPR is the only technique that can locate nonmetallic utilities like PVC, terra-cotta, fiberglass, or concrete pipes - regardless of the existence of a "tracer wire".

"I trust my prints"
Famous last words. We've lost count of how many times people swore by their prints and then we'd end up finding 2, 3, or 10 previously unknown utility systems that extend directly through their work area. In the rare case we don't happen to find any surprise utilities or anomalies and only end up verifying your existing prints, the fact that you've conducted a subsurface investigation before excavating impresses your clients, safety gurus, and insurance companies.

GGI Answer: We do not sell or rent GPR, EM, Magnetic, or RF equipment. We do not endorse or represent any specific GPR equipment manufacture.

Geo-Graf will entertain offers to purchase quality, used GPR units and antennas. Please contact us for further information.

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Updated: January 2005