The Proper Approach to Utility Locating is No Accident!

One of the most dramatic evolutions is that of Ground Penetrating Radar (GPR) technology. GPR is today a valuable and essential tool for utility locate professionals. When one considers the ramifications of digging, drilling, or trenching in undesignated areas, or in areas that have been designated but without utilizing all of the available locate technologies, you have to wonder…are underground conflicts really accidents?

There are no Accidents!

The first reaction to such a bold statement is usually resistance since most people can identify events that they seemingly have absolutely no control over. To completely grasp this concept is a matter for another discussion and one based more on philosophy and reasoning.

However, when one considers the ramifications of digging, drilling, or trenching in undesignated areas, or in areas that have been designated but without utilizing all of the available locate technologies, you have to wonder…are underground conflicts really accidents? Or are these conflicts a series of preventable missteps that lead to what in some cases are catastrophic events as is commonly reported in industry publications and the common press.

Technology Improvements

The last decade has seen amazing improvements in the technology available for locating underground utilities and the awareness of how each should be used. One of the most dramatic evolutions is that of Ground Penetrating Radar (GPR) technology. Amazingly, there are still many “accidents” that occur in areas that were designated (located and marked-out) with traditional electromagnetic (EM) locating tools only. A high percentage of these unfortunate events involve what some still consider unlocateable services such as plastic pipes.

GPR technology is no longer the newcomer to the utility locating industry anymore. The value of this technology to the utility industry is incalculable. For many years the term unlocateable was generally applied to buried utilities constructed from materials such as plastic (HDPE, PE, PVC), concrete, terracotta/ clay, transite, asphalt composite, non-toneable fiber and more. No longer! Today not one of these materials is considered unlocateable in ground conditions suitable for GPR.

How does GPR work?

GPR works by sending out a tiny pulse of high frequency radio wave energy from a transmitting antenna element that is positioned at the ground surface. A receiving antenna element then records the strength and the time required for the return of any reflected signal. A series of pulses over a single area make up what is called a GPR scan. Reflected signals (reflections) are produced whenever the energy pulse enters into a material with different electrical conduction properties (dielectric permittivity) from the material it left, i.e. from soil to PVC pipe. The PVC has a different dielectric permittivity than the surrounding soil and will therefore reflect some of the energy pulse. Reflected energy detected at the surface is digitized before being processed through a control unit to a display/ storage device.

GPR systems are now available in many system configurations and within a price range that easily justifies any cost/ benefit analysis approach. For example, MALÅ the global leader in the design, manufacture and sales of GPR products, offers its entry level Easy Locator starting at less than US $12,000. The Easy Locator in particular, was developed to specifically address the needs of those involved in utility locating and at a low cost. Locate professionals using traditional EM locators are accustomed to products that are user friendly, field rugged and highly portable, and therefore demand similar features when looking for GPR equipment and MALÅ products consistently satisfy in this regard.

For more sophisticated utility investigations where there is a need to publish accurate maps by Subsurface Utility Engineering (SUE) firms, mid to high-end GPR systems are fully capable and are frequently employed for the storage of survey data. GPR data is commonly collected by scanning an area designated in a grid and this survey data is stored in the instrument for post processing and analysis and of course the production of detailed utility maps.

Subsurface Utility Engineering (SUE)

One such company is SoftDig Underground Services, Inc. based in West Chester, Pennsylvania, USA. Edward Hilbush, Jr., President of SoftDig was not only one of the early pioneers of the SUE process, but he himself developed the first vacuum excavation rig for use to non-destructively and safely expose buried utilities as part of the locate process.

SoftDig was an early adopter of GPR many years ago; even when systems were a bit more cumbersome and expensive and seemingly designed for use by a specialist in GPR rather than a field technician charged with performing standard utility locates. As Ed Hilbush comments “the need for GPR in our industry was obvious once we had a clear understanding of its capabilities.” However, some years ago the need did not always justify the cost and complexity involved. At the time of writing, SoftDig has a fleet of GPR systems out in the field and are readily available on every project as needed. As Mr. Hilbush describes it “SoftDig considers GPR a valuable tool to offer our diverse cliental base. The MALÅ unit is rugged, easy to operate, and dependable.”

SoftDig has a litany of projects validating the essential use of GPR to provide answers and find “unlocateable” underground utilities and other facilities. SoftDig was recently challenged to designate all utilities at a very exclusive Golf & Country Club in the northeast USA, as part of a SUE project for planned upgrades to the facility. Part of the project demanded the detection and mapping of both a 4” PVC water pipe and a gravity sewer line. Not only did the pipes run under the club’s parking lots, but more importantly they also traversed several fairways of the golf course. The lack of cleanouts for access to the sewer line and the material construction of the pipes themselves left only one locate technology option…GPR. Actually, before GPR there was another option; one could simply have potholed along the fairways until the lines were exposed. It is pretty obvious that in this instance, this was a less than desirable approach.

The MALÅ Easy Locator was used to quickly scan the areas of interest and with minimal effort both lines where accurately designated and the positions later translated into permanent drawings. This is a clear example of how GPR fits into a project scheme.

Over the years, Dennis Cinneli and Larry Verga of EastCom & Associates of New Jersey, USA, have worked closely with SoftDig to supply both MALÅ GPR and traditional EM locating equipment to the company. Cinneli and Verga both universally agree with Mr. Hilbush that GPR is now an essential locating tool in the field. As seasoned veterans in supplying SUE firms, locate companies, and utility companies alike with the latest in technology they are not surprised with the many success stories involving GPR.

Review

Let us now refer back to the original premise about whether an event qualifies as an accident. One has to wonder for example that if a horizontal directional drilling (HDD) machine was employed and had intercepted one or both of the PVC lines under the fairway, what the press headlines would read. Would the headline in the local newspaper read “Accidental Rupture of Water Line Leaves Massive Sinkhole in Fairway, Course Closed for Several Months”? One has to believe that this is exactly how the incident would be reported. Assuredly, it is no accident that GPR is now prevalent in the utility locate and mapping profession.

Conclusion

The information presented above once again demonstrates that GPR is a versatile, accurate, reliable and even more an essential tool that can save significant time and money for locate professionals.

However, it is worth noting in conclusion that whilst GPR is an effective locating tool, as clearly demonstrated; unfortunately, it doesn’t work in all areas! GPR is not a “magic wand” and has its limitations like any tool. GPR works best in soils or medias that are non-conductive, so it does not work equally well in all soils (soils can range from very favorable to unfeasible). As a general rule of thumb, soils with high mineralogical clay content inhibit the performance of the GPR signal, whilst sandy or gravely soils are much more suited to the method.

Brian Wright
Sales & Marketing Manager