Locating public and private underground utilities is vital to the safety of any job requiring excavation and could be the difference between finishing a construction or renovation project on time and on budget, or suffering the huge cost overruns and downtime of damage caused by a utility strike. So, it makes sense to review what is required for a clean, strike-free locate, the kinds of equipment required; and whether it makes sense to D-I-Y your locates with rental or wholly owned GPR equipment (ground penetrating radar) and electromagnetic pipe locating equipment or to hire someone to perform the locates for you.
811 One Call services are administered state by state throughout the U.S. and are required by law to locate all public utilities at any site before excavation, regardless of its scope. However, 811 locates only public utilities, not private ones, and One Call does not provide depths on its locates, only identification.
The problem is that more than 60% of all utility lines are private, which 811 will not locate, and if you attempt to dig or drill without knowing the depth of your electric and telecom lines, or your water, sewer, and gas pipes, you could knock out power to an entire neighborhood, cause a water emergency for a municipality, or cause serious injuries or death with a gas line explosion.
Anyone can rent or buy a ground penetrating radar unit and/or an electromagnetic locating system. However, just because the equipment is readily available near you does not mean you will be able to locate and map your subsurface utility infrastructure easily.
There are two major locating technologies for subsurface utility locates: ground penetrating radar (GPR) and electromagnetic locators (EM). Each has its benefits and its drawbacks, and there is a wide gap in pricing/expense between EM and GPR equipment, whether you are renting or buying it.
There are multiple kinds of locating units available, and it is important to know which kind you need for your job. For instance, GPR concrete scanning equipment, a small, handheld GPR device will not be able to accurately locate a sewer pipe three feet under the soil. An EM locator will not be able to read a PVC storm sewer line without the aid of a rodder dropped into the pipe to transmit a signal, but it can be used by itself to locate metallic pipes, while GPR can read metallic and non-metallic pipes.
The type of ground penetrating radar required to locate underground utilities has a purchase cost of somewhere between $14,000 and $100,000. As the number of available frequencies, the user interface, and GPS mapping applications expand, so does the cost. The basics of the GPR equipment, whether a single-frequency system or a multi-frequency system, consists of the wheeled base unit to roll over terrain, radar transmitter, receiver, a battery, and a user interface (software) usually read and controlled by a digital device like a tablet. Some low-cost GPR locators incorporate GPS, and higher priced equipment almost always includes GPS integration in the user interface, a larger array of attenae, and allows for multiple device access and cloud uploads.
“The type of ground penetrating radar equipment used is not a differentiator,” says GPRS Field Support Director Jamie Althauser. “Unlike laser scanners, where the equipment can make a great deal of difference, most GPR works the same way.”
Since GPR technology burst on the scene in the early 2000s, the equipment has evolved to provide a simpler, cloud-based user interface (UI), and gone are the days of 10-pound batteries that died in an hour. Past that, however, the major breakthroughs have been in functionality and convenience.
“The hardware – ergonomics – the ability to move over terrain is the most important factor,” continues Althauser.
It is possible to rent GPR equipment for the cost of approximately $400 per month, and if you are searching for a single line in a small, defined area, this maybe a viable option. However, the difference, according to Althauser and most underground utility locating professionals, is the methodology used to execute the locate.
For instance, one variety of locators is from a brand called Impulse Radar. It is among the easiest to set up, and according to Althauser, you could “use it within five minutes, but you wouldn’t know how to interpret the data.”
The stakes on a utility locate are enormous. Utility strikes can cost a great deal of time, money, and put lives at risk. According to the Common Ground Alliance, 1,100 utility damage events and/or utility strikes occur per day. So, it is imperative that a utility locator have the best training possible.
A one-day online GPR course costs about $600 at the time of this writing. However, it covers only the most basic training and does not allow for any field training where students can practice deploying GPR and learning to read the signals in a variety of conditions, and it will not certify you for the minimum industry standard.
The minimum standard for a Level 1 NDT certification is eight hours of classroom training and 60 hours of practice/field training. This minimum standard of training costs about $1,000, with a similar cost per additional training level.
By contrast, GPRS Project Managers are required to complete the SIM Certification, a multi-level process that ensures they are trained far above the minimum standard. SIM stands for Subsurface Investigation Methodology, and it is how GPRS has achieved and maintained a 99.8%+ accuracy rate on all concrete scanning and underground utility locates on over 350,000 jobs.
The SIM Certification requires 80 hours of classroom instruction and 320 hours of field training, far exceeding current industry standards. Every GPRS Project Manager is required to be SIM Certified so that they meet our rigorous locating standards. When they complete SIM training, Project Managers are experts in locating with a wide variety of equipment, including GPR and EM, which allows them to complete even the most complex locates quickly and efficiently.
Electromagnetic locating equipment has a cost of approximately $5,000. About 50% of the locating industry uses a product brand called Radio Detection (R.D.). GPRS currently deploys the Vivax V-loc Pro 3 locator. Both EM locators utilize electromagnetic frequencies to locate metallic pipes and will provide similar results, but GPRS chooses the Vivax because it provides a full-color display, and Vivax’s seamless, free GPS integration.
Like the GPR systems, EM locators are designed for ease of use, and you can rent the equipment for around $300 per week. It is important to remember, however, that the drawback to EM locating is that it cannot locate non-metallic pipes without the use of a rodder, and like GPR, requires proper training to use correctly.
The most accurate locators employ both GPR and EM in their subsurface utility locates because their experience has shown that the best way to get the job done right the first time is to use the best tool for the job. Highly trained locators understand that terrain, soil composition, age of the lines, and the location of surrounding structures are just some of the mitigating factors they need to take into consideration when scanning.
EM, while simpler to use, brings its own unique challenges for the operator. Aside from the limitation that it can only read metallic pipes, because it is a conductive technology rather than the reflective tech of GPR, you have to understand how to overcome:
When reading EM, the user is looking for the field, not the current itself, and it can be difficult to differentiate for the untrained eye, especially if that current has leapt from one pipe to another. That is why complete, accurate training is necessary for any equipment operator.
There is another way to accurately locate and verify the map of your underground utility infrastructure – hire a highly trained team of elite specialists with more than three times the expert training and experience required by most companies. When you hire GPRS, you know you’re hiring the most accurate in the business who will get the job done right – and fast – the first time.