Utility Locating Blog

The Use of Utility Locating Services in Hurricane Harvey’s Relief Efforts

Texas utility locating

The Use of Utility Locating Services in Hurricane Harvey’s Relief Efforts

Last week, Penhall Technologies had the opportunity to participate in the efforts for those affected by Hurricane Harvey. We performed our services at the NRG Center in Houston, which hosts the largest emergency shelter in the city.

First of all, the FDNY Incident Management Team called our Houston office for utility locating services. The New York Fire Department hired them to set up a 40’ x 100’ tent. This tent would function as the main location to serve meals to truck drivers delivering supplies for the emergency shelter itself. The NRG stadium expected over 250 truck drivers coming into Houston to deliver these supplies.

Before installing the tent, they decided to scan the proposed location for it. This was about 85,000 square feet. The scan would ensure that the client could install the tent safely, without striking any subsurface hazards. The location for the scanning took place in the parking lot.

Two of our local Houston analysts scanned for all utilities under the asphalt. They used Ground Penetrating Radar with the SIR 4000 antenna and electromagnetic detection technology through the use of the RD 7100 wand. Then, they found and marked out two utility lines. These were a sewer line and a power line.

These lines did not present any issues for the client. The analysts advised to stay a minimum of 3 feet away from the marked utilities. Due to this, the client had plenty of room left to drive the tent’s posts into the ground away from the marked lines.

Harvey utility locating

“Being able to help my community here in Houston is beyond rewarding. Helping with the utility locate at NRG makes me feel as if I’m having a direct effect on the city that I grew up in. The fact that I can give back and aid my fellow Houstonians in a time of adversity is indescribable,” said GPR analyst Jacob Paddock.

The FDNY Incident Management Team was pleased with the locating services. Since then, we have performed another locate for them in Rosharon, Texas before the installation of more tents. Their needs change daily. Therefore, they have been in constant contact with Penhall Technologies.

As a team, we are proud that our services played a role in the relief efforts. In addition, Penhall will continue to assist in any efforts that aid Texas’ recovery. To donate to those affected by Hurricane Harvey, click here.

September 8, 2017

Case Study – Utility Locating Using GPR and Electromagnetic Detection

private utility locator

GPR analyst using the RD-7000 for utility locating

When conducting utility locating services, Penhall Technologies uses two types of technology: Ground penetrating radar (GPR) and electromagnetic detection (EM). Both of these are great resources for locating underground utilities.

GPR locates underground utilities by emitting radar waves into the ground. These waves pass through the substrate and reflect off of objects that vary in dielectric from that of the surrounding earth. Ground penetrating radar works best when you need to locate: buried pipes, cables, underground storage tanks, etc.

On the other hand, electromagnetic induction detects electromagnetic fields. A magnetic field occurs when a current is running through a transmitting line such as an electrical cable or communication line. The EM unit can detect both passive and active signals.

A passive signal is when a utility, such as an electrical line, is currently turned on and is generating an electromagnetic field. An active signal is when a line is not turned on, and a temporary tone is induced into it. This creates a temporary electromagnetic field. The, the EM unit can detect this field.

Recently, our analyst put to use both technologies for a utility locating job. An electrical company contacted us for a project at a medical facility in the city of Seattle, Washington. The electrical company was in charge of rerouting electrical lines through the parking lot of the medical facility.

utility locating

Analyst marking underground utilities

The analyst initiated the scanning and set a dielectric based on the known soil conditions of the area. He conducted GPR first, utilizing the GSSI SIR3000/400MHz antenna combo. The analyst knew that once he completed the locate , the cut and excavation performed by Penhall Company would not go any deeper than three feet. The survey covered not only the requested area, but a much larger area as well to confirm the location of all subsurface hazards.

The analyst marked out several suspected utilities and an area of shallow root systems, despite needing to work around parked vehicles, tight quarters, and raised landscaping beds.

The analyst used electromagnetic detection equipment after the scan. He swept the area with the RD-7000 to ensure maximum accuracy. From this, the analyst located one additional electrical utility. This particular utility was either too small or too deep to see with the GPR equipment. This is why we provide our analysts with both technologies. It makes us the ideal private utility locator.

Penhall Technologies employs multiple technologies for your utility locating needs, making sure that you finish your projects safely and on time.

August 11, 2017

What to Expect – Home Utility Locating

Our analyst performing utility locating services

When you started your home project, you didn’t imagine that you would need our private utility locating services. To ensure that you don’t hit any utility lines, it is important to scan the area first. Damaging utility lines can result in loss of that particular utility. It can also cause injuries for you or the workers hired to do the cutting, trenching, or digging.

For home owners, utility locating can be a first and only experience. This means that it can be hard to know exactly how to proceed. The first step would be to contact 811“call before you dig”, the nationwide public utility locating service. They can locate all public utility lines, from the street to the meter only. If they can’t locate what you need, that’s when we, a private utility locator, come in.

When you call Penhall Technologies or request to quote, it is best to be prepared with essential information regarding the project. This will allow us to provide the best service and accurate pricing. It is important to know the measurements of the area, the type of surface (dirt, asphalt, concrete), and the location (indoors or outdoors). If possible, provide the utilities we may be looking for (water, gas, electrical, sewer) and how many utilities may be running through the area. We will also ask how many locations you need scanned, and what is the private line locating in preparation for.

Example of utility markings at a home


Once the analyst arrives at your home, they will be up to date with the needs and specifications of your project. They will bring two types of equipment to offer you the most accurate reading. A benefit of choosing Penhall Technologies as your private utility locator is that we carry various types of equipment. This is in case one method is not enough to find underground lines. In rare cases, the reading can be inconclusive and show highly congested results.

After the analyst completes the scan, he/she will mark the approximate utility locations with varying colors of spray paint, flags, or both to highlight that location. You can find out what each color means for utility marking in our guide here.

Equipment screen showing utility locating data

Before the analyst marks the utilities, the display screen of the equipment won’t mean much to the common eye. Our expert analysts will be able to identify lines and to differentiate between them based on the data and on physical cues, such as a meter. Now with the analyst’s markings and field report, you can make an informed decision of where to cut, trench, or dig. By deciding to scan first, you will safeguard that your home project is completed safely.

July 21, 2017

5 Factors that Affect GPR in Utility Locating

5 Factors that Affect GPR in Utility Locating

factors that affect GPR in Utility Locating

When looking for a utility line locator to locate anything from underground water lines, gas lines, electrical/power lines to underground storage tanks, it is a good idea to know the capabilities and limitations of the technologies used in those detection services.

Penhall Technologies uses both GPR, ground penetrating radar, and Electromagnetic Detection. Here, we will dive deep into GPR and what factors affect the capabilities and limitations of this technology.

  1. Weather Conditions

Because moisture raises the conductivity of the ground, especially clay soil and silt, deep snow and rain can be a factor in utility locating. Once the radar touches any ground holding moisture, it bounces right back making it tough to read anything past that water table. This can make the winter months an unideal time to do any type of locating before digging or excavating on your project.

2.  Soil Conditions in Area

Now that you know that moisture plays a role in messing with GPR data, the types of soil conditions that become a factor are those that hold the moisture the most, like clay soil or silt. Interestingly enough, sandy soils, although typically near bodies of water, are more ideal to scan over than clay soils.

Each area throughout the US have certain types of soils that are native to the area, so it is a good idea to check what the soil conditions are in your area before moving forward. Here is a helpful link to find out the suitability of GPR in your state and area.

Here is a side by side comparison between states, Florida and Utah. Utah has more clay soil vs Florida with more sandy soil.

Florida vs. Utah GPR Suitability MapGPR Suitability Index

3.  Surface Area – Clearance and Obstacles

The surface being scanned becomes a factor for GPR data when the terrain is rough enough to cause the equipment to separate from the surface more than 2 to 3 inches. The quality of the data when this happens is then compromised. Ideally, the surface needs to be reasonably flat with a good amount of clearance. Obstacles, like trees and bushes, are mainly factors that can cause a delay in the time.

4.  Limitations of Technology with Certain Materials

GPR is highly successful for locating many types of objects. That said, there are certain materials that are much more conductive and easily located than others. Metal, for example, is highly conductive, and PVC or plastic has no conductivity, which makes it more challenging to locate. PVC and other non-metallic objects do not show a signal, but rather the signal can show something inside the pipe, like air or water. The size of the PVC does impede the ability for the radar to read if it is smaller, like a 1” line. This is because the radar used is for utility locating is typically one that is too large to “see” a line that is that small. (See below – “Radar Frequency – Antenna” for more info on this.) Fisher wire/tape can be used to aide in identification in these cases.

Another factor that can impede on the GPR data is when scanning over a concrete slab with wire mesh. Because the wire mesh is metallic and the frequency of the antenna used is low and large, it inhibits the signal from penetrating clearly.

5.  Radar Frequency – Antenna
Speaking of frequency, allow us to dig deeper into how choosing the right antenna for the job is imhighest quality data with clear and accurate results.

The higher the frequency, the smaller the radar, so high frequencies are best for tighter and shallower areas. The lower the frequency, the larger the radar, so these frequencies are best for deeper penetration and larger objects like pipes. In utility locating, the antennas with lower frequencies are best.

The limitation of the antenna becomes a factor mainly when any of the above factors come into play. Also, another factor to consider is when the depth of an object needing to be located surpasses the limit of the antenna’s radar. The strongest antenna commonly used throughout Penhall Technologies can scan to a max depth of 9 feet. We find that most utilities can be found within this range. Antennas that can scan a deeper depth may be available. Please contact us directly if a deeper locate is necessary for your project.


So, there you have it. We hope that this helps to clarify any questions regarding factors that affect GPR in utility locating. When in need of utility locating services, and you’re not quite sure about the capabilities of GPR on any given project, the best approach would be to contact us directly. To best serve our customers, we will always be upfront and honest about the capabilities and limitations of our technologies, and offer any alternative approaches that we may have.

For further questions or to receive a quote:

Call or email us at:



Or visit our website:


June 19, 2017

FAQ: Private Utility Locating

private utility locating

When it comes to our private utility locating services, we know you have questions, and we have answers!


Why do I need to contact a private locator, like Penhall Technologies, if 811 is available?

It is a good idea to contact both 811 plus a private locator, like Penhall Technologies, because the 811 service will only mark those utilities that are owned by public utility companies, which many times means from the street and up to the meter only. Anything between the meter and the building is owned by the property owner, which is then considered private utilities that 811 will not mark. Learn more about the difference between public and private utility locating here.


How are cost and rates determined for private utility locating?

Pricing for our private utility locating service is unique for each project. The final cost is dependent on factors such as:

  • Job Location
  • How many utilities are being located
  • Size of the area(s) being scanned
  • What the surface being scanned is. Ex. Ground/dirt, asphalt, concrete, indoor/outdoor, etc.
  • If there are any obstructions that may impede or slow down the process. Ex. trees, bushes, bodies of water, buildings, etc.
  • Whether or not there is access to utility meters or transformer boxes

Typically, our services are offered at an hourly rate, where each location varies in their rates per hour. The above factors will help determine how much is able to be scanned per hour.


Does Penhall Technologies assume liability for any damages involving underground utilities?

Ultimately, the owner of the private utility lines on their property is required to follow their state’s One Call law before beginning any excavation or digging work. Therefore, the liability is in the hands of the property owner. Penhall Technologies will not guarantee the longevity of facility markings due to activities on site that may destroy or otherwise alter any markings placed on the ground by Penhall Technologies.

GPR and Electromagnetic Detection technologies offers the ability to determine the depth of a located object. The depth indications can vary, and there is generally a 15% margin of error.


How accurate is your utility locating?

Unlike most private locators, Penhall Technologies uses state of the art equipment using both GPR (Ground Penetrating Radar) and Electromagnetic Detection technologies. Utility markings are explained to customers by the analyst, and cutting/trenching/digging parameters are advised to be no closer than 3’ on each side of the center of the utility marker. Although exact depths cannot be provided, approximates can be discussed with, give or take 10-15% margin of error.


Can you determine the type of utility that is located?

The technologies themselves cannot determine the type of utility that is being located. That said, our expert analysts can determine the type of utilities as long as there are visible marks such as meter box, stub up, drain, manhole or cover within the proximity of the line.

Those lines that can be identified will be marked by the standardized color set by the APWA. See “Utility Locating – What Do the Colors Means?” for detail on the standardized colors for each utility here.

Those lines that have no visible signs that indicate the type of line that is located are then marked by the analyst in hot pink.


Are you able to locate non-metallic utilities such as concrete storm drains, fiber optic cables in conduit, or PVC pipes?

Yes. This all depends on the size of the pipe, depth, and soil type.


Is it true that surfaces with accumulated moisture, like clay soil or a ground with a high water table can result in inaccurate results produced by GPR, ground penetrating radar?

This can be true. Clay soil or soil with high water content can affect the GPR data and output. This is because water is conductive and once the radar picks up the moisture, it makes it tough to “read” beyond the water barrier.

The best approach is to speak to the analyst that is local to the area of the project, to better discuss the conditions of the soil in that area, as well as other options we may have.

Here is a map to illustrate the suitability of GPR throughout the United States:

GPR Suitability Map

GPR Suitability Index

At Penhall Technologies, our goal is to have our customers truly feel comfortable with choosing us as a partner in their projects. We do hope that these questions and answers are helpful.

We understand there may be more questions, so please, feel free to contact us with any further questions you may have.

For further questions or to receive a quote:

Call or email us at:



Or visit our website:


June 12, 2017

We Scan For

  • Pipes and Conduits
  • Post-Tension Cables
  • Utilities and Live Wires
  • Rebar and rebar patterns
  • Voids within the Concrete
  • Structural Integrity of the Concrete