Did you know the United States boasts 160,000 miles of high-voltage power lines? That’s on top of its millions of miles of low-voltage utility lines and transformers. A massive chunk of these power grid components lies beneath the ground.
Similarly, the country’s drinking water infrastructure system has 2.2. million miles of buried pipes. Many other utilities, like gas, sewer, and communication, also have underground lines.
So if you start digging without knowing what’s below, you risk hitting a utility line. If this happens, you can disrupt or lose the service provided by that line or structure you hit.
Fortunately, there are ways to detect and mark underground utility lines. So keep reading, as we’ll tell you about the most common ones in this guide.
The National 811 Service
Suppose you’re planning an outdoor home improvement project that requires digging. This may include planting trees or shrubs and installing a fence, mailbox, or pond. If you live in the United States, you must call 811 first.
In 2005, the Federal Communications Commission (FCC) established 811 as the national before-you-dig-number. It’s the country’s primary utility line locator service. Managed by the Underground Service Alert (USA), it’s free and available to anyone in the U.S.
When you call 811, you place a request to have the locations of buried utilities identified. The USA will then contact the utility companies possibly servicing your area. Those that do will go to you and mark their buried service lines with paint or flags.
It’s important to note that utility companies only mark public utility lines. These include lines from roads to specific service points or meters. So lines from the road to your gas, water, or electric meter are public.
Everything else that extends beyond service points and meters is already private. This means you own them, so utility companies will not mark them.
Underground Utility Line Detection Equipment
Utility locating companies use sophisticated equipment to find underground lines. You can hire them for projects involving digging in areas with private utility lines. You can also seek their help if you must start your project ASAP (811 services can take several days, even weeks).
Here are some of the most common equipment utility locating companies use.
Underground Magnetic Locators
Underground magnetic locators can locate ferrous metals, such as iron or steel.
Magnetic locators look for a difference in the Earth’s magnetic field. Iron-rich objects, like iron or steel valves, can generate this difference. The Earth’s magnetic field affects them, causing them to create magnetic fields themselves.
To do their job, magnetic locators use a transmitter and receiver.
A transmitter’s job is to generate a specified frequency or signal. This signal then gets applied to an area where they may be a buried ferrous object.
Let’s say that the frequency or signal reaches an iron or steel pipe. The line then reacts by generating a frequency or signal itself. The underground locator’s transmitter then detects that reaction.
As a result, the transmitter can determine the utility line’s placement. It then “communicates” with the receiver, telling it of its findings.
The receiver’s job is to receive the signals sent by the transmitter. Then, it shows the information on its display screen. The operator can view these details to learn where the buried line is.
Some of the most innovative underground magnetic locators can work on depths of up to 360 feet. Their advanced signal processing and communication designs also allow for more accuracy. You can click here for locators offering such features and specifications.
Electromagnetic (EM) Locators
While also called pipe and cable locators, EM locators don’t actually “see” the pipes and cables. Instead, they detect the electromagnetic field surrounding these lines. They work similarly to magnetic locators but are specifically for pipes and cables.
EM locators can find phone, electrical, CATV, gas, water, and steam lines. They can also detect security, fire, and lighting systems. They do so either through their active or passive mode.
Active mode is more commonly used than passive mode. It involves using an EM transmitter to apply a signal on underground utilities. An electrical current flows onto the line, generating a cone-shaped magnetic field.
The EM receiver then detects that magnetic field. That allows the operator to determine the presence of a pipe or cable in that area.
Utility locators often only use passive mode on utility lines with locatable signals.
Standard EM locators also often feature cable avoidance tools (CATs). CATs help identify the location of underground cables and pipes before excavation. As a result, diggers can avoid them, lowering the risk of injury or utility damage.
More advanced EM locators have features that provide even more precise readings. For example, they can detect utility lines buried deeper and track their course. Some even let you create accurate maps in 3D.
Ground Penetrating Radar (GPR) Equipment
GPR equipment can accurately locate the position of an underground object. It can also help determine the object’s depth. Depending on its accuracy, it can give readings within 10% of the actual depth.
GPR accuracy depends on soil conditions, though. For example, it can see very deep in sand and sandy soils. By contrast, it has a limited penetration depth in clay soils.
GPR equipment works by using radar pulses to detect underground objects. These include metallic and non-metallic (e.g., plastic, fiberglass, or concrete) utility lines. It can also locate other things, such as underground storage tanks, boxes, and vaults.
Asbestos is another non-metallic material that GPR equipment can detect. This makes its use even more crucial, considering asbestos causes deadly diseases. About 1.3 million general industry and construction workers in the U.S. are at risk of asbestos exposure.
Never Hit a Utility Line
Remember: Hitting a utility line can lead to service outages and severe injuries. Even if you don’t get injured, you’ll likely face penalties, high repair costs, and hefty fines. So, always call 811 or a private utility locating company before you dig.