How to Locate Underground Utilities: Methods & Best Practices
That old set of as-built drawings you have for your site might feel like a reliable map, but it’s more likely a historical document full of outdated information. Over the years, undocumented repairs, rerouted lines, and abandoned infrastructure can turn a once-accurate plan into a recipe for a costly utility strike. Relying on paper plans instead of physical verification is one of the biggest risks you can take before an excavation. This guide will show you how to move past the guesswork of old records and explain how to locate underground utilities based on what’s actually in the ground today, giving you the certainty you need to proceed safely.
Key Takeaways
- Don't mistake an 811 call for a complete site scan: The free 811 service is an essential first step, but it only marks public utilities up to the meter. You are still responsible for locating all private lines on your property, including electrical feeds to lights or water lines for irrigation.
- Use the right tools for the job: No single technology can find everything underground. A comprehensive locate requires a multi-method approach, using electromagnetic (EM) locators for metallic pipes and ground penetrating radar (GPR) to find non-conductive materials like PVC, concrete, and fiber optics.
- Treat markings as a guide, not a guarantee: The paint on the ground indicates a utility's approximate location. Always respect the tolerance zone, typically 18 inches on either side of the mark, by hand digging to visually confirm the utility's exact depth and position before using any heavy machinery.
What's Buried on Your Site? (And Why You Need to Find It)
Before the first shovel hits the ground, your project's success depends on what you can't see. Every construction site, commercial property, or campus is a complex network of buried infrastructure. Hitting a single unmarked line can bring your entire operation to a halt, creating dangerous conditions for your crew and triggering a cascade of expensive problems.
Understanding what’s underground isn’t just a preliminary step; it’s the foundation of a safe, on-schedule, and on-budget project. From gas and electric to fiber optic cables, these hidden assets are essential for modern life but pose significant risks during any kind of excavation. That’s why professional utility locating services are not a luxury, but a necessity for anyone planning to dig. Taking the time to map out the subsurface is the best investment you can make in your project’s outcome.
Common types of underground utilities
Most developed sites have a variety of buried lines, and you can’t afford to guess where they are. You’ll typically find a mix of public and private utilities, including gas lines, water pipes, electrical conduits, and telecommunication cables. Each one presents a unique hazard. A ruptured gas line can lead to explosions, a severed electrical conduit creates a serious shock risk, and a broken water main can cause flooding and massive property damage. Even hitting a communication line can disrupt critical services for an entire neighborhood and result in hefty fines. Assuming what’s buried or relying on old records is a gamble you don’t want to take.
The high cost of hitting an unmarked line
A utility strike is one of the most expensive mistakes you can make on a job site. The immediate costs of repair are just the beginning. Nationally, accidental utility strikes cost billions of dollars each year in damages, but the impact on your specific project is much more direct. You’re looking at crew downtime, equipment repairs, and potential fines from regulatory bodies. These incidents are a leading cause of project delays and budget overruns. According to the Common Ground Alliance, a single strike can have a total economic cost of tens of thousands of dollars, turning a profitable project into a financial loss overnight.
Fines, delays, and other consequences
Beyond the initial repair bill, the ripple effects of a utility strike can be even more damaging. Failing to locate private utilities before digging can cause life-threatening injuries and bring your project to a complete stop for days or even weeks. This halt in progress creates scheduling chaos for subcontractors and can damage your professional reputation. You may also face legal liability for the damages and service interruptions you caused. Accurate subsurface utility mapping is your best defense, providing the clear, reliable data you need to dig with confidence, protect your team, and keep your project moving forward without costly surprises.
The 811 Call: What It Covers and What It Misses
For anyone in construction or site management, the "Call Before You Dig" mantra is second nature. Dialing 811 is the essential first step before any excavation, designed to protect public utility infrastructure and prevent dangerous accidents. It’s a free, straightforward service that gets public utility companies to come out and mark their lines on your property, usually within a few days. This process is so ingrained in the industry that it’s easy to assume a completed 811 request means your site is fully cleared for digging.
However, relying solely on 811 can give you a false sense of security. The service has a critical blind spot: private utilities. On any commercial, industrial, or large residential property, the lines marked by 811 are only part of the story. The colorful flags and paint lines only show where public mains and service lines are located. They don't account for the complex network of privately owned infrastructure that keeps your facility running. Understanding this gap is key to preventing costly strikes, project delays, and serious safety hazards. What you don't know about what’s buried on your site can cause significant problems, but a comprehensive locating plan can keep your project on track.
How the "Call Before You Dig" process works
The national Call 811 system is a federally mandated service that streamlines the process of locating public utilities. When you contact 811 with your project details, they notify their member utility companies. Each company (like the local gas, water, or power provider) then sends a locator to your site to mark the approximate location of their underground lines using paint and flags. Contractors know this is the first step before breaking ground. The goal is to create a clear visual map of public infrastructure so you can dig safely around it.
The 811 gap: Why private utilities aren't marked
Here’s the crucial detail many people miss: 811 locators are only responsible for marking public utilities. Their legal obligation ends at the service meter or connection point. Any utility lines that run past that point are considered private and will not be marked. This includes electrical lines running to parking lot lights, water lines for an irrigation system, fiber optic cables connecting buildings, or sewer laterals. If you’re working on a commercial campus, industrial facility, or even a large residential property, your site is almost certainly full of private utilities that 811 will not identify.
When to call a professional locator
To find what 811 misses, you need to hire a private locator. Professional crews use advanced equipment like electromagnetic (EM) locators and ground penetrating radar (GPR) to detect both metallic and non-metallic lines across your entire site. Unlike the free 811 service, private utility locating services provide a complete picture of all buried infrastructure, public and private. This comprehensive approach is the only way to ensure your excavation plan is based on complete, accurate data, protecting your team, your budget, and your timeline from the consequences of an unexpected utility strike.
An Overview of Utility Locating Methods
When you need to know what’s underground, professional locators don’t just rely on one tool. They use a combination of technologies to build a complete and accurate picture of your site. Each method has its strengths and is designed to find different types of utilities. Understanding the basics of these techniques can help you appreciate what goes into a thorough site scan and why a multi-method approach is so important for preventing costly strikes. Let's look at the most common methods used in the field.
Electromagnetic (EM) locating
Electromagnetic (EM) locating is the most widely used method for finding conductive utilities like metal pipes, cables, and tracer wires. The process works by sending a radio frequency from a transmitter into the ground. A handheld receiver then picks up this signal as it travels along the buried line, allowing a technician to trace its path and depth. It’s a reliable technique for most metallic infrastructure and a foundational part of any utility locating service. Its main limitation is that it can’t detect non-conductive materials like plastic or concrete.
Ground Penetrating Radar (GPR)
This is where Ground Penetrating Radar (GPR) comes in. GPR is the key to finding non-metallic lines that EM locators can’t see. It works by sending high-frequency radio waves into the ground and measuring the reflections that bounce back from buried objects. This creates a real-time image of the subsurface, revealing everything from PVC and fiber optic lines to underground storage tanks. GPR is especially critical on complex sites with unknown materials, providing the data needed for comprehensive subsurface utility mapping and helping you avoid surprises during excavation.
Passive locating
Passive locating is different because it doesn't require a transmitter. Instead, this method involves "listening" for the electromagnetic fields already being emitted by live, energized lines like active power cables. A technician uses a receiver to detect these existing signals, which confirms the presence and location of a live utility. It’s an excellent way to verify findings from other methods or to identify active lines without making a direct connection. This technique adds another layer of certainty to a thorough site scan.
Acoustic detection
Acoustic detection is a specialized method used to find leaks in pressurized pipes, like water mains or gas lines. It operates on a simple principle: a leaking pipe creates a distinct sound. Sensitive listening devices are placed on the ground to pick up these sounds, allowing a technician to pinpoint the exact location of a break. While not used for general utility mapping, it’s an invaluable tool for maintenance and diagnostics, helping prevent small leaks from becoming major problems on your site.
How Does Electromagnetic (EM) Locating Work?
Electromagnetic (EM) locating is one of the most reliable and widely used methods for finding buried utilities. Think of it like a targeted radio broadcast. A transmitter sends a specific frequency through the ground, and a receiver picks up the signal that radiates from a conductive pipe or cable. This allows a skilled technician to trace the path of the utility with a high degree of accuracy.
Because it relies on conductivity, EM is the go-to method for locating metallic lines. It's a foundational part of any comprehensive site scan and is often the first tool we use in the field. When combined with other technologies, our utility locating services provide a clear picture of what’s happening beneath the surface, so you can plan your project with confidence. The process is fast, efficient, and essential for preventing dangerous and costly utility strikes.
Active vs. passive EM detection
EM locating isn't a one-size-fits-all process. It can be performed in two ways: active and passive. Active locating is the most precise method. Here, a technician intentionally applies a current to a utility line. This can be done by directly connecting the transmitter to a known point, like a valve or meter, or by using an inductive clamp. The receiver is then tuned to that specific frequency, which filters out background noise and allows for a clear trace of the target line. This is the best way to isolate and map a specific utility.
Passive locating, on the other hand, involves listening for signals that are already present on a line. For example, a live electrical cable emits its own frequency that a receiver can detect without a transmitter. It’s a great way to do a quick sweep of an area to identify potential power lines, but it’s less precise and can’t find de-energized lines or pipes without a natural signal.
What utilities can EM find?
The key to EM locating is conductivity. If a utility can carry an electrical current, EM can likely find it. This makes it extremely effective for a wide range of common underground infrastructure. Technicians can easily locate metallic pipes for water, sewer, and natural gas, as long as the gas lines have a conductive tracer wire installed alongside them. It’s also the primary method for finding live electrical cables, telecommunication lines for phone and cable, and even irrigation systems with metallic components.
However, EM technology cannot directly detect non-conductive materials. Utilities made from PVC, concrete, or asbestos cement are invisible to EM scanners unless they were installed with a tracer wire. This is a critical limitation to understand and a major reason why relying on a single locating method can leave you with an incomplete picture of your job site.
How soil conditions affect EM scans
While EM is a powerful tool, its performance can be influenced by what’s happening in the ground. Soil conditions play a big role in signal quality. Highly conductive soils, like dense clay or wet ground, can cause the electromagnetic signal to disperse or "bleed off" onto surrounding soil instead of staying on the target utility. This can make the signal weaker and harder to trace accurately.
Other site features can also cause interference. Large metal objects buried nearby, such as old tanks, rebar in concrete, or even chain-link fences, can distort the signal and lead to false readings. This is where expertise makes all the difference. An experienced technician can recognize the signs of interference and adjust their technique to get a reliable reading. This is also why a comprehensive subsurface utility mapping approach, which often combines EM with GPR, is the best way to confirm findings and account for site-specific challenges.
What Is Ground Penetrating Radar (GPR) and When Is It Used?
While electromagnetic locators are fantastic for finding conductive metal pipes and cables, they can’t see everything buried on your site. That’s where Ground Penetrating Radar (GPR) comes in. Think of it as an ultrasound for the earth. It provides a non-invasive way to see what’s happening underground, making it an essential tool for creating a complete and accurate picture of your job site. By using GPR, crews can identify utilities that other methods would miss entirely, preventing dangerous and costly surprises during excavation.
The basics of GPR technology
GPR works by sending high-frequency radio waves into the ground from a surface antenna. When these waves hit a buried object or a change in material, they bounce back to a receiver. This process creates a detailed, real-time image of the subsurface, almost like a vertical slice of the ground. Our expert technicians analyze these reflections to identify the location and depth of buried utilities, voids, rebar, and other features. This technology allows us to perform detailed GPR scanning that maps out underground infrastructure without ever breaking ground, giving you a clear view before you dig.
Why GPR is essential for non-metallic lines
Modern construction relies heavily on non-metallic materials, and this is where GPR truly shines. Traditional locating methods that rely on electrical currents are completely blind to materials like PVC, concrete, asbestos cement, and fiberglass. GPR is the go-to solution for finding plastic water lines, fiber optic conduits, concrete storm drains, and even underground storage tanks. As more infrastructure is built with these non-conductive materials, using GPR is no longer optional; it’s a critical step for any comprehensive subsurface utility mapping project. It fills the gaps left by other technologies, ensuring all utilities are accounted for.
GPR vs. EM: Which tool for which job?
So, when do you use GPR versus an EM locator? The answer is often both. EM locating is the most common method and works perfectly for finding conductive utilities like metal pipes and tracer wires. GPR, on the other hand, is the ideal tool for locating non-metallic lines and verifying findings in congested areas. However, GPR does have limitations. It can struggle in dense, clay-based soils or highly saturated ground. An experienced locator understands the strengths and weaknesses of each tool and will use them together to cross-reference findings and produce the most accurate results possible for your project.
Avoid These Common (and Costly) Locating Mistakes
Knowing what’s underground is the first step, but how you get that information matters just as much. Even with the best intentions, a few common missteps can lead to inaccurate locates, project delays, and dangerous utility strikes. The good news is that these mistakes are entirely avoidable when you know what to look for. By sidestepping these common traps, you can ensure your project stays safe, on schedule, and on budget. Let's walk through the four biggest locating mistakes we see in the field and how you can steer clear of them.
Relying on outdated site plans
It’s tempting to treat old as-built drawings or site plans as gospel, but they are often a recipe for disaster. These documents can be decades old and may not reflect undocumented repairs, rerouted lines, or abandoned utilities left in the ground. One of the most frequent challenges in this industry is working from incomplete or inaccurate records. Relying on them can lead to false assumptions about a utility's position and depth. Think of old plans as a historical reference, not a current map. They provide clues, but they should never replace a physical, on-site investigation to create an accurate subsurface utility mapping of your project area.
Using only one detection method
There is no single tool that can find everything underground. A common mistake is depending on just one technology, like EM, and assuming it will catch every potential hazard. This approach leaves major blind spots. For example, an EM locator is great for finding conductive metal pipes and tracer wires, but it will completely miss non-metallic lines like PVC, asbestos cement, or concrete. This is why a multi-method approach is so critical. By combining technologies like Ground Penetrating Radar (GPR) and EM, a skilled technician can cross-reference data to build a much more complete and reliable picture of what’s actually buried on your site.
Guessing utility depths
Finding a utility’s horizontal location is only half the battle. Guessing its depth is one of the riskiest assumptions you can make before excavating. Surface marks only tell you where a utility is, not how deep it is. Depths can vary significantly across a site due to changes in grade, erosion, or previous construction work. Never assume a line is buried deeper than your excavation plan. The only way to be certain is to physically verify the depth through non-destructive methods like potholing or vacuum excavation, especially when digging within the designated tolerance zone. This simple verification step is key to avoiding costly strikes and keeping your team safe.
Underestimating the need for expertise
Advanced locating equipment is powerful, but it’s only as effective as the technician operating it. The ability to interpret GPR data or distinguish a faint EM signal from background noise is a skill that comes from years of field experience. An expert technician understands how different soil conditions affect the equipment and can recognize subtle patterns that point to an unmarked utility. Simply renting a tool for the day isn’t a substitute for professional expertise. The accuracy of your locate depends heavily on the person behind the equipment, which is why partnering with a team of skilled professionals is one of the best investments you can make in your project’s safety and success.
Your Pre-Excavation Checklist: 4 Steps Before You Dig
Before the first shovel hits the ground, a little prep work goes a long way in preventing costly strikes, project delays, and safety hazards. Even with advanced technology, utility locating has its challenges. Following a clear checklist ensures every dig starts on the right foot, protecting your crew, your budget, and your timeline. Think of these four steps as your project’s essential foundation for a safe and successful excavation.
Create a solid excavation plan
A comprehensive excavation plan goes beyond just marking a spot on a map. It involves defining the scope of your dig, understanding the site's history, and anticipating potential obstacles. Your plan should include a schedule, safety protocols, and a clear strategy for what to do if you encounter an unexpected utility. The first step is always getting a professional assessment. Because public locators only mark utilities up to the meter, incorporating private utility locating into your plan is critical for identifying everything else buried on-site. This proactive step ensures your team has a complete picture before breaking ground.
Coordinate with all stakeholders
Clear communication is the backbone of safe excavation. Before work begins, make sure every stakeholder, from the general contractor and subcontractors to the property owner and facility managers, is on the same page. Everyone involved should have access to the excavation plan and the most current utility maps. This alignment prevents dangerous assumptions and ensures that safety markings are respected. Encouraging open dialogue and participating in damage prevention initiatives helps identify potential issues early on. A pre-dig meeting is a great way to review the plan, walk the site, and confirm that everyone understands their role and responsibilities.
Get your permits and paperwork in order
Navigating the necessary paperwork is a non-negotiable step. Your first action should always be submitting a locate request by calling 811 a few days before you plan to dig. This service is free and prompts public utility companies to mark their lines on your property. However, remember that 811 is only the beginning. You may also need excavation or construction permits from your local city or county, depending on the project's scale. Failing to secure the right permits can lead to hefty fines and immediate work stoppages, so it’s crucial to get all your documentation in order well before your start date.
Understand regulatory compliance
Knowing and following the rules isn’t just about avoiding fines; it’s about keeping people safe. Your project must adhere to regulations set by the Occupational Safety and Health Administration (OSHA) for trenching and excavation safety. Beyond federal laws, it’s wise to follow industry best practices established by organizations like the Common Ground Alliance (CGA). These guidelines provide a clear framework for everything from how utilities should be marked to the procedures for digging safely near buried infrastructure. Compliance protects your crew from harm and your company from serious liability, making it an essential part of any pre-excavation checklist.
How to Read Utility Markings and Dig Safely
Once a site has been scanned and marked, your team can finally get to work, right? Almost. Professional utility locating is the first step, but understanding the results and digging safely is just as important. The paint, flags, and digital maps are your guide to preventing dangerous strikes, costly repairs, and project-stopping delays. Following a few key principles ensures that the data gathered during the locating process translates into a safe, efficient excavation.
A guide to APWA color codes
Those colorful lines painted on the ground aren’t random. They follow a universal system created by the American Public Works Association (APWA) to identify what’s buried below. Learning this color code is essential for anyone working on an excavation site.
Here’s a quick guide to what each color means:
Red: Electric power lines, cables, and conduits
Yellow: Gas, oil, steam, and other flammable materials
Orange: Communication lines (like fiber optics), alarm cables, and signal lines
Blue: Potable (drinking) water
Green: Sewer lines and storm drains
Purple: Reclaimed water, irrigation lines, and slurry lines
White: Proposed excavation routes and limits
Pink: Temporary survey markings
Think of these colors as a universal language for the job site, keeping everyone informed and safe.
Respecting the tolerance zone
A painted line on the ground marks the approximate location of a utility, but it’s not an exact science. That’s why regulators and safety experts established the tolerance zone. This is a critical buffer area extending from the outer edges of a marked utility, typically 18 inches on either side. Within this zone, you should never use mechanical digging equipment like an excavator or a backhoe. The risk of striking the line is simply too high. Adhering to the tolerance zone is a non-negotiable rule for utility damage prevention and is the best way to protect both your crew and the infrastructure you’re working around.
Hand digging vs. mechanical excavation
So, if you can’t use machines inside the tolerance zone, how do you expose the utility? The answer is careful, manual excavation. Using hand tools like shovels to "pothole" or "daylight" a utility is the industry standard for safely verifying its exact horizontal and vertical position. This process allows you to see the utility with your own eyes before any heavy equipment gets close. While it requires more patience and effort upfront, hand digging is infinitely cheaper and safer than repairing a severed fiber optic cable or a ruptured gas line. It’s a critical step in any responsible excavation plan and a core part of our utility locating services.
How to Choose the Right Locating Method for Your Project
Picking the right tool for the job is everything in construction, and utility locating is no different. The method you choose can make or break your project's timeline and budget. There isn’t a single magic wand that finds everything, so understanding your options is the first step toward a safe and successful dig. Accurate locating is essential for preventing damage and keeping your crew safe. Let’s walk through what you need to consider to get clean, reliable results every time.
Key factors that influence your choice
Choosing the right locating method helps your entire project succeed. Before work begins, think about a few key details. First, what kind of utilities do you expect to find? Conductive metal pipes and tracer wires are perfect for electromagnetic (EM) locators, but non-metallic lines like PVC, concrete, or fiber optic cables will require Ground Penetrating Radar (GPR). Next, consider the scope of your project. Are you clearing a single spot for a soil boring or mapping an entire site for a new build? The size and complexity of the job will determine which combination of utility locating services you need. Finally, what does the site history tell you? Old, abandoned lines or inaccurate as-builts mean you’ll need a more thorough investigation.
Why a multi-method approach is best
One of the biggest mistakes you can make is relying on a single technology and assuming it will detect everything. No single technique can identify every type of underground utility, which is why a multi-method approach is the industry standard for accuracy. Think of it as getting a second opinion for every target. EM locators are great at tracing a specific line, but they can’t see non-conductive pipes. GPR can detect those non-metallic targets and provide a visual cross-section of the ground, but its signal can be limited by site conditions. Using both methods allows technicians to cross-reference data, confirm targets, and find utilities that one tool alone would have missed. This comprehensive process is the foundation of subsurface utility mapping and gives you the highest level of confidence before you break ground.
How site conditions impact accuracy
The ground itself can be your biggest challenge. Soil composition, moisture levels, and surface interference all play a role in the accuracy of a scan. For example, GPR works best in dry, sandy, or low-conductivity soils. In dense, wet clay, the radar signal gets absorbed quickly and can’t penetrate as deeply. Both EM locators and GPR can also suffer from signal interference caused by nearby metal objects like rebar, chain-link fences, or active power lines. An experienced field technician knows how to recognize these challenges and adjust their equipment and approach to filter out the noise. They can interpret complex data and differentiate a real utility from background interference, ensuring the marks on the ground are trustworthy.
When Should You Hire a Professional Utility Locator?
Calling 811 is the essential first step for any excavation project, but it’s just that: a first step. The public utility companies will mark their lines up to your property meter, but anything beyond that point is considered private. This includes water lines running to a building, electrical conduits for parking lot lights, or fiber optic cables connecting different facilities on a campus. Unfortunately, these private utilities fall outside of 811’s scope, leaving a dangerous information gap for anyone planning to dig.
This is precisely when you need to bring in a professional. If you’re trenching for new installations, planning soil borings, or upgrading a commercial site, you are responsible for identifying and protecting any private lines. Relying on outdated as-builts or assuming you know what’s buried is a recipe for disaster. A professional private utility locating service uses advanced technology to fill in the blanks left by the 811 system. They provide the comprehensive, field-ready data you need to keep your project safe, on schedule, and on budget. Think of it as a critical due diligence step before breaking ground.
The benefits: Accuracy, speed, and safety
Hiring a professional locator isn't just about checking a box; it's about protecting your entire project. The primary benefit is safety. Accidentally striking a gas line or a high-voltage electrical conduit poses an immense risk to your crew and the public. Professionals use advanced equipment like Ground Penetrating Radar (GPR) and electromagnetic (EM) locators to accurately identify buried infrastructure, preventing dangerous and costly accidents.
Beyond safety, you gain speed and accuracy. A dedicated crew can scan your site and deliver clear, reliable markings quickly, preventing the kinds of delays that throw timelines off track. This accuracy is essential for successful construction and avoids the financial losses that come with utility disruptions or repair work. It’s the difference between moving forward with confidence and guessing what lies beneath the surface.
Understanding the cost and ROI
It’s easy to look at professional locating as just another line item on the budget, but it’s better to view it as project insurance. The upfront cost of a thorough site scan is minimal compared to the staggering expense of a utility strike. Repairing a severed fiber optic cable or a broken water main can cost tens of thousands of dollars, not to mention the project delays and potential regulatory fines.
The return on investment becomes clear when you weigh the cost of the service against the risks you’re avoiding. As experts often say, using professional locating services costs far less than fixing a damaged utility. By investing in a comprehensive subsurface scan, you’re not just buying data; you’re protecting your budget, your schedule, and your team from preventable disasters.
How to choose the right locating partner
Not all locating services are created equal. When selecting a partner, look for a team with proven expertise and the right tools for your specific site conditions. A truly professional locator is skilled in using multiple technologies, from EM locators for conductive pipes to GPR scanning for non-metallic lines like PVC or concrete. This multi-method approach ensures they can find everything, including old or unknown utilities that don’t appear on any plans.
Ask about their process and deliverables. Do they provide clear, color-coded markings on-site? Can they deliver a detailed digital map of their findings? You should also prioritize responsiveness. Look for a company that gives you direct access to their experts, not a call center. The right partner acts as an extension of your team, delivering the clean, engineer-ready results you need without delays.
Frequently Asked Questions
I always call 811 before a project. Why do I need to hire a private locator too? Calling 811 is the perfect first step, and it’s required by law. However, the 811 service only locates public utilities, meaning the lines owned by utility companies up to your property’s meter. Any lines that run from the meter to your buildings, parking lot lights, or irrigation systems are considered private. You are responsible for locating these private lines, and that’s where a professional service comes in to map the rest of your site.
What's the difference between EM and GPR? Do I really need both? Think of it this way: Electromagnetic (EM) locating is fantastic for finding conductive metal pipes and cables by tracing a specific electrical signal. Ground Penetrating Radar (GPR) acts more like an ultrasound for the ground, creating an image of what’s below. GPR is essential for finding non-metallic lines like PVC, concrete, or fiber optic cables that EM can’t see. Using both methods together is the best practice because it allows a technician to confirm findings and create the most complete map of all buried infrastructure.
How accurate are the paint marks on the ground? The markings are very accurate, but they indicate the approximate location of a utility, not its exact position down to the inch. This is why every marked line has a "tolerance zone," which is typically an 18-inch buffer on either side of the mark. Within this zone, you should only use non-destructive methods like hand digging to carefully expose the utility and visually confirm its depth and location before any mechanical equipment gets close.
Can you find utilities that aren't on any of my site plans? Yes, absolutely. This is one of the most important reasons to get a professional scan. As-built drawings and site plans are often outdated and don't show undocumented repairs, rerouted lines, or abandoned infrastructure left in the ground. Our equipment detects what is physically present beneath the surface, giving you a real-world map of your site, not just a historical record.
Is professional locating really worth the cost for a small project? It’s best to think of professional locating as project insurance. The cost of a single utility strike, even on a small job, can be devastating. When you factor in repair costs, crew downtime, and potential fines, the expense of a strike can easily dwarf the upfront cost of a professional scan. Investing in a locate protects your budget and schedule from a preventable accident, no matter the size of your project.