Subsurface Line Locating: Finding What 811 Misses

Nothing brings a project to a screeching halt faster than the sound of an excavator hitting an unmarked pipe. The consequences are a project manager’s nightmare: costly repairs, dangerous safety risks, crew downtime, and blown schedules. While many see pre-excavation scanning as just another box to check, it’s actually one of the most effective forms of risk management you can invest in. Professional subsurface line locating is about more than just finding pipes; it’s about protecting your budget, your timeline, and your team. This guide explains how the process works, what we can find, and how it provides the certainty you need to dig with confidence.

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Key Takeaways

• Always supplement the 811 call: The free public service only marks utilities up to your meter. A private locate is necessary to find all the private lines on your property, like power to outbuildings or irrigation lines, which are a common cause of utility strikes.
• Technology determines what gets found: A comprehensive locate requires multiple tools, since methods like EM locating cannot find non-metallic lines like PVC or fiber optics. A professional service uses GPR and other technologies together to create a complete and accurate map.
• View private locating as project insurance: The cost of a professional scan is a small investment compared to the massive expense of a utility strike. Preventing just one incident saves you from repair bills, project delays, and serious safety risks.

What Is Subsurface Line Locating?

Subsurface line locating is the professional practice of finding and mapping underground utilities before you start a project. Think of it as creating a detailed blueprint of everything buried beneath the surface, from water pipes and gas lines to electrical and fiber optic cables. Instead of relying on outdated records or guesswork, this process uses a combination of advanced geophysical methods and records research to give you a clear, field-ready picture of what you’re working with. It’s a critical part of what engineers call Subsurface Utility Engineering (SUE), a practice designed to manage the risks associated with underground infrastructure.

The goal is simple: to reduce uncertainty and prevent problems. By knowing exactly where utilities are located, you can design your project with confidence, prevent dangerous accidents, avoid costly repairs, and keep your schedule on track. Unlike the free 811 service, which only covers public utilities, a private subsurface utility mapping service provides a comprehensive look at everything on your site, including the lines that 811 misses. Whether you're planning soil borings, trenching for new fiber, or upgrading a facility, it’s an essential step for any project that involves breaking ground.

The Risks of Digging Blind

Hitting an unmarked utility line is one of the fastest ways to derail a project. The consequences range from inconvenient to catastrophic. A severed fiber optic cable can knock out internet service for an entire campus, while striking a water main can cause massive flooding and service disruptions. Even worse, hitting a gas or electrical line can lead to serious injury or death.

Beyond the immediate safety hazards, the financial fallout can be staggering. You’re not just looking at repair costs; you’re facing project delays, crew downtime, and potential fines. These unexpected problems create a domino effect that impacts your budget and your timeline. A professional locate helps you avoid these issues entirely by giving your team the information they need to work safely and efficiently.

What 811 Doesn't Find

One of the biggest misconceptions in our industry is that calling 811 gets all your utilities marked. The truth is, the free 811 service only locates public utilities, which are the lines owned and maintained by utility companies up to your meter. Everything on the other side of that meter, running across your property, is considered private. This includes power lines to outbuildings, water lines for irrigation, sewer laterals, and communication cables between buildings.

These private lines are your responsibility, and 811 won't find them for you. This is the critical gap where most utility strikes happen. A private utility locating service is designed specifically to fill this gap. We use specialized equipment to trace all the private infrastructure on your site, giving you a complete and accurate map. Calling 811 is a good first step, but it’s not the final one.

How Does Subsurface Locating Technology Work?

So, how do we actually see what's buried beneath your job site? It’s not a single magic wand, but a combination of sophisticated technologies that work together. Think of it like a doctor using different diagnostic tools to get a full picture of a patient's health. A professional locator uses multiple methods to create a reliable map of everything hidden underground, from water lines to fiber optic cables. This comprehensive approach is what allows us to deliver accurate subsurface utility mapping that you can confidently use for planning your excavation, trenching, or boring.

The three core technologies in our toolkit are Ground Penetrating Radar (GPR), Electromagnetic (EM) locating, and passive detection. Each one excels at finding different types of targets and works best under specific conditions. By layering the data from each method, we can cross-reference findings, confirm the location of known utilities, and uncover unexpected obstacles that a single-technology approach would miss. Understanding how these tools work will give you a better sense of what’s possible and why a professional, multi-faceted locate is so critical for project safety and efficiency.

Ground Penetrating Radar (GPR)

Ground Penetrating Radar, or GPR, is one of the most versatile tools we have. It works by sending high-frequency radio waves into the ground. When these waves hit an object, like a pipe or a void, they bounce back to a receiver. The system then translates that data into a real-time image on a screen, showing us a cross-section of what’s below. The biggest advantage of GPR is its ability to find almost anything, including non-metallic lines like PVC, concrete, and fiber optics that other tools miss. It’s also effective in various ground conditions, from soil and clay to asphalt and concrete, making it essential for our utility locating services.

Electromagnetic (EM) Locating

Electromagnetic (EM) locating is the go-to method for finding conductive metal pipes and cables. The equipment consists of a transmitter and a receiver. The transmitter sends a specific frequency through the ground, which creates an electromagnetic field around a metallic line. The receiver then detects this field, allowing us to trace the line’s path with incredible accuracy. While it’s perfect for locating metal, its main limitation is that it cannot detect non-conductive materials. This is why we never rely on EM alone. An EM locator might identify a gas line, but a follow-up GPR scan is needed to confirm its depth and check for a nearby plastic water line that the EM tool would have missed completely.

Passive Detection

Passive detection is a more subtle but equally important technique. Instead of sending out a signal, this method involves "listening" for the electromagnetic fields that are already being emitted by live, active utilities. Think of live electrical cables or certain types of communication lines. These utilities generate their own detectable signals just by being in use. We use a specialized receiver to pick up on these ambient fields, which helps us confirm the presence and location of active lines. It’s an excellent way to verify findings from GPR and EM scans and adds another layer of confidence that we’ve identified all active utilities on your site before you start digging.

811 vs. Private Locating: What's the Difference?

One of the biggest misconceptions in excavation is that a call to 811 is all you need to do before breaking ground. While it’s a critical first step, it’s not the complete picture. The 811 service and private locating are two different services that work together to ensure site safety. Understanding the role of each is the key to preventing dangerous utility strikes, costly project delays, and unexpected repairs. Think of it as a two-part process for total subsurface awareness. The public service gives you one piece of the puzzle, and a private firm provides the rest. Let's break down what each service covers and how to use them effectively.

The Limits of the Public 811 Service

Calling 811 is a free, legally required step before any digging project. When you make the call, public utility companies are notified to come out and mark the lines they own and operate on your property. This typically includes main lines for gas, water, electricity, and telecommunications that run from the street to your meter. The problem is, their responsibility ends at the meter. Any utility lines that run from the meter to a building, or between buildings on your property, are considered private. This means the power line to a security gate, the water line for an irrigation system, or the fiber optic cable connecting two offices won't be marked by 811, leaving you with dangerous blind spots.

The Advantages of a Private Locate

This is where a private locating service comes in. A private locator’s job is to find the utilities that 811 doesn’t cover. Using advanced tools like Ground Penetrating Radar (GPR) and Electromagnetic (EM) locators, technicians can scan your entire project area to identify all buried infrastructure. This includes metallic and non-metallic pipes, electrical conduits, and communication cables. Beyond just finding lines, a private firm provides a much higher level of detail. You get a comprehensive map of your site, often with depth estimates, which is essential for planning safe excavation paths. This subsurface utility mapping gives you the confidence that you know what’s below before you start work.

When to Use Both Services

The safest approach isn’t choosing one service over the other; it’s using both. Think of it as a sequence. Your first call should always be to 811 to get the public utilities marked. Once those flags and paint are on the ground, you have your baseline. The next step is to hire a private locating firm to fill in the gaps. A private crew will scan the areas inside and around the public marks to find everything else. This two-step process ensures you have a complete and accurate map of all buried hazards. By layering the free public data with detailed private data, you practice the highest level of due diligence and drastically reduce your risk of a costly and dangerous utility strike.

What Can Subsurface Locating Find?

When you call for a private locate, you’re getting a much more detailed picture of what’s happening beneath your job site. Unlike the public 811 service, which only marks member utility lines up to the meter, a private scan investigates everything within your project area. The goal is to create a complete map that accounts for both known utilities and unexpected obstacles, so you can dig with confidence. This includes everything from primary power and communication lines to secondary water lines running to an irrigation system or a fire hydrant.

Using a combination of technologies gives us the flexibility to identify a wide range of targets. While one method might be perfect for finding a metal pipe, it could completely miss a plastic conduit right next to it. That’s why a thorough investigation relies on having the right tools for the job and experienced technicians who know how to interpret the data. We can find metallic and non-metallic pipes, electrical conduits, fiber optic cables, and even unmarked structures like old foundations or abandoned tanks. From active power lines to old, forgotten structures, a comprehensive locate helps ensure you don’t run into expensive and dangerous surprises.

Metallic Pipes and Conduits

Metallic lines, like copper, steel, and iron pipes, are typically the most straightforward targets to locate. Using an electromagnetic (EM) locator, a technician can apply a current to the line and trace its signal path across your site. This method is highly effective for active, conductive utilities.

But what happens if a line is old, disconnected, or has a broken tracer wire? In these cases, an EM locator won't work. This is where Ground Penetrating Radar (GPR) becomes essential. GPR sends radio waves into the ground and reads the returning signals to detect objects. It can easily find underground pipes made of metal without needing a conductive signal, making it the perfect backup for confirming the location of questionable or un-energized metallic utilities.

Non-Metallic Lines (PVC, Fiber Optics)

Modern construction relies heavily on non-metallic materials like PVC for water and sewer lines, and of course, fiber optic cables for communications. These materials are a major blind spot for standard EM locators. Since they don't conduct electricity, an EM wand will pass right over them as if they aren’t there. This is one of the most common reasons for costly utility strikes.

To find these "un-locatable" lines, GPR is the only reliable solution. Because GPR detects changes in subsurface materials, it can identify plastic pipes and fiber conduits just as effectively as metallic ones. Our crews use GPR to scan for these non-conductive targets, ensuring our utility locating services provide a complete and accurate picture of everything buried on your site.

Unknowns and Deeply Buried Targets

Sometimes the biggest risks aren't on any blueprint. Over the years, a property can accumulate all sorts of buried debris, including old foundations, abandoned septic tanks, forgotten drainage systems, and underground storage tanks (USTs). Hitting one of these with an excavator can stop a project in its tracks.

A comprehensive site scan is designed to uncover these unknowns. By combining GPR, EM, and other passive detection methods, technicians can identify anomalies that don't match known utility paths. This process helps build a complete subsurface utility map that accounts for both active utilities and buried structures. This is especially important for environmental assessments or when redeveloping older properties where historical records are incomplete or non-existent.

Common Myths About Utility Locating

When it comes to digging, what you don’t know can definitely hurt you. Misunderstandings about utility locating are common, and they can lead to dangerous and expensive mistakes. Let’s clear up a few of the most persistent myths so you can plan your next project with confidence and keep your crew safe.

Myth: "811 marks everything on my property."

This is easily the biggest misconception in the industry. The public 811 service is an essential first step, but it has clear limits. Public locators are only responsible for marking the utility lines that their member companies own, and they stop at the meter or service tie-in. Any lines running from the meter to your main building, or between buildings on a large property, are considered private. This includes power for outdoor lighting, water lines for irrigation, or fiber optic cables connecting different facilities. To find these, you need a dedicated private utility locating service that can map out the entire site.

Myth: "Any locating service will do."

Not all locating services are created equal. The free 811 service typically uses one primary method to find public lines. A professional private locate is a much more comprehensive process. Experienced technicians use multiple technologies, like Ground Penetrating Radar (GPR) and Electromagnetic (EM) locators, to get a complete picture of the subsurface. This combination of tools is what allows them to find non-metallic pipes, abandoned lines, and other unknowns that a basic locate would miss. True subsurface utility mapping requires specialized equipment and the expertise to interpret the data correctly, ensuring you have an accurate map before breaking ground.

Myth: "It's too expensive for my project."

Thinking of a private locate as just another expense is a mistake. It’s an investment in risk management. The cost of a professional locate is minimal when you compare it to the potential costs of a utility strike. Hitting a single line can lead to thousands of dollars in repairs, significant project delays, hefty fines, and, most importantly, a serious risk of injury to your team. A private locate provides the certainty you need to work efficiently and safely. By identifying potential conflicts ahead of time, you prevent budget overruns and keep your project on schedule, saving you far more money than the initial cost of the scan.

What Determines the Cost of a Private Locate?

One of the first questions we get is, "How much will this cost?" It's a fair question, but the answer isn't a single number. The cost of a private locate is an investment in your project's safety and timeline, preventing costly strikes and delays down the road. Think of it less as an expense and more as insurance against hitting a fiber line or a gas pipe. Because every site is different, a one-size-fits-all price just doesn't exist in this line of work. A reputable company will always want to understand your project's specifics before giving you a number.

While every project is unique, the price for a private utility locate generally comes down to three key factors: the size and complexity of your work area, the technology needed to find everything, and the type of report you need when the fieldwork is done. Understanding these elements will help you get a clear and accurate quote for your specific job. It also helps you see exactly what you're paying for, which is peace of mind and clean, actionable data for your team. We can provide a much more precise estimate once we know a little more about your site and what you’re trying to accomplish.

The Size and Complexity of Your Site

The most straightforward factor is the size of the area you need to be scanned. A small trench path for a new fiber optic line will naturally take less time and resources than scanning a multi-acre commercial lot for a new build. But it’s not just about square footage. The complexity of the site plays a huge role. An open, grassy field is much simpler to work on than a congested industrial facility with dense rebar, multiple layers of pavement, and years of undocumented utility installations. The more complex the environment, the more time our technicians need to carefully investigate the area and accurately distinguish between different subsurface targets.

The Technology Required

Not all utilities are created equal, and neither are the tools used to find them. The cost can shift based on the specific technologies needed for your site. Simple metallic pipes can often be found with standard electromagnetic (EM) equipment. However, if your project involves finding non-conductive lines like PVC, concrete pipes, or fiber optics, we’ll need to use Ground Penetrating Radar (GPR). Often, the best and most reliable results come from using a combination of methods. Our expert crews determine the right tools for the job, ensuring we find everything without wasting time on methods that won’t work for your specific site conditions and utility types.

The Final Report and Deliverables

What do you need once the lines are found? The answer affects the final cost. For some projects, simple paint marks on the ground are enough to guide an excavator for a quick dig. This is the most basic deliverable. Other projects, especially those involving long-term planning or engineering design, require more detailed documentation. You might need a simple field sketch showing the locations of the marked utilities. For the highest level of accuracy and future use, we can provide a detailed GPS and GIS map that overlays the utility data onto your site plans. The more comprehensive the final report, the more value it provides for future work.

What Affects Locating Accuracy?

Getting a clear picture of the underground isn't always straightforward. Even with the best technology, accuracy depends on what’s happening below the surface. Think of it like trying to have a conversation in a noisy room; sometimes, you have to work a little harder to hear what’s being said. The same is true for subsurface locating. The signals from our equipment can be distorted or weakened by a few key factors.

An experienced technician understands these challenges and knows how to interpret the data despite them. It’s not just about running a machine over the ground; it’s about understanding the science behind the signals and how the environment affects them. The three biggest variables we contend with on any job site are the ground itself, the type of utility we’re looking for, and how deep it’s buried. Each one presents a unique puzzle, which is why a one-size-fits-all approach rarely works. A professional locate combines the right tools with the expertise to read the results accurately, giving you a reliable map to work from.

Challenging Soil and Site Conditions

The ground you’re standing on plays a huge role in locating accuracy. Different soil types interact with GPR and EM signals in different ways. For example, dense, wet clay can absorb GPR signals, making it difficult to see what’s underneath. Sandy or loamy soils are much easier to scan. Rocky terrain can also create false positives, reflecting signals in unpredictable ways. Beyond the soil, the surface conditions matter too. A site cluttered with buildings, vehicles, or reinforced concrete can create significant electromagnetic interference, making it harder to isolate the signals from the utilities you need to find. An expert knows how to adjust their equipment and approach to account for these unique site conditions.

Utility Material and Signal Interference

Not all utilities are created equal. Metallic pipes and conduits are often the easiest to find because they conduct an electromagnetic signal well. We can induce a current onto the line and trace it directly. However, non-metallic lines like PVC, asbestos cement, and fiber optic cables don't conduct electricity. For these, we rely on Ground Penetrating Radar (GPR) to detect them. This is why using a mix of technologies is so important. Relying on just one method means you’ll likely miss something. Signal interference from other sources, like overhead power lines or adjacent utilities, can also make it tough to get a clean reading on your target line.

The Depth of the Target

As a general rule, the deeper a utility is buried, the harder it is to detect. The signal from any locating device, whether it's GPR or EM, gets weaker as it travels deeper into the ground and back to the receiver. At a certain point, the signal becomes too faint to be reliable. Professional-grade equipment has more power and sensitivity to find these deeper targets, but there are still physical limits. This is a key reason why you need a private utility locating service for major projects. We have the tools and experience to identify deeply buried infrastructure that might not show up with standard equipment or during a basic survey.

What to Expect During a Private Locate

When you hire a private locating team, you’re investing in certainty. The process is designed to give you a clear and accurate picture of what’s happening beneath your site. From the initial planning session to the final report, every step is focused on delivering actionable data you can trust for your excavation, boring, or design work. Here’s a breakdown of what the process looks like.

The Initial Site Walk and Plan

The process begins with a conversation. Your locating technician will start with a site walk to understand the project's scope and goals. This is your chance to share any existing site plans or historical knowledge about the property. A qualified private utility locating service specializes in finding what public services miss, so defining the search area is a critical first step. We’ll discuss the known utilities, identify potential challenges, and create a clear plan of action before any equipment is turned on. This initial collaboration ensures the fieldwork is as efficient as possible.

Fieldwork: Scanning and Marking

Once the plan is set, our field crew gets to work. Using a combination of technologies is key to getting a complete picture. We use tools like Ground Penetrating Radar (GPR) to detect non-metallic lines and Electromagnetic (EM) locators to trace metallic pipes. As we identify subsurface utilities, we mark their location on the surface with paint and flags, following the standardized APWA color code. Site conditions can influence the process, but an experienced technician knows how to interpret the data and adjust their methods to ensure the most accurate results.

Your Final Map and Report

The on-site markings are just one part of the final deliverable. The real value comes from the comprehensive report that synthesizes all the field data into a clear, usable format. Depending on your project's needs, this could be a detailed field sketch or a precise digital map. For complex projects, we provide engineer-ready data overlays, including GPS and GIS mapping that integrates into your design files. This final report is your permanent record of the subsurface conditions, giving your team the confidence to dig safely without hitting unexpected and costly obstacles.

When Should You Call for a Private Locate?

Knowing when to call for a private locate is just as critical as knowing who to call. While the public 811 service is a mandatory first step, it’s not a complete solution. A private utility locator steps in to fill the gaps, giving you a full picture of the subsurface environment. Getting your timing right protects your project, your budget, and your crew. If you’re managing a site, certain scenarios should always trigger a call to a private locating expert.

Before Any Excavation or Construction

Any time you plan to break ground, you should schedule a private locate after you’ve completed your 811 call. This includes everything from trenching for new fiber optic lines and planning soil borings to grading a site for a new foundation. Public services only mark utility-owned lines up to the meter. Everything beyond that point, like power lines running to a parking lot light or a water line to an irrigation system, is considered private and won't be marked.

Only a qualified private utility locating service has the equipment and expertise to find these hidden lines. While it might feel like an extra step, investing in a private scan is a smart financial decision. The cost of a thorough locate is minimal compared to the thousands of dollars in repairs, downtime, and potential fines that come from striking an unmarked utility.

For Environmental Site Assessments

Private locating is essential for environmental due diligence, especially during Phase I and Phase II Environmental Site Assessments (ESAs). Before a property is purchased or redeveloped, consultants need to identify potential environmental liabilities hiding underground. This is particularly important for former industrial sites, gas stations, or commercial properties where undocumented infrastructure could exist.

Using technologies like Ground Penetrating Radar, technicians can perform tasks like subsurface tank locating to determine if old fuel tanks were left behind. Locators can also identify abandoned pipes, septic systems, and other buried structures that could pose a contamination risk. This data provides a clear record of what’s below the surface, protecting buyers from unexpected cleanup costs and legal issues down the road.

Planning New Utility Installations

When you’re designing a new project, you need to know where you can safely and efficiently install new infrastructure. A private locate provides the comprehensive data needed to plan new utility routes without conflicts. As project complexity increases, so does the need for sophisticated detection methods to create a reliable map of the existing subsurface environment.

Whether you're adding electrical conduits, gas lines, or communication cables, knowing the precise location of all buried utilities is key. This allows engineers and architects to design around obstacles, preventing costly and time-consuming redesigns during construction. With accurate data, you get clean, engineer-ready results that make the entire installation process smoother, faster, and safer for everyone involved.

How to Choose the Right Locating Partner

Finding the right partner to map your site’s underground infrastructure is one of the most important decisions you’ll make before breaking ground. The quality of your locate directly impacts project safety, timelines, and your budget. While many companies offer locating services, their expertise, equipment, and the clarity of their results can vary dramatically. To protect your project from costly strikes and delays, you need a partner who delivers on all three fronts. When you’re vetting a private locating company, focus on these key areas to ensure you’re working with a team that can truly find what 811 misses and give you data you can build on.

Experienced Technicians, Not Call Centers

When you have a question about a mark on the ground, the last thing you want is to be routed through a call center. You need to speak with the person who was actually on-site. A great locating partner gives you direct access to their field experts. These technicians aren't just following a manual; they’re using years of experience to interpret complex signals and make critical judgments in real time. A qualified private utility locating service employs technicians who understand the nuances of different soil conditions and can adapt their methods on the fly. They know how to solve problems in the field, ensuring you get a complete and accurate picture of what’s below.

The Right Tools for the Job

Effective utility locating is rarely a one-tool job. A reliable partner arrives with a full suite of technology, because different targets require different methods. While an electromagnetic (EM) locator is great for finding conductive pipes and cables, it can’t find non-metallic lines like PVC or fiber optics. That’s where Ground Penetrating Radar (GPR) comes in. A professional crew knows how to use these technologies together to create a comprehensive map. They’ll assess your site’s specific challenges and select the right equipment to get the job done, rather than relying on a single, limited approach. This tailored strategy is essential for achieving accurate subsurface utility mapping.

Clear, Actionable Results

The final deliverable is what you’re paying for, so it needs to be clear, accurate, and immediately useful. A successful locate ends with more than just a few flags in the ground. Your partner should provide results you can act on with confidence. This means clean, easy-to-read paint marks in the field and, for more complex projects, a detailed digital map that your engineers and excavation crews can use for planning. A trustworthy company is transparent about what their final report includes and how the data is presented. You should never be left guessing what a line on a map means or where a utility is actually buried.

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Frequently Asked Questions

I already called 811. Do I still need a private locate? Calling 811 is the right first step, and it's required by law. However, the 811 service only marks public utilities, which are the lines owned by utility companies up to your meter. A private locate is the second step that covers everything else. This includes all the lines on your side of the meter, like power to a security gate, water lines for an irrigation system, or fiber optic cables connecting buildings on a campus. These private lines are your responsibility, and a private locate is the only way to find them before you dig.

Is a private locate worth the cost? Think of a private locate as an investment in risk management rather than just another project expense. The cost of a professional scan is a small fraction of what you would pay to repair a single utility strike. Hitting a fiber line can cause thousands of dollars in damage and downtime, not to mention the project delays and potential fines. By identifying all buried hazards before work begins, you prevent these costly surprises, keep your crew safe, and ensure your project stays on schedule and on budget.

Can you really find plastic pipes and fiber optic cables? Yes, absolutely. This is a perfect example of why using the right technology matters. Standard locating tools that rely on electromagnetic signals can only find metallic lines. They are completely blind to non-conductive materials like PVC pipes, concrete conduits, and fiber optic cables. We use Ground Penetrating Radar (GPR), which sends radio waves into the ground to identify changes in the subsurface. This allows us to see those "un-locatable" lines and give you a complete map of your site.

How accurate are the markings? The accuracy of a locate depends on a few factors, including soil conditions, the depth of the utility, and any on-site interference. For example, dense clay or reinforced concrete can make signals harder to read. This is precisely why experience matters. A skilled technician knows how to interpret the data from multiple technologies, like GPR and EM locators, to account for these challenges. They can cross-reference signals and use their expertise to provide the most precise markings possible for your specific site conditions.

What do I get after the locate is finished? Our goal is to give you clear, actionable results you can use immediately. At a minimum, you will see paint marks and flags on the ground that show the horizontal location of the utilities we find. For projects that require more documentation, we can create a simple field sketch or a detailed digital map. We can even provide engineer-ready GPS or GIS data that overlays the utility locations directly onto your design plans, giving you a permanent and precise record for any future work.