Level A B C D SUE Explained: A Simple Guide

Think of mapping underground utilities like creating a portrait. You can start with a rough pencil sketch based on old descriptions, which gives you a general idea of the subject. That’s the first step. Then, you can go outside and add details based on what you can see, refining the outline. Next, you can use advanced tools to trace the exact shape and position, bringing the image into focus. Finally, you can add color and texture by observing the subject up close, capturing every detail with perfect accuracy. This is exactly how SUE works. Having Level A B C D SUE explained shows you how we build from a simple records search to a precise, visually confirmed location, giving you a progressively clearer picture of the subsurface.

Key Takeaways

• Understand the SUE Quality Levels: This standardized framework, from Level D (records) to Level A (visual proof), lets you classify the reliability of utility data so you know exactly what you're working with before breaking ground.
• Choose the right tool for the job: You don't always need the highest level of investigation. Match the SUE Quality Level to your project's specific risks and budget to get the data you need without overspending.
• Invest in data to avoid disaster: A professional SUE investigation is an upfront investment in certainty that provides the reliable data needed to prevent costly utility strikes, avoid project delays, and keep your team safe.

What is Subsurface Utility Engineering (SUE)?

Think of Subsurface Utility Engineering (SUE) as a professional process for mapping the underground. It’s a systematic approach to identifying, characterizing, and documenting the utilities buried beneath a project site. While calling 811 is a necessary first step for locating public utilities, it doesn't cover private lines or provide the detailed data needed for complex engineering and construction projects. SUE fills that gap by creating a comprehensive and reliable picture of what’s really down there.

This isn't just about waving a wand over the ground. SUE is an engineering practice that combines geophysics, surveying, and data management to reduce uncertainty. By using advanced tools and a standardized methodology, SUE provides engineers, contractors, and site owners with the critical information needed to plan, design, and build safely. It’s the difference between guessing where a fiber line is and knowing its exact horizontal and vertical position. This level of detail is essential for preventing costly utility strikes, avoiding project delays, and making informed decisions before the first shovel ever hits the dirt. At its core, SUE is about managing the risks you can't see.

What SUE Aims to Achieve

The main goal of SUE is to give project managers reliable data so they can make smart decisions early in the design process. Instead of discovering a conflict with a water main during excavation, SUE identifies that risk beforehand. This allows designers to adjust plans or schedule utility relocations before construction begins, preventing expensive surprises and dangerous accidents.

Ultimately, SUE moves projects from a reactive to a proactive approach. It provides a clear, verified understanding of subsurface conditions, which helps streamline coordination between teams and reduces the potential for change orders and downtime. The purpose isn't just to find utilities; it's to deliver quality data that supports safer, more efficient project execution from start to finish.

The Standards That Guide SUE

SUE isn't an informal process; it’s guided by a national standard that ensures consistency and reliability. The primary framework is the ASCE/UESI 38-22 standard, which outlines a clear methodology for collecting and presenting subsurface utility data. This standard defines four distinct Quality Levels (QLs), ranging from D (the least certain) to A (the most certain).

Following these guidelines is what separates professional SUE from a simple utility locate. Each quality level has specific requirements for how data is gathered and verified, giving you a clear understanding of the accuracy you're getting. This standardized approach ensures that everyone on the project team—from engineers to excavators—is working from the same playbook, with a shared understanding of the data's reliability.

Is SUE Worth the Investment?

Absolutely. Investing in SUE at the beginning of a project consistently saves money and time down the line. The data speaks for itself: a landmark study by the Federal Highway Administration found that for every $1.00 spent on SUE, projects saved an average of $4.62. These savings come from avoiding utility strikes, minimizing costly project redesigns, and preventing unexpected delays.

When your team has accurate utility data, they can make informed decisions throughout the entire design and construction process. This reduces the need for last-minute changes and improves overall project coordination. By investing in a clear understanding of your site's subsurface conditions, you’re not just buying data—you’re buying certainty and protecting your project's budget and timeline.

What Are the SUE Quality Levels?

When you’re planning an excavation, the last thing you want is a surprise. Subsurface Utility Engineering (SUE) provides a standardized framework to manage that risk by classifying the quality of utility data. Think of it as a grading system for how much you can trust the information about what’s buried underground. The American Society of Civil Engineers (ASCE) established four quality levels, ranging from D (the least reliable) to A (the most reliable).

This system isn’t about getting an "A" on every project. Instead, it’s a practical tool that helps you match the quality of the data to the level of risk. For a simple landscaping project far from any known utilities, lower-quality data might be fine. But if you’re planning to drill soil borings or trench next to a critical fiber optic line, you’ll need the highest level of certainty. Understanding these levels helps you make informed decisions, prevent costly utility strikes, and keep your project on schedule. Each level builds on the one before it, creating a progressively clearer picture of the subsurface.

Quality Level D: Starting with Existing Records

Quality Level D is the starting point for any SUE investigation. This phase is all about gathering and reviewing existing records. We’re talking about utility maps, as-built drawings, old site plans, and even interviews with facility staff who have historical knowledge of the area. It’s essentially a records search to get a general idea of which utilities might be present.

While it’s a necessary first step, Level D data comes with a big disclaimer: it can be incomplete, outdated, or just plain wrong. Records may not reflect repairs or relocations, and memories can be unreliable. This level gives you a preliminary look, but it doesn't provide enough confidence for design or excavation.

Quality Level C: Surveying What You Can See

Quality Level C takes the desk research from Level D and brings it into the field. This step involves a visual survey to map all visible, above-ground utility features. A survey crew will locate and record the position of manholes, valve boxes, utility poles, fire hydrants, and communication pedestals.

This information is then correlated with the existing records from Level D. Often, this is where discrepancies start to appear—a manhole is in a different spot than the drawing shows, or a valve isn't on the map at all. Level C adds a layer of verification by confirming what’s visible on the surface, but it still doesn’t tell you anything definitive about the location of the buried lines between those features.

Quality Level B: Detecting Utilities from the Surface

This is where we move from reviewing records to actively searching for buried utilities. Quality Level B involves using geophysical instruments to detect utilities from the surface. Technicians use tools like Ground Penetrating Radar (GPR) and electromagnetic (EM) locators to trace the approximate horizontal alignment of underground lines. The findings are then marked on the ground with paint or flags.

This is a huge leap in accuracy from Levels D and C. Our private utility locating services operate at this level to provide a clear map of what’s underground. While Level B is highly effective for determining the horizontal position of a utility, it typically doesn't provide precise vertical information, or depth.

Quality Level A: Confirming with Visual Proof

Quality Level A is the highest and most accurate level of utility data available. It’s often called "daylighting" or "potholing" because it involves physically exposing the utility to confirm its exact location. This is typically done using non-destructive vacuum excavation to create a small test hole, allowing for direct visual confirmation.

Once exposed, the utility's precise horizontal and vertical position, size, material, and condition can be measured and recorded. This level of certainty is essential in high-risk areas, such as when designing new infrastructure that will cross or run parallel to existing critical utilities. It removes all ambiguity and provides the ground-truth data needed for final design and construction.

How Accuracy Improves with Each Level

The SUE quality levels are designed to work together as a progressive system. You don’t just pick one; you build upon them to create a comprehensive understanding of the subsurface. The process starts with the broad overview from Level D records, gets refined with the visual survey in Level C, and becomes much clearer with the geophysical investigation in Level B. Finally, Level A is used strategically at critical points where absolute certainty is required.

This phased approach allows you to manage risk and cost effectively. You can apply a broad Level B investigation across your entire project site and then use targeted Level A test holes only at points of potential conflict. This integrated process is the foundation of a reliable subsurface utility mapping effort, ensuring you have the right data quality for the right job.

The Tools and Tech Behind Each Quality Level

Each SUE quality level corresponds to a specific set of actions and tools. As you move from Level D to Level A, the methods become more hands-on and the technology gets more advanced, delivering progressively more reliable data. Think of it as moving from a rough sketch to a high-resolution photograph of your site’s subsurface. This process ensures that every piece of information is backed by a clear, traceable method, giving you a complete picture of what lies beneath the surface and how certain that information is. Understanding the tools used at each stage helps you appreciate the value and limitations of the data you receive, allowing you to make smarter, safer decisions for your project.

Gathering Existing Utility Data

Quality Level D is all about detective work. The main tools here aren't physical; they're records and institutional knowledge. We start by collecting and reviewing as-built drawings, utility maps, old surveys, and any other existing documentation related to the site. This step also involves interviewing facility managers, maintenance staff, or anyone with long-term knowledge of the property. While this information provides a general idea of what utilities might be present, it’s often outdated, incomplete, or inaccurate. It’s the essential first step that creates a baseline understanding, but it’s never trusted on its own for design or excavation.

Mapping Visible Surface Features

For Quality Level C, we take the information from our records review and head out to the field. The primary tools are professional surveying instruments, including GPS and GIS equipment. Our crew surveys and maps all visible, above-ground utility features, such as manholes, valve boxes, fire hydrants, and utility risers. We then correlate this physical evidence with the records gathered in Level D. This step helps confirm or contradict the old maps and provides a more accurate horizontal position for the utilities we can see. This process of GPS & GIS mapping connects the dots between the paper plans and the physical reality of your site.

Using GPR and Electromagnetic Locators

This is where advanced technology comes into play for Quality Level B. We use a combination of geophysical instruments to detect utilities from the surface. The two workhorses are Ground Penetrating Radar (GPR) and Electromagnetic (EM) locators. GPR sends radio waves into the ground and reads the reflections to identify both metallic and non-metallic pipes and conduits. EM locators work by detecting the electromagnetic field around conductive utilities. By using these tools, our utility locating services can determine the approximate horizontal position of buried lines, which are then marked on the ground with paint or flags.

Pinpointing Exact Utility Locations

Quality Level A provides the highest degree of accuracy because it involves visual confirmation. The main technique is non-destructive digging, often called "potholing" or "daylighting." Using a vacuum or hydro-excavator, we carefully create small test holes to physically expose the target utility. This allows us to see the line with our own eyes and collect precise measurements of its horizontal and vertical position, as well as its size and material type. This is the only way to be absolutely certain of a utility's location, making it the gold standard for critical design and pre-excavation checks where conflicts are anticipated.

Bringing All the Data Together

The final step is to synthesize all the information into a single, comprehensive deliverable. Using the data from every quality level, we create a detailed map of your site’s subsurface. On this map, each utility is clearly labeled with the SUE quality level used to locate it. This is a critical feature of professional subsurface utility mapping. It allows engineers, designers, and project managers to immediately understand the reliability of the data for each line. A utility marked "QL-B" is a reliable approximation, while one marked "QL-A" is a confirmed fact, giving your team the confidence to design and dig safely.

How to Choose the Right SUE Quality Level

Picking the right SUE Quality Level isn’t about always aiming for Level A. It’s about making a smart, strategic choice that aligns with your project’s specific goals, risks, and budget. Think of it like a diagnostic tool—you wouldn’t order an MRI for a scraped knee. Similarly, you don’t always need to pay for vacuum excavation when existing records might suffice for preliminary planning. The key is to match the level of investigation to the level of risk you’re willing to accept.

Making the right choice from the start saves you from two major headaches: overspending on unnecessary data or, far worse, underspending and facing a catastrophic utility strike that derails your entire project. A thoughtful approach ensures you get exactly the data you need to move forward with confidence. By weighing a few key factors, you can pinpoint the quality level that provides the perfect balance of accuracy, cost-effectiveness, and safety for your job site. This decision is fundamental to a successful project, as Subsurface Utility Engineering is applied during the design phase to locate, identify, and characterize all existing utility infrastructure.

Define Your Project's Needs

First, get clear on what you’re trying to accomplish. The SUE level you need depends entirely on your project's phase and scope. Are you in the early stages of feasibility planning and just need a rough idea of what’s underground? Quality Level D, which relies on existing records, might be enough. But if you’re creating detailed engineering plans for a major excavation, you’ll need the much higher certainty of Level B or A. The goal is to gather enough information to make critical design decisions without exposing your project to unnecessary risk. Match the data quality to the decisions you need to make at each stage.

Assess Your Project's Risk

Every excavation carries risk, but not all risks are equal. Digging a shallow trench in an open field is very different from drilling boreholes next to a hospital’s critical power and data lines. Consider the density of utilities in your project area and the potential consequences of a strike. A damaged water line is a problem; a severed fiber optic cable can be a crisis. Higher-risk projects demand higher SUE quality levels because quality utility data supports informed decision-making and reduces conflicts. By investing in more accurate data upfront, you are actively managing your project’s exposure to costly damages, delays, and safety hazards.

Factor in Your Budget

While budget is always a consideration, it’s crucial to view SUE as an investment in risk mitigation, not just an expense. The cost of a utility strike—including repairs, downtime, and potential fines—almost always dwarfs the cost of a thorough SUE investigation. While Level A is the most intensive and costly upfront, it provides certainty that can prevent a six-figure accident. The key is to find the sweet spot where you’re not overpaying for data you don’t need but are investing enough to protect your project. As experts note, while cost savings are critical, risk mitigation is just as important on any project.

Consider the Site Conditions

The physical characteristics of your site play a big role in choosing a SUE level. A project in a new development with well-documented utilities is much simpler than one in a historic urban core where records are incomplete or nonexistent. Start by looking at what’s visible. Quality Level C enhances investigations by systematically surveying visible utility features like manholes, valves, and utility poles. If you see a lot of surface features but have poor records, it’s a clear sign you need to advance to Level B to electronically sweep the area and verify what’s actually hidden below.

Check for Regulatory Rules

Finally, make sure you’re following the rules. Many public agencies, especially departments of transportation, have specific requirements for SUE on their projects. These mandates are in place to ensure safety and protect public infrastructure. The primary guide for this work is the ASCE 38-22 standard, which outlines the definitions and procedures for each quality level. Before starting your project, confirm if any local, state, or federal regulations dictate a minimum SUE level. Adhering to these standards isn’t just about compliance—it’s about adopting a proven framework for reducing risk.

Ensuring Quality in Your SUE Project

A successful Subsurface Utility Engineering (SUE) project is more than just a final map. It’s the result of a deliberate, quality-driven process that starts long before the first GPR unit is rolled out. When you prioritize quality at every step, you’re not just getting a more accurate picture of the underground; you’re actively preventing costly utility strikes, redesigns, and project delays. A commitment to quality means your team can make decisions with confidence, knowing the data they’re working with is reliable and verified.

This process doesn’t happen by accident. It requires clear standards, consistent verification, and seamless coordination between everyone involved. From the initial records search to the final deliverable, every action contributes to the integrity of the data. By implementing a few key practices, you can ensure your SUE project delivers the clear, actionable results your team needs to dig safely and build efficiently. It’s about building a framework for success that protects your people, your budget, and your timeline.

Set Clear Data Collection Standards

To get consistent results, you need to start with clear expectations. Setting data collection standards means defining exactly what information needs to be gathered and how it should be recorded. This ensures that everyone, from the field technicians to the project managers, is working from the same playbook. When your SUE provider establishes these standards early, the data collected is uniform and reliable, making it easier to integrate into your design plans. This simple step removes ambiguity and helps maintain data quality across the entire project, giving your team the solid foundation it needs for informed decision-making.

Establish How You'll Verify Findings

Trust, but verify. This is especially true when you’re dealing with buried utilities. A crucial part of any quality SUE process is establishing how findings will be confirmed. While technologies like GPR and EM locators are incredibly powerful, the most certain method is visual confirmation. This is the core of Quality Level A data, which involves physically exposing a utility through methods like vacuum excavation to confirm its exact horizontal and vertical position. By planning for verification, especially in high-risk areas, you eliminate guesswork and build a higher level of confidence into your project plans.

Keep Detailed, Accurate Records

Great data is useless if it isn’t documented properly. Keeping detailed and accurate records is fundamental to a quality SUE project. This goes beyond the final map and includes field notes, photographs, equipment calibration logs, and sketches. According to the Common Ground Alliance, the goal is to locate, identify, and characterize utilities. Thorough documentation is what allows for that deep characterization, providing context that a simple line on a map can’t. These records create a clear audit trail and become an invaluable resource for future work on the site.

Coordinate Your Field and Office Teams

The best SUE outcomes happen when there’s a strong connection between the crew in the field and the team in the office. Field technicians are the ones gathering the raw data and observing site conditions firsthand, while the office team processes that data into engineer-ready deliverables. Constant and clear communication ensures that what’s seen on the ground is accurately reflected in the final plans. When SUE providers work collaboratively with design teams and utility owners, potential issues are identified and resolved quickly, preventing misunderstandings that could lead to errors down the line.

Integrate Your Tech and Tools

Modern SUE relies on a suite of advanced tools, and quality depends on using them together effectively. It’s not about having one piece of technology; it’s about integrating multiple technologies to create a comprehensive view. For example, combining GPR data with EM locator findings helps confirm the presence of both metallic and non-metallic lines. When this field data is tied to precise GPS coordinates, you get a complete and accurate subsurface utility map. Following industry standards like ASCE 38-22 ensures that this technology is applied systematically, turning raw signals into reliable, actionable intelligence for your project.

Frequently Asked Questions

How is SUE different from the free 811 service? Think of 811 as the first, mandatory step and SUE as the complete, professional follow-through. The 811 service is essential for locating public utilities running up to your property line, but that’s where their responsibility ends. SUE is a comprehensive engineering process that maps everything else, including the private water, gas, and fiber lines that 811 doesn’t cover. It provides a much higher level of detail and a verifiable quality rating for the data, giving your engineers the reliable information they need for safe and efficient design.

Do I need to get a Quality Level A investigation for my entire site? Not at all, and that’s one of the biggest strengths of the SUE process. It’s designed to be strategic and cost-effective. You can apply different quality levels to different parts of your site based on risk. A common approach is to use a broad Quality Level B investigation across the entire project area to get a clear map of where utilities are located. Then, you can use targeted, high-precision Quality Level A test holes only at critical conflict points, like where a new foundation will be poured next to a critical gas line.

What kind of project actually needs SUE? SUE is valuable for nearly any project that involves breaking ground, but it becomes critical in certain situations. It’s essential for projects on sites with dense underground infrastructure, properties with poor or missing utility records, or any job that involves deep excavations or soil borings. We see it used for everything from planning new building construction and roadway expansions to executing site upgrades. If a utility strike would cause significant delays, costs, or safety hazards for your project, then SUE is a necessary investment.

What do I receive after a SUE investigation is complete? The primary deliverable is a detailed, professional map of your site’s subsurface utilities. This isn't just a simple sketch. Each utility is clearly identified and labeled with the SUE quality level used to locate it, so your team immediately understands the reliability of the data for each line. This map is typically delivered as a CAD file, a GIS layer, or a PDF, ready to be integrated directly into your engineering and design plans.

How does SUE actually save my project money? SUE saves money by preventing expensive problems before they happen. The cost of a single utility strike—including emergency repairs, crew downtime, and potential fines—can easily eclipse the entire cost of a thorough SUE investigation. By providing accurate data early in the design phase, SUE helps you avoid conflicts that would otherwise lead to costly project redesigns and change orders during construction. It replaces guesswork with certainty, protecting your budget and your schedule from unexpected subsurface surprises.