The 4 ASCE SUE Quality Levels: A Field Guide

Think of subsurface utility data like a school report card. Some information is based on old notes and hearsay, while other data comes from direct, hands-on verification. You wouldn't build a critical project based on a C-minus report, and the same logic applies to what's underground. The ASCE SUE Quality Levels provide this exact grading system for your utility information. Ranging from D to A, each level represents a different degree of effort and reliability. This simple, standardized framework removes the guesswork, helping you understand the confidence you can place in your data and make smarter, safer decisions for your project.

Key Takeaways

• Choose the Right Level for the Job: SUE Quality Levels are a flexible tool for managing risk, not a one-size-fits-all requirement. Apply higher-accuracy levels like QL-B and QL-A strategically in critical areas to get the certainty you need without overspending on data for your entire site.
• Certainty Comes from Technology: While initial levels rely on records and visual checks, reliable utility data requires advanced tools. Quality Level B uses geophysical equipment like GPR to detect utilities from the surface, while QL-A provides absolute verification by physically exposing them with non-destructive methods.
• Integrate Subsurface Data from Day One: Treat your SUE map as a core project document, not just a pre-dig check. Share it with designers to prevent conflicts, use it to coordinate with field crews for safer excavation, and archive it to make future site work more efficient.

What Are ASCE SUE Quality Levels?

When you’re planning an excavation, the last thing you want is a surprise. Subsurface Utility Engineering (SUE) is a systematic process that helps you avoid them by investigating, identifying, and documenting underground utilities. To make this process clear and consistent, the American Society of Civil Engineers (ASCE) created a set of standards. Think of them as a grading system for the quality and reliability of your utility data, ensuring everyone on the project is speaking the same language.

These standards, officially known as ASCE 38-22, outline four distinct "Quality Levels" (QLs). Each level, from D (the lowest) to A (the highest), represents a different degree of accuracy and effort. For example, Quality Level D relies solely on existing records, while Quality Level A requires physically exposing the utility to verify its exact location. This framework isn't just about finding pipes and cables; it’s about managing risk. By choosing the right quality level for your project, you can make informed decisions, prevent costly utility strikes, and keep your team safe. It gives you a clear, standardized way to specify and receive the utility information you need to design and build with confidence.

A Quick History of Utility Mapping Standards

Before SUE became a standardized practice, utility mapping was often a chaotic mix of old records, guesswork, and luck. The goal was simple but challenging: find every utility within a project's limits, whether it was on a map or not. This need for a more reliable system led to the development of the SUE process. The core idea was to create a framework that moved beyond just looking at existing records and incorporated modern geophysical techniques and direct observation. The ASCE 38 standard was born from this effort, providing a common language for engineers, contractors, and locators to communicate the reliability of subsurface data.

How SUE Fits into Your Project Plan

Think of SUE as a critical part of your project's planning and design phase, not an afterthought. You apply SUE in a structured way, following the quality levels outlined in the ASCE 38-22 standard. This isn't a one-size-fits-all approach. The beauty of the quality level system is its flexibility. As a project owner or manager, you get to decide how much certainty you need. For a simple landscaping project, lower-quality data might be enough. But for complex excavations or directional drilling, you’ll need higher-quality information to manage your risk. This allows you to tailor your subsurface utility mapping efforts to the specific demands of your job site.

Why These Quality Levels Matter

At their core, SUE Quality Levels are all about managing risk. Each level corresponds to a degree of certainty, helping you understand how much information you truly need to design and build your project safely and efficiently. Familiarizing yourself with these levels empowers your team to make smarter decisions from the start. Instead of guessing what’s underground, you can budget appropriately for the necessary utility investigations and avoid the costly delays and change orders that come from unexpected discoveries. It transforms subsurface data from a liability into a valuable asset, giving you a clear picture of what lies beneath before the first shovel ever hits the ground.

Quality Levels D & C: The Starting Point

Think of Quality Levels D and C as the essential homework you do before starting any major project. These initial stages are all about gathering existing information and getting a feel for the landscape without ever putting a shovel in the ground. They rely on records and visual cues to build a preliminary picture of the subsurface. While they are the least accurate of the four levels, they form the foundation for all subsequent, more precise investigations.

This phase is crucial for early-stage planning and budgeting. It helps you identify potential red flags and understand the general utility congestion in your project area. However, it's important to remember that this data is based on historical information and surface-level observations, which can be incomplete or outdated. For any work that involves excavation, you’ll need to move on to higher quality levels. But for now, let’s look at where every subsurface investigation begins.

Quality Level D: What Existing Records Tell You

Quality Level D is the starting point for any subsurface utility investigation. It involves collecting and reviewing existing utility records for your project area. This is purely a "desktop" exercise, gathering information from sources like as-built drawings, utility maps, municipal records, and even interviews with long-time site personnel. The goal is to get a rough idea of what utilities might be present.

The major limitation here is reliability. Records can be inaccurate, incomplete, or decades out of date. A utility line shown on a 30-year-old map may have been moved or abandoned long ago. According to the Federal Highway Administration, this level provides a general sense of utility presence but isn't precise enough for design or construction.

Quality Level C: What You Can See on the Surface

Quality Level C takes the information from QL-D and adds a layer of real-world context. This involves a visual site survey to identify and map all visible, above-ground utility features. Think manholes, valve boxes, fire hydrants, utility poles, and communication pedestals. A surveyor will plot the precise location of these features and correlate them with the records gathered in QL-D.

This step helps connect the dots between the paper records and the physical site, offering a slightly more reliable picture. However, it still can't account for what you can't see. It often misses utilities that have no surface features, like abandoned lines or unrecorded reroutes. It’s a step up in confidence from QL-D, but still leaves significant gaps in your understanding of the subsurface.

When to Use Levels D & C

So, when is this level of information enough? Quality Levels D and C are best suited for the very early stages of project planning and feasibility studies. This data can help you route a proposed design around major known utility corridors or identify areas that will require more intensive investigation later on. According to ASCE standards, these lower levels are appropriate for areas where utility conflicts are not expected to be a major issue.

For example, you might use QL-C data to decide where to place a temporary access road or a staging area for materials. It gives you enough information to avoid obvious obstacles. However, this data should never be used to finalize design plans or to provide clearance for excavation.

How This Data Is Collected

The process for gathering QL-D and QL-C data is straightforward. For Quality Level D, the work involves contacting utility owners, visiting municipal record offices, and digging through project archives for any relevant drawings or maps. It’s an exercise in research and information gathering.

For Quality Level C, a survey crew visits the site to perform a visual inspection. They use survey-grade GPS or a total station to capture the coordinates of every visible utility feature. This data is then plotted on a map and overlaid with the QL-D record information to create a comprehensive, though still preliminary, utility map. This initial map becomes the baseline for more advanced utility locating services needed for QL-B.

Quality Levels B & A: Getting Precise

When you absolutely need to know what’s underground, Quality Levels B and A are where the real investigation begins. This is where we move past records and visual checks and get into the science of subsurface mapping. These levels use advanced technology to actively detect and verify utilities, giving you the precise data required to design confidently and dig safely. It’s about replacing assumptions with certainty.

Quality Level B: Detecting Utilities from the Surface

Quality Level B (QL-B) is the process of using geophysical tools to find the horizontal location of underground utilities. Think of it as a high-tech investigation from the surface. Our crews use equipment like Ground Penetrating Radar (GPR) and Electromagnetic (EM) locators to paint a picture of what’s buried beneath your site. This step is crucial because it identifies utilities that were missed in the records or aren't visible from above. By designating and marking utilities in the field, QL-B provides a reliable map that helps you avoid conflicts and plan your excavation with a much higher degree of confidence. It’s the most common level of service for design and damage prevention.

Quality Level A: Exposing Utilities for Certainty

Quality Level A (QL-A) is the gold standard for accuracy. This is where we physically confirm a utility's exact horizontal and vertical position by carefully exposing it. This process, often called "potholing," is typically done with non-destructive vacuum excavation to avoid damaging the line. QL-A provides precise, three-dimensional data that is essential for final design, especially when you’re working in a congested area or need to cross an existing utility. When you need absolute certainty about a utility’s depth and location before you break ground, QL-A is the only way to get it. It removes all doubt and provides verifiable, survey-grade data.

The Technology Behind Levels B & A

The tools we use for these higher quality levels are what set professional SUE providers apart. For QL-B, our primary instruments are GPR and EM locators, which allow us to perform comprehensive utility locating services across your entire project area. For QL-A, we rely on vacuum excavation trucks to safely dig test holes. These technologies work hand-in-hand. The data from a QL-B sweep helps us pinpoint the most critical spots to perform QL-A verification. This integrated approach is efficient and ensures we gather the most accurate data exactly where you need it, preventing unnecessary digging and saving you time and money.

How to Meet High Accuracy Standards

Achieving a high standard of accuracy on your project starts with you. As the project owner or manager, you can specify the SUE quality level needed for different parts of your site. You don't always need QL-A data for an entire project; you can apply it strategically to high-risk areas. The key is to match the quality of the data to the risk you're willing to accept. By incorporating ASCE 38-22 standards into your project plans from the beginning, you create a clear scope of work that ensures you get the reliable subsurface data you need to prevent costly utility strikes and redesigns during construction.

How to Choose the Right Quality Level

Deciding on the right SUE Quality Level isn’t about always aiming for the highest one. It’s about making a smart, strategic choice that fits your specific project. Think of it as a dial you can turn up or down depending on what you’re trying to accomplish. The goal is to gather just the right amount of information to move forward confidently without overspending on data you don’t need. By considering your project’s scope, risk, budget, and any applicable rules, you can pinpoint the exact quality level that will set you up for success.

Match the Quality Level to Your Project

Every project has unique needs, and the SUE process is flexible enough to meet them. The ASCE standard notes that this system "allows project owners to decide what quality level of information they want to apply to their risk management challenge." Are you planning a few simple soil borings in an open field, or are you trenching for a new fiber line through a dense urban corridor? The first scenario might only require Quality Level C or D to get started, while the second demands the precision of Quality Level B or A in critical areas. Start by mapping out your project’s specific activities and identify where the highest potential for conflict with underground utilities exists.

Factor in Your Project's Risk

At its core, choosing a quality level is an exercise in risk management. You can think of the different levels as "degrees of risk, or how much information is really needed to adequately design and construct a project." A lower quality level comes with higher uncertainty and, therefore, higher risk. If you’re working around a hospital’s primary power feed or a major communications duct bank, the risk of a utility strike is incredibly high. In these situations, investing in Quality Level A or B isn’t just a good idea—it’s essential for protecting your assets, your team, and your timeline. Our utility locating services are designed to help you manage that risk with clear, reliable data.

Balance Your Budget with Your Needs

While we’d all love to have perfect, survey-grade data for every square foot of a project site, budgets are a real-world constraint. SUE Quality Levels allow you to "balance their budget with the level of detail required for their specific project." You don’t have to apply the same quality level across your entire site. A smart approach is to use Quality Levels D and C for initial planning and broad area assessments, then strategically invest in Quality Levels B and A for the most congested or high-consequence zones. This hybrid method ensures you get precise data exactly where it matters most, making the best use of every dollar.

Stay Compliant with Regulations

Sometimes, the choice of quality level is guided by external requirements. Many government agencies and municipalities have adopted SUE standards to ensure safety and efficiency, especially for public works. For example, the Federal Highway Administration notes that many states "identify the quality of subsurface utility information needed for highway plans." Even if your project is on private land, you may be subject to local ordinances or your own company’s internal safety protocols that mandate a certain level of utility investigation. Always check for any applicable Subsurface Utility Engineering regulations or standards before you begin to ensure your project plan is fully compliant.

Put SUE Quality Levels into Practice

Knowing the SUE quality levels is one thing; using them effectively on a job site is another. Putting these standards into practice is about creating a clear, systematic approach to managing subsurface risk. It transforms the four quality levels from abstract concepts into a practical toolkit for planning, communication, and execution. By building your project workflow around these standards, you ensure that everyone on your team—from designers to excavators—is working with the same clear understanding of what lies beneath the surface.

Plan and Document Your SUE Process

A successful SUE investigation starts long before any equipment arrives on site. The first step is to create a clear plan that outlines which quality levels you need for different parts of your project. Not every square foot of your site will require Quality Level A data. Your critical excavation zones might need the certainty of QL-A, while areas with less activity may only require QL-C or QL-B. This is where you get to be strategic. The ASCE 75-22 standard empowers you to match the quality of information to your specific risk tolerance. Document these decisions clearly, so your entire team understands the scope and limitations of the utility data in each area.

Set Up Your Quality Control

Once you have a plan, you need a way to ensure the work gets done right. A solid quality control process verifies that the utility data you receive meets the standards you specified. This means working with a subsurface utility mapping provider who not only performs the work but also provides transparent, verifiable results. Your QC process should involve reviewing all deliverables, from field sketches to final CADD files, to confirm they align with the requested quality levels. This step is crucial for building confidence in your data and making sure it’s reliable enough for critical design and construction decisions. It’s your best defense against inaccurate information that could lead to costly surprises later.

Keep Your Stakeholders Informed

Clear communication is essential for making SUE data effective. Everyone involved in the project, including engineers, designers, and field crews, needs to understand what each quality level means. A utility line designated as QL-B, for instance, has been detected but not physically verified, carrying a different level of risk than a QL-A located line. Using the SUE quality levels as a common language prevents dangerous assumptions and ensures the data is used appropriately. When your team is aligned, you can make smarter design choices, reduce the risk of utility strikes, and keep the project moving forward smoothly and safely.

Integrate the Right Technology

Achieving the right quality level depends entirely on using the right tools for the job. While QL-D and QL-C are based on records and visual observation, higher levels require advanced technology. To reach Quality Level B, your team needs sophisticated geophysical equipment like Ground Penetrating Radar (GPR) and Electromagnetic (EM) locators. For the certainty of Quality Level A, non-destructive vacuum excavation is necessary to expose and document the utility’s exact position. Partnering with a private utility locating service that has the right technology and the expertise to use it effectively is the only way to get the accurate, reliable data your project demands.

Get the Most from Your SUE Data

Once you have your SUE data, the real work begins. This information is more than just lines on a map; it’s a powerful tool that can shape your project’s success from start to finish. By treating your subsurface data as a strategic asset, you can streamline operations, protect your team, and make smarter decisions. Here’s how to put that data to work and get the best return on your investment.

Find Cost-Efficiencies

Think of high-quality SUE data as an insurance policy against budget overruns. The most significant savings come from avoiding the unknown. When you know exactly where utilities are, you can prevent costly strikes and the associated repairs and downtime. More strategically, accurate mapping helps you avoid unnecessary utility relocations, a major source of project delays and expenses. The Federal Highway Administration notes that this proactive approach keeps projects on schedule and on budget. By investing in accurate subsurface utility mapping upfront, you eliminate guesswork and prevent small issues from turning into expensive change orders down the line.

Mitigate Risk on Your Job Site

Every excavation project carries inherent risks, but SUE quality levels give you a framework to manage them effectively. Each level corresponds to a degree of certainty, allowing you to match the quality of your data to your project's risk tolerance. For a simple trench in an open field, a lower quality level might suffice. But for complex work near critical infrastructure, you need the certainty of Quality Level A data to ensure crew safety and prevent catastrophic damage. This isn't just about compliance; it's about making informed decisions to protect your people, your equipment, and your reputation. Choosing the right utility locating services is the first step in building a safer job site.

Integrate SUE Data into Your Workflow

SUE data is most valuable when it’s in the hands of everyone who needs it. The goal is to make subsurface information a seamless part of your project lifecycle, from initial design to final excavation. This means sharing detailed maps with engineers so they can design around existing infrastructure, coordinating with utility owners, and providing field crews with clear, actionable data. Modern GPS & GIS mapping makes this easier than ever, allowing you to overlay utility data onto project plans. When everyone is working from the same accurate information, you reduce miscommunication, streamline coordination, and keep the entire project moving forward smoothly.

Manage Your Data Effectively

The SUE report you receive today is an asset for tomorrow. Think of it as the foundational layer of your site's digital twin. Properly managing this data ensures its long-term value for future projects, maintenance, and facility upgrades. The key is to receive clean, engineer-ready results that are easy to access and interpret. Instead of a static PDF, ask for deliverables like CAD or GIS files that can be integrated into your existing systems. By treating your subsurface data as a permanent record, you build institutional knowledge, reduce the need for future surveys, and make every subsequent project on that site safer and more efficient.

Frequently Asked Questions

Is calling 811 the same as getting a SUE investigation? Think of 811 as the first step, not the whole journey. The 811 service is a free public notification system that asks utility companies to mark their lines up to your property's meter. A Subsurface Utility Engineering (SUE) investigation is a professional service you hire to find everything else. This includes private utilities on your property, abandoned lines, and unrecorded infrastructure that 811 doesn’t cover. SUE is a comprehensive risk management process, while 811 is a basic public safety notification.

Do I have to use the same quality level across my entire project site? Absolutely not. In fact, the smartest way to use SUE is to apply different quality levels strategically. You can use lower levels, like D and C, for broad planning in low-risk areas. Then, you can invest in higher-quality data, like B and A, only in the specific zones where you’ll be excavating, drilling, or working near critical infrastructure. This hybrid approach gives you the precise information you need where it matters most, without overspending on data for the entire site.

What's the real difference between Quality Level B and Quality Level A? The simplest way to think about it is "detecting" versus "confirming." For Quality Level B, we use geophysical tools from the surface to detect the horizontal location of a utility. It gives you a very reliable map of what's there. Quality Level A takes it a step further by physically exposing the utility, usually with safe vacuum excavation. This confirms its exact horizontal and vertical position, giving you precise depth information and removing all doubt.

How do I decide which quality level to request in my project plans? Your decision should be based on risk. Ask yourself: what are the consequences of hitting something in this specific area? If you're planning soil borings in an open field, a lower quality level might be sufficient for initial planning. But if you're trenching next to a hospital's main power line or a critical fiber optic cable, the high risk demands the certainty of Quality Level A. The more critical the area, the higher the quality level you should specify.

What kind of deliverable should I expect from a SUE investigation? You should expect much more than just paint on the ground. A professional SUE provider will deliver clear, usable data that integrates with your project workflow. This typically includes a detailed map, often in a digital CAD or GIS format, that shows the location and type of each utility marked with its corresponding quality level. This clean, engineer-ready data can be directly overlaid onto your design plans, ensuring everyone on your team is working with the same accurate information.