Subsurface Utility Engineering: [The Definitive Guide]

Subsurface Utility Engineering (SUE)

This guide will tell you what you need to know about Subsurface Utility Engineering, also known as SUE. 

Specifically, we will cover:

What SUE is, and how it differs from the more well known 811 miss utility markings.

• Who should think about hiring a SUE firm.

• The benefits of hiring a reputable company.

• Different quality levels set by ASCE (American Society of Civil Engineers) standards.

• More about the process and what to expect.

To start, let’s take a look at what exactly Subsurface Utility Engineering is, and then jump into when you should think about hiring a firm.

SUE: Defined.

Subsurface Utility Engineering or SUE is a type of civil engineering, and involves identifying buried utilities using a number of methods.

The utilities are identified by their horizontal and vertical position in the ground.

This data is used to provide survey grade locations, most commonly provided in a plat showing the utility locations.

Why is this information important?

SUE is done during the planning & design phase of various types of projects. Where utilities are located will dictate the risk associated with the project, what needs to be moved, what cannot be moved, timing, and other factors related to cost and feasibility.

More and more land is developed and redeveloped each year, especially in areas with job growth and needs for more housing. Companies are working hard to find more efficient methods to build. More than ever, they need to find out the feasibility and costs associated with a project with accuracy and speed. 

This is why consulting a SUE firm while you are in the planning phase is so important. We go over the numerous benefits below. 

Who Hires SUE Companies?

We have a wide range of clients who come to us with different projects of varying size and scope. 

In general, anybody who is planning to dig for a project, whether as a developer or just an addition on a single family home, should consider hiring an SUE firm. 

Some examples include: 

  • Geotechnical Engineering Firms
  • Land developers
  • Home builders & contractors
  • Homeowners

Other professionals also should consider using SUE services if they plan to do extensive excavation or design, whether for construction or another reason.

SUE vs. 811: Getting The Full Picture

There is occasional confusion around the difference between 811 and what a private SUE company does. Here are the differences. 

• 811 & Miss Utility

811 or Miss Utility is a nationwide service that connects anyone who needs to dig for a project, big or small, with the utility providers that have buried lines. 

The approximate locations of the utilities are marked with paint, flags or both. 

Calling 811 is required by law for anyone digging, and each state has a slightly different process. You can find out more information on their site

Miss Utility is a critical step in planning for your project. 

However, this alone may not give you the full picture of what lies beneath the surface. This is where a quality SUE firm is worth the investment.  

• When to Hire for Subsurface Utility Engineering (as well as call 811)

If you need a more thorough look at the utilities, including location, depth, size, condition, and mapping, then you want to look into getting a SUE firm.

Here is when to consider bringing in professionals. 

  • Private utilities need to be marked, not just public.
  • The site is complex, and you need accuracy.
  • You want a GIS map of all geophysical locatable utilities on a single map.
  • To lower the risk of potential costs and change orders during a project.
  • Prevent damage during excavation.
  • You want to test pit (visually locate) to get accurate depths of utilities.
A survey that shows the locations of utilities and also a public building. Color coded for different utility types.
An example of a survey completed by UPI, a SUE company. You can see the different utility types mapped.

Why Invest in SUE?

• More Efficient Planning

When you are planning and designing your project, you want to know, first and foremost, what is feasible and what is not. 

This can help you to figure out what needs to be redesigned up front and help prevent delays in the construction process by having to make changes after you have broken ground.

• Safety 

Knowing utility locations ahead of time will help your construction team avoid accidentally hitting a utility while digging. This keeps them and everyone in the area safe. 

• Liability & Cost

Damaging a utility during your construction process can be costly. In many cases, it is extremely costly. Not only will it delay your project but you could be liable for repairing the utility and potentially for any issues/costs associated with outages.

A surveyor uses a tool to locate utilities underground.
A UPI surveyor marking utilities using a pipe and cable locator.

SUE Quality Levels

• ASCE Standards

SUE has different quality levels that are defined by the standard 38-02 publication of the American Society of Civil Engineering. Each quality level will give more information about the utilities on the land you are working with, with Level A giving the most information with the highest level of accuracy.  

• Quality Level D

Level D is the most basic investigation, and may include: internet searches, reviewing existing surveys, records and maps, and even verbal recollections from others with knowledge of the property.

• Quality Level C

Quality level C combines existing records with an on site survey. This utilizes visual, above ground evidence as to the location of the utilities on the site to create a survey with existing information (water valves, fire hydrants, communication pedestals/vaults etc.) found above ground. 

• Quality Level B

This level uses non-invasive geophysical methods to find and map the horizontal location of the utilities. Various tools and technologies are used to locate the utilities, such as ground penetrating radar, electromagnetic profiling locators and other geophysical methods.

• Quality Level A

This is the highest level of quality for SUE, and offers the potential for the highest level of accuracy and a goal of providing both horizontal and vertical location of the utilities.

Utilities are exposed in this quality level, most commonly at a single point, using a combination of water/air and a large vacuum. This is commonly called daylighting, pot-holing, test pitting, or test holes utilizing a vacuum excavation truck. This can help show the condition, material, and size of the utilities that are present on the land.

The Process

Most efficiently, SUE professionals are called in during the planning phase of projects.

Once the scope of the project is confirmed, the SUE firm will begin to investigate the records of the subject land. Then comes the field investigation most commonly performed by two technicians. Once the surface markings (paint/flags) are down the field crew will begin to utilize survey equipment to provide survey grade locations of all utilities mapped on the project. Once the field work is completed, an AutoCAD technician will process and QC the data. They will add anything in as QL-D or QL-C based on the records received and begin to create a drawing and plat mapping the utilities. This plat is highly accurate and informative with specific utility notes from the investigation.

Once you have your plat with the utility markings, this is used to finalize your design, construction plans, or start excavation.


Subsurface Utility Engineering is a vitally important aspect of planning any project that involves excavation, design, development, or construction. Feel free to contact UPI with any questions or for help on any future projects where our services might be useful.

• About UPI

Utility Professionals Inc (UPI) has earned a stellar reputation as one of the premier SUE firms in the country. 

Headquartered in Northern VA, they have provided utility locating for major development projects in Virginia, Washington DC, Maryland and also internationally at the Rota Spain Naval Base. If you are interested in learning more, contact us today.

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