First, up in our series on engineering disciplines is Subsurface Utility Engineering often referred to as SUE. This engineering discipline is lesser-known than many of its counterparts, such as civil engineering or structural engineering. While it may be less familiar, it plays a crucial role in land development and construction projects. As Landmark’s SUE Leader Skip McIntosh points out, “The lack of reliable information on the location of underground utilities during construction activities can result in costly conflicts, damages, delays, utility service disruptions, redesigns, claims, injuries and, even, lost lives.”

Now that we understand the critical role of Subsurface Utility Engineering in development projects let’s dive into what exactly it is they do. Subsurface Engineers’ primary function is to identify any and all underground utilities to avoid expensive and dangerous mistakes during the construction process. SUE is an engineering discipline that, according to the US Department of Transportation, has evolved significantly over the past several decades and is a process that combines civil engineering, surveying, and geophysics. As Subsurface Engineering continues to grow, the adoption of technology, including vacuum excavation and surface geophysics, is becoming more common and, in some states, is a requirement. That being said, while technology is essential, The American Society of Civil Engineers (ASCE) Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data was published and distributed in 2003. The ASCE standard makes it very clear that SUE is a process, not a technology. It defines SUE as a branch of engineering practice that involves managing certain risks associated with:

  • utility mapping at appropriate quality levels,
  • utility coordination,
  • utility relocation design and coordination,
  • utility condition assessment,
  • communication of utility data to concerned parties,
  • utility relocation cost estimates,
  • implementation of utility accommodation policies, and
  • utility design.

These responsibilities are often combined with traditional records and site surveys while also leveraging new technologies like surface geophysical methods and vacuum excavation to provide information on quality levels.

Let’s take a look at the most common and largest Subsurface Engineering activities in more detail. According to the Federal Highway Administration, the major SUE activities are as follows.

Scope of Work – The process of developing a written project-specific work plan package that consists of scope of work, levels of service vs. risk allocation, project schedule, and desired project delivery method. This SUE work plan package is agreed upon by the SUE provider and the client, describing the SUE work to be performed.

Designating – The process of using a surface geophysical method or methods to interpret the presence of a subsurface utility and mark its horizontal position on the ground surface or on above-ground surface markers.

Locating – The process of exposing and recording the precise vertical and horizontal location and providing utility size and configuration of a utility.

Data Management – The process of surveying, designating and locating information to project control and transferring it into the client’s CADD system, GIS files, or project plans.

Conflict Analysis – The engineering process of using a conflict matrix to evaluate and compare depicted designating information with proposed plans (highway, bridge, drainage, and other) in order to inform all stakeholders of potential conflicts, potential resolutions, and costs to cure.

Within the significant activities, the Colorado Department of Transportation recommends SUE tasks are performed in the following order.

SUE Task Order Procedures 

  1. The CDOT Region Utility Engineer (RUE), in coordination with (as appropriate) the CDOT project manager, resident engineer, and region survey coordinator, must develop a project-specific Scope of Work and send it to the SUE consultant on CDOT letterhead. Examples for previous projects may be obtained either from other RUEs or the Headquarters Utilities Unit.Also, each of the two SUE NPS contracts that have been established includes the original Scope-of-Work for the NPS contract. The NPS Scope-of-Work can be used as a starting point for developing the project-specific Scope-of-Work. Copies of the NPS Scope-of-Work can be obtained either from the RUE, or the HQ Utilities Unit.
  2. The RUE, working with the project manager, must prepare a CDOT cost estimate for the work described in the project Scope of Work. Examples of previous project cost estimates are also available from the RUE or Headquarters Utilities Unit.
  3. The consultant must review the Scope of Work scope and prepare a Task Proposal with their own cost estimate. It may be necessary to negotiate work items and/or costs. Once agreement on the work and costs is reached, the consultant must submit three original signed copies of the Task Proposal.
  4. The RUE must obtain written approval of the Task Proposal from the regional transportation director (RTD); an email is sufficient.
  5. A CDOT standard Task Order Letter must be filled out to the extent possible (some items must be completed by the Headquarters Agreements Office later on), and the Region Business Office must generate a PG document. The standard Task Order Letter form may be obtained from the Region Business Office.
  6. The following items must then be sent to the CDOT HQ Agreements. Three copies of each of the following:
    • The original CDOT Scope of Work and cover letter that was sent to the consultant on CDOT letterhead
    • The CDOT RUE/Project Engineer cost estimate of the work
    • All three original signed copies of the consultant’s Task Proposal
    • The partially completed Task Order Letter
    • The PG document
    • Unless an approval email has already been forwarded to Mike Como, written approval from the RTD
  7. The Headquarters Agreements Office will process the Task Order for all final approvals. Once such approval is obtained, the Agreements Office will coordinate issuance of the Notice to Proceed letter with the Region. The consultant may not proceed with any work until the NTP letter has been sent out.


In addition to SUE activities and processes, quality plays a significant role in executing SUE service services. The American Society of Civil Engineers (ASCE) has developed an important standard of care guideline, Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data, CI/ASCE 38-02.

This standard guideline describes four quality levels of utility depiction:

Quality Level D – Information derived from existing records or oral recollections.

Quality Level C – Information obtained by surveying and plotting visible above-ground utility features and by using professional judgment in correlating this information to Quality Level D.

Quality Level B – Information obtained through the application of appropriate surface geophysical methods to determine the existence and approximate horizontal position of subsurface utilities.

Quality Level A – Precise horizontal and vertical location of utilities obtained by the actual exposure and subsequent measurement of subsurface utilities, usually at a specific point.


What industries need SUE services?

At Landmark, our Subsurface Utility Division works with a number of different industries. Our services are typically availed by Engineering firms, Utility companies, State and local governments, Drilling companies, and Excavation companies

We hope this helps provide a greater understanding of Subsurface Utility Engineering. If you’re in need of SUE services, click here to schedule a call to discuss your project.