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What is Subsurface Utility Engineering?

Subsurface Utility Engineering (SUE) is a discipline of civil engineering that involves the investigation of buried utilities and identifies the conflicts they may pose to a project design in order to mitigate associated risks. These risks are identified through utility owner record drawings, geophysical methods to locate a utility’s horizontal position, vacuum excavation to pinpoint the vertical position, and the survey of this data referenced into a topographic map or various other types of mapping.*

Levels of SUE

SUE uses a series of four quality levels (QLs):

QL-D involves gathering record data, which may include digital records, paper records, internet searches, or site inspection.

QL-C entails surveying visible above-ground utility features, such as manholes, valve boxes, utility marker posts, and more. This information is then correlated with existing utility records.

QL-B determines the existence and horizontal position of underground utilities using surface geophysical techniques. This level also includes obtaining two-dimensional mapping information, which aids in decision-making for design, utility relocations, and installations.

QL-A is the highest and most effective SUE level presently available. Nondestructive digging equipment is used to determine the precise horizontal and vertical position of underground utilities. When surveyed and mapped, precise plan and profile information is available for design decisions and justification.

QLs are used to convey the level of confidence and the methods employed to determine a utility’s position. Once the QL has been determined, the SUE work has been performed, and a computer-aided design (CAD) file has been created depicting the best-known position of the utilities, a conflict matrix is produced to determine if utility relocation is needed for the project to be successful. Identifying the risks, including conflicts, in the matrix before a project starts is vital to the planning and design phases of a project.

*This process is approved by and defined in the ASCE 38-02 document “Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data.”

SUE Technologies

There are many different technologies and methods used to gather SUE data in the field. Some of those methods include vacuum excavation, electromagnetic locating, ground penetrating radar (GPR), acoustic systems, and metal detection. This data can be gathered through survey technologies such as Global Positioning Systems (GPS), Light Detection and Ranging (LiDAR), and Robotic Total Stations, then imported into CAD programs such as MicroStation, OpenRoads Designer, AutoCAD, and GIS.

How Does SUE Benefit You?

SUE is a proactive investment that helps owners anticipate and manage project risks early. Identifying the precise horizontal and vertical location of underground utilities can prevent change orders, costly project delays, damages, and negative PR. In a 2013 analysis, Kraus et al. collected and reviewed data from a number of Texas Department of Transportation (TxDOT) projects to identify the effects of SUE services on overall project cost, efficiencies, and delivery (1). The findings of this analysis demonstrated SUE’s positive impact on project performance, including the following benefits:

  • Lower design effort on a per-lane-mile basis

  • Less construction delay

  • Lower costs related to change orders associated with utilities during the construction phase

  • Minimal impact to total construction costs

SUE is also used as a preventative measure to ensure the safety of all workers on a construction project by identifying accurate utility locations prior to work zone activity. Additional benefits include improved working relationships with departments of transportation (DOTs), municipalities, and utility stakeholders; increased efficiency in surveying activities, and reduction of right-of-way acquisition costs.

SUE at Horrocks Engineers

SUE is used in any manner of public works projects where underground utilities may be encountered. Some of the different types of SUE projects that Horrocks has been involved in have included the Salt Lake City International Airport reconstruction, Tropicana Avenue roadway rehabilitation in Las Vegas, Kennecott Copper Mine, and various transportation projects for DOTs and municipalities.

In addition to subsurface utilities, Horrocks' utilities engineers are experts in coordination and design, asset management, and construction management. For more information on how Horrocks can efficiently and safely help your organization navigate the subsurface utility engineering process, contact Rod Brocious at (801) 763-5100 or email


  1. Kraus, E., Yingfeng, L., Overman, J., & Quiroga, C. (2013). Utility Investigation Best Practices and Effects on TxDOT Highway Improvement Projects. Texas Department of Transportation,


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