Subsurface Utility Engineering

Quality Level D (QL-D) – Records Research

Quality Level D is the foundation of every SUE investigation. At this level, we collect and review existing utility records from owners, municipalities, and other available sources to identify the approximate presence of underground utilities within a project area. This may include as-builts, atlases, GIS data, and institutional knowledge (which sometimes lives in a filing cabinet from 1987). QL-D provides valuable early planning information and helps identify potential conflicts before design progresses too far. While it represents the most preliminary level of data, it is an essential first step in understanding underground risk and setting expectations appropriately.

Quality Level C (QL-C) – Surface Feature Survey

Quality Level C enhances the records research by correlating visible surface features with underground utility records. This includes surveying features such as valve boxes, manholes, pedestals, hydrants, cleanouts, and other appurtenances to refine the horizontal position of utilities. In short, we connect what’s drawn on paper to what’s physically in the field. QL-C improves accuracy over QL-D and often reveals discrepancies between record drawings and reality because, as every engineer knows, “as-built” does not always mean “as-exactly-constructed.” Often, it does not! QL-C provides a more reliable depiction of utility alignments and helps reduce surprises during design and construction.

Quality Level B (QL-B) – Geophysical Designating

Quality Level B involves field designating of underground utilities using geophysical methods such as electromagnetic locating, rodders, and sondes. These technologies allow us to identify and mark the approximate horizontal position of subsurface utilities without excavation and is generally accurate within 6 inches horizontally. QL-B significantly reduces the risk of utility conflicts and is often the most cost-effective risk mitigation step during design.

In fact, studies have been conducted by Purdue, Penn State, and Texas A&M University that incorporated over 100 civil project found that for every $1 spent on SUE, there was a return on investment of between $11.30 and $22.21, depending on the size of the project. The larger the project, the bigger the savings!

Where do these saving come from you may ask? When QL-B is performed and utilities are identified in the early stages of a project, you avoid unexpected utility conflicts, delays, and unnecessary utility relocations. Those are all great places to reduce risk as much as possible!

Quality Level A (QL-A) – Vacuum Excavation (Test Holes)

Quality Level A provides the highest level of accuracy and confidence by exposing utilities through non-destructive vacuum excavation (potholing). This process allows us to visually confirm the exact horizontal and vertical position of utilities, as well as identify size, material, and condition. QL-A delivers survey-grade data that designers and contractors can rely on when precision matters most. If QL-B tells us where a utility is, QL-A tells us exactly where it is, and how deep, without leaving anything to interpretation. It is the gold standard of SUE and the level that turns assumptions into measurements. It is the most precise data that we offer!