Clarity Below. Confidence Ahead.

Following are the four quality levels of subsurface utility engineering, according to the Federal Highway Administration, adapted from their definition:

Quality Level D: The most basic level of information for utility locations. Comes solely from existing utility records or verbal recollections; both are limited in terms of comprehensiveness and accuracy. Useful primarily for project planning and project site selection.

Quality Level C: Involves surveying visible utility facilities (e.g., manholes, valve boxes, etc.) and correlating this information with existing utility records. Often this information shows that many underground utilities have been omitted or erroneously plotted. Useful for planning and projects where utilities are not prevalent or are not too expensive to repair or relocate.

Quality Level B: Involves the application of surface geophysical methods such as electromagnetic locating or ground penetrating radar to “designate” the existence and horizontal position of utilities within the project limits. Information obtained is surveyed to project control. Addresses problems caused by inaccurate utility records, abandoned or unrecorded facilities, and lost references. Information can be used for preliminary engineering decisions regarding location of storm drainage systems, footers, foundations, and other design features to avoid conflicts with existing utilities. Slight adjustments in design can produce substantial cost savings by eliminating utility relocations.

Quality Level A: Known as “locating,” this level provides the highest accuracy and involves full use of SUE services. Provides information for the precise plan and profile mapping of underground utilities through the nondestructive exposure of underground utilities, surveyed to project control. Also provides the type, size, condition, material, and other characteristics of underground features.

The appropriate quality level depends on the project stage, utility risk, design needs, and the consequences of a potential conflict. Quality Level D and Quality Level C information may be appropriate for early planning, while Quality Level B is commonly used to map the approximate horizontal position of utilities throughout a project area early in design. Quality Level A uses physical exposure and survey measurements to establish precise horizontal and vertical utility information at critical locations. Many projects benefit from a combination of quality levels, such as Quality Level B throughout the project limits and targeted Quality Level A test holes at potential utility conflicts and proposed gravity sewer crossings. Ayres can help determine where each quality level provides the greatest value for your project.

811, One Call, and Diggers Hotline locating are damage-prevention services intended to mark participating utility owners’ facilities before excavation. It is not designed to provide comprehensive, survey-grade utility information for project planning or design. Subsurface utility engineering (SUE) is performed under the responsible charge of a professional (PE, PLS, etc.) and combines utility records, field observations, geophysical locating, surveying, and – when needed – physical exposure through test holes. The resulting utility information is documented at defined quality levels to help designers identify conflicts, reduce uncertainty, and make informed project decisions. SUE complements – but does not replace – required One Call notification before excavation.