Innovations to Locate Stacked or Deep Utilities (2014)

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31 Subsurface Utility Engineering Quality Levels Highway plans typically contain disclaimers about the quality of utility information. The use of quality levels in the Subsur- face Utility Engineering (SUE) process allows designers to certify on the plans that a certain level of accuracy and com- prehensiveness has been provided. There are four quality levels: • Quality Level D information comes solely from existing util- ity records. It may provide an overall feel for the congestion of utilities, but it is often highly limited in terms of compre- hensiveness and accuracy. Its usefulness should be confined to project planning and route selection activities. • Quality Level C involves surveying visible aboveground util- ity facilities, such as manholes, valve boxes, and posts, and correlating this information with existing utility records. When using this information, it is not unusual to find that many underground utilities have been either omitted or erroneously plotted. Its usefulness, therefore, should be con- fined to rural projects where utilities are not prevalent or are not too expensive to repair or relocate. • Quality Level B involves the use of surface geophysical techniques to determine the existence and horizontal position of underground utilities. This activity is called “designating.” Two-dimensional mapping information is obtained. This information is usually sufficient to accom- plish preliminary engineering goals. Decisions can be made on where to place storm drainage systems, footers, foundations, and other design features to avoid conflicts with existing utilities. Slight adjustments in the design can produce substantial cost savings by eliminating util- ity relocations. • Quality Level A involves the use of nondestructive digging equipment at critical points to determine the precise hori- zontal and vertical position of underground utilities, as well as the type, size, condition, material, and other char- acteristics. This activity is called “locating.” It is the highest level presently available. When surveyed and mapped, pre- cise plan and profile information is available for use in mak- ing final design decisions. By knowing exactly where a utility is positioned in three dimensions, the designer can often make small adjustments in elevations or horizontal locations and avoid the need to relocate utilities. Addi- tional information, such as utility material, condition, size, soil contamination, and paving thickness, also assists the designer and utility owner in their decisions. The end product (the CADD file or project plans) may contain any or all of these quality levels. A p p e n d i x A