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Subsurface Utility Engineering Quality Levels

In 2003, the American Society of Civil Engineers (ASCE) published Standard 38-02 titled Guideline for the Collection and Depiction of Existing Subsurface Utility Data. The standard defined SUE and provided guidance for the collection and depiction of subsurface utility information. The ASCE standard presents a system to classify the quality of existing subsurface utility data, in accordance with four quality levels:
  • Quality Level D. QL-D is the most basic level of information for utility locations. It comes solely from existing utility records or verbal recollections. QL-D is useful primarily for project planning and route selection activities.
  • Quality Level C. QL-C involves surveying visible above ground utility facilities (e.g., manholes, valve boxes, etc.) and correlating this information with existing utility records (QL-D information).
  • Quality Level B. QL-B involves the application of appropriate surface geophysical methods to determine the existence and horizontal position of virtually all subsurface utilities within a project’s limits.
  • Quality Level A. QL-A, also known as "daylighting", is the highest level of accuracy presently available. It provides information for the precise plan and profile mapping of underground utilities through their actual exposure, and also provides the type, size, condition, material and other characteristics of underground features. Exposure is typically achieved through hand digging or Hydro-Vacuuming.

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