• Subsurface utility engineering

    Subsurface utility engineering

    • Subsurface Utility Engineering (SUE) is a branch of engineering practice that involves managing certain risks associated with utility mapping at appropriate quality levels, utility coordination, utility relocation design and coordination, utility condition assessment, communication of utility data to concerned parties, utility relocation cost estimates, implementation of utility accommodation policies, and utility design.

      The SUE process begins with a work plan that outlines the scope of work, project schedule, levels of service vs. risk allocation and desired delivery method. Non-destructive surface geophysical methods are then leveraged to determine the presence of subsurface utilities and to mark their horizontal position on the ground surface. Vacuum excavation techniques are employed to expose and record the precise horizontal and vertical position of the assets. This information is then typically presented in CAD format or a GIS-compatible map. A conflict matrix is also created to evaluate and compare collected utility information with project plans, identify conflicts and propose solutions. The concept of SUE is gaining popularity worldwide as a framework to mitigate costs associated with project redesign and construction delays and to avoid risk and liability that can result from damaged underground utilities.

      The practice of collecting, recording and managing subsurface data has historically been widely unregulated. In response to this challenge, in 2003, The American Society of Civil Engineers (ASCE) developed standard 38-02: Guideline for the Collection and Depiction of Existing Subsurface Utility Data, which defined the practice of SUE. Many countries followed the U.S. lead by creating similar standards including Malaysia, Canada, Australia, Great Britain and most recently, Ecuador. Developed and refined over the last 20 years, SUE classifies information according to quality levels with an objective to vastly improve data reliability. This provides project owners and engineers with a benchmark to determine the integrity of utility data at the outset of an infrastructure project.

      A number of standards of care have been developed to govern the use of SUE.

      In 2003, the American Society of Civil Engineers (ASCE) published Standard 38-02 titled Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data. The standard defined SUE and set 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 the actual exposure of underground utilities (usually at a specific point), 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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    • Subsurface utility engineering