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Subsurface Utility Engineering (SUE) is a specialized branch of engineering that involves the collection, depiction, and management of utility data. It is primarily used to identify the location, quality, and characteristics of underground utilities such as water pipes, electrical cables, gas lines, and telecommunications conduits. The purpose of SUE is to provide accurate and reliable information that can help engineers, planners, and construction teams avoid utility conflicts, minimize risks, and prevent costly damage during excavation and construction projects.
SUE typically involves the use of various techniques and technologies, including ground-penetrating radar (GPR), electromagnetic locating, vacuum excavation (also known as potholing), and utility mapping. The information gathered through SUE is classified according to the ASCE 38-22 standard, which defines four quality levels (A, B, C, and D) based on the accuracy and method of data collection.
Overall, SUE is an essential process for ensuring the safety and efficiency of infrastructure projects by accurately identifying and mapping existing underground utilities.
Description: Quality Level D is the most basic level of information for utility data. It involves the collection of existing records or oral recollections about the utilities in the project area. This data is generally obtained from utility owners, public agencies, or other relevant sources and compiled to form an initial utility map.
Use: QLD is typically used for preliminary design purposes, such as early planning stages and feasibility studies, where general utility locations are needed.
Description: Quality Level C involves surveying visible utility facilities, such as manholes, valve boxes, and other surface features, and correlating this information with the data collected in QLD. This level provides a more reliable utility map by combining surface evidence with existing records.
Use: QLC is used for design projects where more accurate utility locations are required than those provided by QLD but without the need for extensive field verification.
Description: Quality Level B involves the use of surface geophysical techniques to determine the existence and horizontal position of subsurface utilities. This level provides a higher degree of accuracy by detecting utilities that may not have visible surface features.
Use: QLB is suitable for projects requiring a more accurate and reliable depiction of subsurface utilities, such as during detailed design and preliminary construction planning.
Description: Quality Level A provides the highest level of accuracy for utility data, involving the precise location of utilities through physical exposure (e.g., potholing, daylighting). This level determines both the horizontal and vertical positions of utilities and verifies their size, material, and condition.
Use : QLA is essential for final design and construction activities where precise utility locations are critical to avoid conflicts and damage during excavation.
The Federal Highway Administration (FHWA) tasked Purdue University with evaluating the impact of Subsurface Utility Engineering (SUE) on reducing costs and delays in highway projects. The effectiveness study was conducted and the results were significant. A savings of $4.62 for every $1.00 spent on SUE was quantified from a total of 71 projects. These projects had a combined construction value in excess of $1 billion. The costs of obtaining Quality Level “B” (QLB) and Quality Level “A” (QLA) data on these 71 projects were less than 0.5 percent of the total construction costs, yet they resulted in a construction savings of 1.9% compared to using traditional Quality Level “C” (QLC) and Quality Level “D” (QLD) data.
Utilizing SUE provides a structured approach to utility data collection, ensuring that project designers and engineers have the necessary information to make informed decisions and minimize the risks associated with subsurface utilities. The ASCE 38-22 standards help achieve a balance between data accuracy and project needs, supporting successful project outcomes.