Understand What's Underneath™
Subsurface Utility Engineering is the process of depicting the location of underground utilities on civil drawings. The standards most commonly utilized for this process are produced by the American Society of Civil Engineers / Construction Institute. Also known as CI/ASCE 38-02, the code standardizes the Collection and Depiction of Existing Subsurface Utility Data.
The standard outlines four quality levels for the utility data that may exist on your drawings. The levels range from A through D, with Quality Level A being the most accurate, whereas Quality Level D data is the least reliable.
When you partner with Trinity Subsurface Engineering to provide utility data, we most commonly provide Quality Level B data. This is utility date that is obtained using surface geophysical equipment such as electromagnetic utility locating and ground penetrating radar.
Vacuum Excavation Services can be used to obtain Quality Level A utility data, such as depth, material, and precise location.
Subsurface Utility Engineering (SUE) is used to prevent costly unforeseen conflicts that are commonly discovered during the construction phase of a design project. SUE can help reduce risk to workers as well as reduce costs associated with unknown conflicts, such as re-engineering, utility conflict resolution, and utility relocation.
CI/ASCE 38-02 outlines four different quality levels for the depiction of subsurface utility data. Each quality level represents a different “reliability” for the utility information presented. The levels range from Quality Level D (least reliable) through Quality Level A (most reliable).
Quality Level D data is the least reliable form of utility data because it is information that is solely based on utility records and oral recollections. QL-D data should never be considered reliable enough for critical tie-ins or utility crossings.
Quality Level C data is slightly more reliable because it involves surveying and using professional judgement in correlating above ground utility features with QL-D data.
Quality Level B data is significantly more reliable that QL-C data because it is obtained in the field using surface geophysical equipment to designate the underground utility within an acceptable tolerance zone. The utilities are designated using paint and flags, which can be surveyed and plotted on project drawings. QL-B data is the most widely used quality level used when subsurface utility engineering is utilized.
Quality Level A data is the most reliable form of utility data because it involves physically exposing an underground utility using vacuum excavation. Once exposed, critical utility data can be collected including precise horizontal location and exact utility elevation. QL-A data is most commonly acquired at critical conflict points for proposed installations of structures or utility systems.
During a Quality Level B utility data investigation, several steps are taken to collect as much utility data as possible. Utility Records are researched from all utility companies and property owners in the vicinity of the project.
The project site is then scanned using our surface geophysical equipment, and existing underground utilities are designated on the surface using paint and flags.
Using survey equipment, the locations of the designated utilities are shot in using your established project control, or we can set new control if needed. Utility data can be delivered in a variety of formats including CADD and MicroStation. Utility data is presented as a standalone file that can be easily referenced into your existing civil drawings.
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