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The AS5488.1-2019: Classification of Subsurface Utility Information (SUI) standard is the cornerstone of safe, efficient, and reliable utility locating services. By following these guidelines, we ensure that every project is completed with precision, compliance, and safety in mind.
QL-D represents the lowest level of accuracy and relies on indirect methods to gather subsurface utility information. This level is based primarily on available records or existing utility maps and does not involve any physical verification of the actual location of utilities.
Methods
Information is obtained from existing records, utility drawings, and historical data.
Accuracy
The location and extent of utilities may be uncertain or approximate, and the reliability of the data depends on the quality of the historical records or previous mapping.
Use
QL-D is typically used in the early planning stages, where detailed knowledge of utility locations is not yet required.
Limitations
High potential for inaccuracies or omissions due to outdated or incomplete records.
QL-C involves more advanced methods than QL-D, using surface geophysical techniques to detect utilities without directly disturbing the ground. These methods provide non-invasive data but still lack precise verification.
Methods
Techniques like electromagnetic induction (EMI), ground-penetrating radar (GPR), and other non-destructive methods to locate utilities from the surface.
Accuracy
The data obtained is more reliable than QL-D, but the actual location and depth of utilities may not be fully accurate. The resolution depends on the technology used and environmental conditions.
Use
Typically used for a preliminary survey or when utilities are suspected to be in a particular area but cannot be confirmed through direct means.
Limitations
Surface geophysical methods can have limitations in differentiating between different types of utilities, and certain materials (e.g., concrete, non-metallic pipes) may be harder to detect.
QL-B provides more accurate information by combining visual survey techniques with indirect detection, offering a clearer understanding of the utilities’ approximate location and type.
Methods
A combination of surface survey data, geophysical methods, and limited potholing (excavation at a few key points to expose utilities) or excavation in select areas.
Accuracy
QL-B provides better accuracy than QL-C, but still, the utility location might not be fully verified across the entire area of interest. The potholing helps confirm the location of some utilities.
Use
Commonly used when more information is needed than what is provided by QL-D or QL-C, especially when planning new construction or renovation projects that involve areas with known utility infrastructure.
Limitations
Though potholing confirms utility presence and location at specific points, it does not provide full coverage or verification across the entire site. Potholing is time-consuming and can be costly.
QL-A represents the highest level of accuracy and involves direct physical verification of the utility’s location and depth using potholing or other direct methods to expose and measure the utility infrastructure.
Methods
Direct physical exposure through potholing, where small, controlled excavations are made to locate and expose buried utilities. Techniques may also include the use of vacuum excavation (suction) or hydro-excavation (pressurized water).
Accuracy
QL-A provides the most accurate and reliable data. Utilities are directly measured for location, depth, and condition. The data is highly precise and reliable for construction planning and design.
Use
This level of quality is often required for high-risk projects, projects near critical infrastructure, or when utilities need to be accurately located to avoid damage or conflicts with new construction.
Limitations
Potholing is more costly and labor-intensive than other methods, and it may not be practical for large-scale areas. However, the benefits in terms of safety and precision are typically worth the additional effort.
QL-B provides more accurate information by combining visual survey techniques with indirect detection, offering a clearer understanding of the utilities' approximate location and type.
Potholing (QL-A) is costly and time-consuming. For large areas, a combination of QL-C and QL-B can provide a balance between cost and accuracy.
Some utility types, especially those that are non-metallic or deeply buried, may require more advanced methods like potholing (QL-A) for accurate location identification.
Some utility types, especially those that are non-metallic or deeply buried, may require more advanced methods like potholing (QL-A) for accurate location identification.
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