Top 5 Methods Used in Utility Surveys

PAS 128 Utility Surveys  are essential for identifying and mapping underground infrastructure such as cables, pipes, and ducts before construction or excavation begins. These surveys help prevent costly damages, project delays, and safety hazards. Various methods are employed depending on the site conditions, utility types, and the required level of accuracy. Below are the top five most commonly used methods in utility surveys:

1. Ground Penetrating Radar (GPR)
Ground Penetrating Radar is a non-invasive technique that uses high-frequency radio waves to detect buried objects. A GPR unit sends electromagnetic pulses into the ground, which reflect off underground structures and return to the surface for analysis. GPR is especially useful for detecting non-metallic utilities like plastic pipes, as well as changes in soil composition or voids. It provides a detailed image of subsurface features, making it ideal for areas where digging is restricted. However, the effectiveness of GPR can be reduced in areas with high moisture or clay content.

2. Electromagnetic Location (EML)
Electromagnetic location, or cable locating, is a technique used to trace metallic utilities such as electric cables and metal pipes. It involves using a transmitter to send an electromagnetic signal along a utility line and a receiver to detect the signal above ground. EML is fast, reliable, and commonly used to locate both active and inactive utility lines. It is often used in combination with GPR for more comprehensive results, especially on complex sites with both metallic and non-metallic utilities.

3. Utility Mapping via Global Positioning System (GPS) and Geographic Information System (GIS)
GPS and GIS technologies are used to accurately record the location of utilities on a digital map. Once utilities are detected using other methods like GPR or EML, surveyors mark the exact positions using GPS devices. These data points are then integrated into GIS platforms, enabling easy access, storage, and management of utility information. This method provides a long-term solution for utility documentation and helps stakeholders visualize data spatially, improving planning and coordination.

4. Vacuum Excavation (Potholing)
Vacuum excavation, or potholing, is a minimally invasive method used to expose underground utilities with high accuracy. It involves using pressurized air or water to loosen soil around a utility, which is then vacuumed out. This technique is considered one of the most reliable methods for verifying utility depth and type, especially in congested areas. It’s often used to validate findings from non-invasive techniques before actual excavation begins. Although more costly and time-consuming, it greatly reduces the risk of damaging critical infrastructure.

5. CCTV Drain and Pipe Surveys
Closed-Circuit Television (CCTV) surveys are widely used to inspect the condition and alignment of underground drainage and sewer systems. A small camera is inserted into the pipeline, transmitting real-time video to the operator. This allows surveyors to identify blockages, defects, and connection points without excavation. CCTV surveys provide visual confirmation and detailed reports, which are crucial for maintenance planning and infrastructure upgrades.

Conclusion
Each utility survey method has its own strengths and ideal applications. Often, a combination of these techniques is used to ensure accuracy, safety, and compliance with regulations. By employing the right mix of survey methods, developers and engineers can prevent costly errors and make informed decisions during project planning and construction.