Underground Utility Damage Investigation
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Underground Utility Damage Investigation

 

Underground Utilities

When it comes to dealing with the myriad of hazards associated with excavation activities, a professional construction contractor must establish a comprehensive safety program addressing everything from trench safety to confined spaces. Most safety precautions are straightforward and definitive in mitigating dangers. However, there is one area that not only requires set precautions, but also demands constant attention, improvisation, and engagement: underground utility safety and damage prevention, also known as the 811 process.

Developed areas often have an underground maze of different municipal and utility networks and, while not as crowded, rural areas can contain buried transmission and communication lines. Various types of utilities are buried underneath the streets and roadways (underdrain, water, natural gas, oil, telephone cable, Sanitary and storm sewers, cable television, traffic signal, fiber optic, electric power, process piping, steam lines, and more). In addition, there are 2 different types of utility networks – Transmission (transmitting large quantities of natural gas, fuel, or electric power between utility facilities; often high volume under high pressure) or Distribution (Distributing natural gas, fuel, or electric power from a central location to area residences and businesses).

The consequences of damaging underground utilities during excavation work range from inconvenience (service outages and costly repair work) to disaster (large-scale property damage and loss of life). Hitting a major fiber optic duct bank can affect an entire region of the country. Hitting a telephone conduit can disrupt service to a neighborhood. When a water or sewer main is damaged during construction work the resulting flooding can fill excavated areas, jeopardizing workers and possibly leading to scour and erosion under adjacent roadways and structures. Breaking an oil pipeline can result in a spill that contaminates a large environmental area including sources of drinking water and damaging a pressurized gas main can fuel an explosion and fire large enough to destroy an entire neighborhood.

Ground Penetrating Radar

The most accurate method for locating underground facilities is Ground-Penetrating Radar; however, it is more involved and expensive than conventional mark-out techniques and its use is not required for utility mark-outs. While Ground-Penetrating Radar is not commonly used by Utilities for locating their facilities, it is a powerful tool that can be used by forward-thinking designers on projects in densely developed areas with extensive underground networks.

GPR can detect

  • Metallic & non-metallic pipes (PVC, Asbestos cement, Concrete storm and sewer systems)
  • Utilities with broken or damaged tracer wires
  • Underground storage tanks
  • Drainage tiles
  • Non-utility structures (Vaults, Foundation walls)

GPR complements traditional Electromagnetic (EM) Technology by:

  • Delineating utilities in close proximity
  • Providing reliable depth estimates
  • Allowing for data visualization to better map the subsurface
  • Reporting and archiving results for future reference
  • Integrating data with third-party software (eg. Google Earth)