HGI has developed an extensive base of relevant project experience in performing studies locating buried pipelines in various environments. The method used can vary based on the target size and depth, the soil chemistry, site conditions and other parameters. Commonly Ground Penetrating Radar (GPR) and the Geophysical Operations (G.O.) Cart are utilized.
Ground Penetrating Radar
Ground penetrating radar (GPR) is typically used as a characterization tool in conditions where there is abundant surface or near-surface metallic infrastructure such as fences, pipes, buried debris piles etc. GPR is capable of locating metallic and non-metallic subsurface infrastructure. GPR surveys are conducted using a Noggin Smart Cart system (Sensors and Software, Mississauga, ON), which includes a GPR system (transmitting and receiving antennae, battery, and energy source) and digital output display, both housed on a fiberglass cart. The Smart Cart is usually outfitted with a Leica 1200 RTK GPS unit (Leica Geosystems AG, Heerbrugg, Switzerland) for geo-referencing of data and a heads-up display/GPS light bar (Ag Leader Technology, Ames, IA) to allow real-time navigation while traversing the survey area.
An example where HGI commonly uses GPR is at the Hanford Site in SE Washington for its Surface Geophysical Exploration (SGE) program. This nuclear facility has numerous tank farms, creating a complex environment for characterization studies due to the amount of buried infrastructure. Below are the results from a GPR survey performed inside a tank farm (241-TX Farm). In this scenario GPR can image pipelines to a depth of approximately 10 feet to clear areas before excavation commences.
Geophysical Operations Cart (G.O. Cart™)
The Geophysical Operations (G.O. Cart™) is a non-magnetic, non-metallic platform that is equipped with both Electromagnetic (EM) and Magnetic sensors and can be towed behind a vehicle. These two instruments complement each other as each method measures different physical property contrasts. The G.O. Cart™ can be used to cover large areas quickly while performing a site clearance survey.
The G.O Cart™ is best utilized in open areas with minimal surface obstructions. This method is commonly used at the Hanford Site to survey large waste sites before an excavation begins. This method has proven to be very beneficial based on the speed and ease of collection, and the accuracy of the results based on the electromagnetic and magnetic sensors collecting data concurrently. Below is an example of the Electromagnetic results from a G.O. Cart survey surrounding a tank farm environment.