Installation of the PRB is typically monitored during injections by the active resistivity method to map its geometrical extent and ensure inclusion coalescence or overlap between adjacent wells. This monitoring program qualitatively verifies that the reactive barrier is installed with no gaps or voids.
During injections, the gel-iron mixture is energized by a 100Hz low voltage source and adjacent resistivity receivers are monitored to detect changes in induced voltages by the propagation of the carrier fluid. From these induced voltages and utilizing an incremental inverse integral method, the inclusion geometry is displayed in real time during the installation process.
The first commercial application of this technology was for a PRB installation in 1997. Since then GeoSierra Environmental’s real-time imaging technology has been used for most GeoSierra Environmental’s installations to ensure each PRB is constructed as planned according to quality assurance specification requirements. Recently, advances in imaging have been made during PRB installations near overhead power lines.