CPM was contracted to perform a condition assessment inspection along two sections of 8-inch ductile iron pipe (DIP) waste activated sludge lines located in Arizona. CPM utilized an Electromagnetic Bracelet Probe^™ (BP) and an Ultrasonic Thickness (UT) gauge to collect pipe wall thickness data at the exposed segments of pipe.

Metallic wastewater pipelines such as DIP experience corrosion and pipe wall loss due to exposure to hydrogen sulfide and other caustic gases common in wastewater pipes. Generally, this deterioration is focused along the top portion of the pipeline though corrosion can be found across the entire diameter.

CPM was made aware that previous inspetion efforts had been performed along the pipeline segments including closed circuit television (CCTV) video recording and analysis. The locations where the BP scans and UT readings were performed were chosen due to their proximity to air release valves (ARVs). ARVs are typically placed at high points where gas accumulates, and as noted, the gases associated with wastewater pipelines can severely expedite corrosion. Therefore, the inspection locations were estimated to have greater than average levels of corrosion and pipe wall loss.

The pipeline was excavated and exposed at each location, providing the necessary space to perform the BP scans properly. While both sections were buried beneath pavement, location one was located at the dead-end of a low-traffic roadway while location two required traffic control as it was near a busy intersection. Both inspections were completed at night in order to minimize safety risks.