Foothill Municipal Water District Assesses Mortar Lined Steel Pipe

For utilities like Foothill Municipal Water District (FMWD), which has no redundancy in its system, finding a reliable inspection method that provides condition data for the entire length of a steel pipeline is an important aspect of its condition assessment program.

FMWD covers about 22 square miles in the foothills of the San Gabriel Mountains, bordered between the City of Pasadena on the east and the City of Glendale on the south and west. The District serves approximately 86,000 people through its own member agencies.

In March 2013, FMWD successfully completed a 2.2-mile internal inspection and condition assessment of a 24-inch mortar-lined steel main to identify broad areas of wall loss. As part of the condition assessment, a structural evaluation was performed to determine whether the force main design satisfies AWWA M11 “Steel Pipe – A Guide for Design and Installation,” fourth edition standards. The results of this evaluation will help FMWD determine where to focus more detailed inspections in order to make detailed rehabilitation decisions for this force main.

To complete the inspection, FMWD used PureRobotics™ electromagnetic condition assessment equipped with PureEM™ technology and high-definition closed circuit television (HD-CCTV). The platform is a non-destructive, inline assessment tool that provides screening level wall data in the circumferential and axial directions of metallic pipelines.

By opting for an inline assessment in favor of traditional metallic inspection methods, FMWD has a baseline condition of the entire 2.2-mile main. After reviewing the EM data, FMWD was able to identify 17 EM anomalies that warrant additional investigation. The top 10 anomalies have been ranked based on the strength, area and repeatability of signal loss and visually using HD-CCTV. FMWD can now select the most appropriate locations to perform test pitting to obtain higher resolution data needed to evaluate rehabilitation or repair needs and determine the remaining useful life of the water main.

PureNET Overhead

FMWD inserts the PureRobotics tool for inspection.

Field Data Collection

During inspection, the tool remains tethered to the service and is controlled by an operator.

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