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Case Study

Foothill Municipal Water District

The Foothill Municipal Water District (FMWD) serves approximately 86,000 people through its member agencies located in the foothills of the San Gabriel Mountains, bordered between the City of Pasadena and the City of Glendale. In March 2013, Pure Technologies (Pure) successfully completed in La Canada Flintridge, a 2.2-mile internal inspection and condition assessment of a 24-inch mortar-lined steel force main to identify broad areas of wall loss.

Project Details

Services
PureRobotics™ electromagnetic condition assessment inspection

PureRobotics HD-CCTV inspection

Structural assessment

Engineering services

Risk prioritization

Timing
2013
Pipe Material
Mortar-lined Steel
Inspection Length
2.2 miles (3.55 km)
Diameter
24-inch (610-mm)
Transmission Type
Water

Project Highlights

EM data identified 17 anomalies warranting further investigation

FMWD selected 2 locations to perform test pitting

Results revealed minimal wall loss and continued operation of water main

Challenge

For utilities like 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.

As well, 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 has helped FMWD determine where to focus more detailed inspections in order to make detailed rehabilitation decisions for this force main.

Solution

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

The robotics tool used was assembled inside the pipeline and controlled remotely by operators on ground level. This allowed FMWD to maximize the HD-CCTV function as internal features could be closely inspected with the camera. By opting for an inline assessment in favor of traditional metallic inspection methods, FMWD has a baseline condition of the entire 2.2-mile water main.

Results

After reviewing the electromagnetic data, Pure Technologies was able to identify 17 electromagnetic anomalies that warrant additional investigation. Using the resulting information, the top 10 anomalies were ranked based on the strength, area and repeatability of signal loss and visually using HD-CCTV.

FMWD selected two 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.

Results of the two test pits revealed minimal wall loss and resulted in the continued operation of the steel water main with no rehabilitation required. Ranking the anomalies based on size allowed the prioritization of further inspection based on sound and defensible engineering judgment.

Risk prioritization is an important facet of any condition assessment program because it allows the most urgent needs to be addressed first. By proactively managing its pipeline assets, FMWD is able to continue to deliver quality water to its member agencies in a cost-efficient manner to meet their projected demands.