Fort Worth Launches Unique, Aggressive Sewer Inspection/Cleaning Program

By Jeff Griffin, Senior Editor | July 2011, Vol. 66 No. 7

Program management
Gadberry said the third and most important facet of the ICAP is program management. All information gathered is assembled into a mosaic image of the system’s sewer interceptors for analysis of the data and to use in making recommendations, including an estimate of the remaining useful life of each pipe.

White Rock Consultants and sub-consultant Freese Nichols Inc. were selected to manage the project.

In order to take full advantage of this technology, specific information is needed. Pipe material, wall thickness and location of steel placement is critical and should be made available prior to post processing the field data. Once the 3-D rendering has been completed, the dataset will contain accurate measurements of wall loss due to deterioration and/or corrosion.

“Laser data is used to measure and visualize the inside profile of the pipe,” said Rod Thornhill, president of White Rock Consultants. “This identifies pipes with wall loss from corrosion, pipes that are out of round (deflection or deformation), and measures the true inside diameter of the pipe. The sonar measures and profiles the amount of debris below the water flowline and is the primary tool used to select pipes for follow-up cleaning.”

FWWD utilizes a pipe television inspection software application from Infrastructure Technologies (IT). Under the ICAP program, a conversion application was developed to merge the 3-D laser, sonar and HDTV data, videos, pictures and observations into the existing inspection database. All the pipe material and hydraulic model data is pre-populated into each inspection record using the IT pipe GIS SendIT module. The modeled wet/dry weather average depth and wet/dry weather maximum depth are incorporated into the dataset for evaluation during the review process.

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The typical deliverable of a 3-D laser, sonar and HDTV inspection is a printed PDF report. However, Gadberry said the FWWD has elected to maintain the inspection records digitally which allows multiple inspections of a single asset to be compared over time.

“The ability to compare pipe wall deterioration over the years will be extremely valuable when estimating the remaining useful life of our assets,” he explained

Thornhill said one interesting aspect of the project was that early inspection data identified many pipe sections where the dry weather flow significantly differed from the dry weather flow predicted by the model.