May 2018 Vol 73 No. 5


Arcadis Provides ‘Living’ Software Presentation to Assess Interceptor Condition, Risk

At the April 4 meeting of the Gulf Coast Chapter of the Underground Construction Technology Association, Harrison Steed, P.E., senior project manager with Arcadis, discussed  a complex project involving Dallas Water Utilities’ wastewater collection system. Spanning more  than 230 miles of large-diameter (24 inches and greater) interceptors, pipe in the system dated back to the early 1900s.

“Due to the aging infrastructure and the need for reliable capital improvement program (CIP) planning, DWU was seeking a way to effectively prioritize rehabilitation and replacement projects for both the present and the future,” said Steed. “Arcadis was retained to assess the interceptor system condition and risk.”

For the condition assessment, Arcadis used several inspection technologies and NASSCO’s PACP chart to look at 100 miles of the total. That’s when the project became even more complicated.

“Trending didn’t show the pattern DWU hoped for,” said Steed. “Actually, the first results were not as bad as everyone thought they would be.”

That was due to accessibility problems, including location constraints and technological limitations. “Even with sophisticated technology, there were stretches we couldn’t physically inspect.

“In the absence of that inspection data, we used statistical probability models to leverage the condition of inspected pipes to forecast condition of inaccessible pipes within the interceptor system.”

This data was combined with performance condition data and spatial consequence of failure in order to determine the risk for each pipe segment. “In other words, how expensive and painful would failure be in each case,” he added.
Arcadis then used its Rehabilitation and Replacement Planning System (RRPS), a software tool designed for distributed assets managed with a geographic information system (GIS)-based tool. to assist in the selection of CIP projects and overall reduction of system risk. RRPS is RRPS is used to identify the high-risk assets based on the physical inspection data for renewal or replacement.

The tool also has a “living and breathing” aspect, said Steed. “After giving them a basis for why and how to spend the money they had, we showed DWU how to run RRPS themselves going forward to recalculate the condition assessment with updated data.”

Harrison Steed is a civil engineer with 16 years of experience in large-diameter water and wastewater municipal pipeline planning, condition assessment, design and rehabilitation. He has worked on more than 50 different sewer projects, from 8- to 120-inch diameter, totaling 1.5 million feet.

UCTA Gulf Coast, (713) 830-2184,

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