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Protecting Philadelphia's 3,000 – Mile Sewer Investment

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The Philadelphia Water Department (PWD), with technical assistance from Hazen and Sawyer P.C., developed a substantive Sewer Assessment Program (SAP) that standardized sewer TV inspections and developed a systematic and consistent methodology for assessing and prioritizing sewer rehabilitation and sewer maintenance needs of Philadelphia's 3,000 miles sewer collection system. Procedures, protocols, assessment and ranking of sewer by severity were tested and validated through a three-year pilot program that included approximately 7% of the City's sewer collection system. Continuous feedback from PWD enhanced and customized the SAP for integration with PWD's GIS system that is currently under development.

The cornerstone of the SAP is the accurate standardized documentation of observations and defects by closed circuit TV inspection. To assure reporting accuracy, a comprehensive classroom and field training program for TV operators, maintenance personnel and engineering staff was developed and implemented, utilizing the Pipeline Assessment and Certification Program customized for PWD. Sewer inspection information, still pictures and video snippets were captured electronically using the WinCan TV inspection module tailored for PWD. Quality control and quality assurance procedures were established and meticulously followed for review and correction of sewer inspection data and reports. Procedures for data transfer were developed and implemented programmatically to assure that data not conforming to the inspection protocols were identified and corrected before been uploaded to PWD's server.

Algorithms, for data analysis, were developed considering different priorities given by PWD to different type of defects. Defect levels ranging from 1-5 were assigned to individual defects based on severity. Appropriately weighted “defect multipliers” ranging form 1 to 500 for localized structural defects were applied to adjust defect levels. Defect levels for continuous defects, defects extending over a length of sewer, were adjusted with defects multipliers ranging from 10-2,250. Individual structural defect scores were then summed up to provide a segment score and consequently segment scores were summed up to provide a score on per block basis. Block scores were adjusted with “Modifiers” accounting for out-of sewer factors such as location, sewer characteristics, depth and hydraulic adequacy. Blocks with the highest scores and consequently greatest needs are addressed first.

Document Type: Research Article


Publication date: 2005-01-01

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