Eating the Elephant One Bite at a Time - How an Effective Multi-Year CCTV and Assessment Program has Worked for the City of Chandler
Abstract:The City of Chandler Arizona (City) conducted a sewer system inspection pilot study in 2004 to assess the sewer system's current integrity. The majority of the system has been installed within the past 30 years. The pilot study showed significant deterioration of manholes and interceptors that was surprising for this relatively new system. Therefore, the City committed to a multi-year program of sewer assessments to protect the City's infrastructure investment and avoid the consequences of failures. The objective of the program was to inspect all sewer mains 15 inches and larger in diameter (approximately 100 miles), as well as the associated sewer manhole (approximately 1300). The project team completed four phases of the sewer assessment, resulting in evaluations of infrastructure condition and recommendations for rehabilitation.
The program utilized closed captioned television (CCTV) methods, which are widely used in the industry for sewer assessment. The City's GIS data was used to provide a common mapped system that the project team could use for coordination.
Nearly 92% of the pipelines equal to or greater than 15 inches in diameter and all associated manholes were inspected. Of these manholes roughly 22% needed repairs and about five miles of sewer interceptors needed repair. A condition rating was assigned to each inspected manhole and pipeline to indicate severity of the defects and the urgency of repairs. The team used this rating to prioritize repairs and to justify the funds needed for the repairs. This allows the City to manage the budget to complete the repairs.
The sewer assessment program benefitted Chandler in a number of important ways:
Identified infrastructure requiring emergency repair, thus avoiding catastrophic failure,
Identified at least five miles of interceptors needing repair,
Located at least 300 manholes needing repair,
Determined which construction methods/materials are not suitable for the harsh sewer environment,
Located and cleaned several areas with large accumulations of debris.
The City did not wait for a catastrophic failure or for regulatory constraints before implementing an inspection program. They chose instead to proactively maintain the collection system so that repairs could be handled earlier, and at a lower cost. This paper explains Chandler's sewer inspection program and summarizes the results of the inspections to date. Key components of a successful sewer inspection program are provided.
Document Type: Research Article
Publication date: 2010-01-01
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