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Large-Diameter Sewer Condition Assessment: Columbus' Program Development and Early Cost-Saving Results

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In 2002, the City of Columbus, Ohio and the State of Ohio entered into a consent order agreement requiring Columbus to “develop and implement a program to address the capacity, management, and operation and maintenance of its sewer system. ” One condition of that CMOM-oriented consent order requires the City to “conduct routine preventive operation and maintenance activities for its sewers” to minimize overflows and basement backups. Columbus owns and operates over 3,100 miles of sanitary sewers, of which 165 miles are classified as “large diameter sanitary sewers” with diameters greater than 36 inches. For these large diameter sewers, Columbus subcontracts any associated inspection and rehabilitation work, while smaller diameter sewers are maintained by City staff.

Prior to consent order issuance, no formal large diameter sewer cleaning and inspection program existed for the sole purpose of preventive maintenance. Virtually all cleaning and inspection of these larger pipes was part of pipe rehabilitation projects. Inspections were limited in scope to provide enough information for subsequent rehabilitation-related capital improvements, but the data was not further analyzed to develop optimized preventive maintenance activities. In response to the CMOM program, the City recognized the need to acquire condition data in order to better maintain its collection system assets.

In October 2005 Brown and Caldwell and the City of Columbus (City) worked together to focus on how best to establish a programmatic approach to large-diameter sewer preventive maintenance. With the help of Brown and Caldwell, the City determined the best way to prioritize and package contiguous sections of pipe into manageable and affordable projects that could be contracted out to vendors specializing in large-diameter pipe inspection activities. This initial method was mapped out in the 2006 Large Diameter Pipe Program Condition Assessment and Cleaning Prioritization report. It included details about the methodology and ultimately provided a recommended sequence for a series of sewer inspection tasks.

This paper focuses on the first in the series of large-diameter sewer inspection projects - the Olentangy Main Trunk Sewer Condition Assessment Project - performed by the City's Division of Sewerage and Drainage with the assistance of Brown and Caldwell. We will cover three key areas of the process:

General project introduction and project origins,

Project methodology, and

Lessons learned.

Keywords: Asset Management; CCTV; CMOM; Condition Assessment; Large Diameter Sewer; Preventive Maintenance; Prioritization; Risk; Sewer Inspection Techniques; Sonar

Document Type: Research Article


Publication date: 2009-01-01

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