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Technology Report Released For Force Main Rehab
Editor’s Note: A U.S. Environmental Protection Agency (EPA) report published earlier this year contains a wealth of information about rehabilitation technologies available for sewer force mains. The report, “State of Technology Report for Force Main Rehabilitation,” was prepared as part of the EPA’s Sustainable Water Infrastructure Initiative. Under this program, research is being conducted to improve and evaluate innovative technologies that can reduce costs and increase the effectiveness of the operation, maintenance and renewal of aging drinking water distribution and wastewater conveyance systems (EPA, 2007). Robert S. Morrison, P.E., Jason Consultants LLC, was a principal author of the report, and below is his summary of its contents.
The main portion of the report is a review of all known technologies that could be utilized in the rehabilitation of sewer force mains. It includes discussions of currently used technologies, as well as potential cross-over technologies previously used to rehabilitate water mains and gravity sewers, with technology-specific data sheets included in the appendices.
The sewer force main system in the United States is comprised of approximately 60,000 miles of pipe. Only two percent of the force mains have been in service for over 50 years, making the force main network relatively young compared to the water network where nearly half are over 50 years old. However, force mains, especially large-diameter ones, tend to be more critical as the consequence of failure can be significant. Given the aggressive nature of the effluent, and that over 30 percent of force mains are at least 25 years of age, failures are starting to increase in frequency.
For ferrous pipes, which represents over 63 percent of all force mains, internal corrosion is the leading cause of failure at 26 percent, followed by third-party damage at 19.4 percent and external corrosion at 19.2 percent. Corrosion and structural failure together account for 54 percent of failures.
The report discusses the various renewal practices and technologies available, focusing on rehabilitation and replacement, and briefly touching on repair options (which are not the focus of the report).