State of Technology Report for Force Main Rehabilitation, Final ...

Gaps between what’s available versus what’s needed have also been identified in this report. Clearly the
biggest need would be for a fully structural liner that could be installed in a live sewer. Achieving that is
unlikely, at least in the next decade, but many other gaps are being closed. For example, vendors are
embarking on more long-term testing programs to help document the performance of their liners in a
pressurized system so that they can be designed for a minimum 50-year design life.
1.3 Project Approach
There are technologies that can be used in multiple applications. Sewer force mains have similar design
characteristics to water mains. Both must carry working and surge pressures of the system and are
generally buried only 4 to 8 feet (1.2 to 2.5 meters), so both are subjected to live loads in addition to
trench loads. Water mains carry potable water so their influence on water quality is important, which is
not the case with a sewer force main. However, the effluent carried in a force main is far more corrosive
than potable or raw water, especially where gas pockets develop, so a force main must have the same
corrosion resistant characteristics as a gravity sewer. Consequently, some technologies that are suitable
for sewer force mains, providing they also are certified to meet National Sanitation Foundation (NSF) 61,
would also be applicable for a water main. Also, some technologies that are used to line a gravity sewer
can also be used in a low pressure force main.
Recognizing that there would be some cross-over amongst the various technologies, a series of
technology-specific datasheets was created for each identified rehabilitation technology that is relevant to
sewer force mains. These technology profiles are included as Appendix A of this report. This
information was gathered by researching the technology (through published literature, Web sites, trade
shows, case studies, and magazine articles) and completing the technology-specific datasheet as much as
possible with publicly-available information. Each datasheet was then sent to the vendor to review and
comment on the contents and to provide additional information as needed. As discussed in Section 4, an
effort was made to collect representative cost information, but often only limited cost data were available.
1.4 Organization of Report
The report is organized according to the following subjects:
• Section 1: Introduction – project background
• Section 2: Characteristics of Force Main Systems – materials used, diameters and age
distribution, and typical failure modes and mechanisms
• Section 3: Renewal Practices and Technologies – current utility practices and renewal market
including an overview of repair, rehabilitation, and replacement technologies applicable to
force mains
• Section 4: Technology Selection Considerations – life-cycle costs, capacity limitations,
accessibility, maintenance, asset condition, and asset criticality are all factors to consider in
the selection of the most appropriate renewal strategy
• Section 5: Design and Quality Assurance/Quality Control – system design and renewal
design, product and installation standards, design standards, short-term and long-term testing
requirements, and field QA/QC practices
• Section 6: Operation and Maintenance – procedures to prolong the life of a force main,
including cleaning, cathodic protection, monitoring, and other maintenance considerations
• Section 7: Gaps Between Needs and Available Technologies – data and capability gaps, key
parameters for evaluation in demonstration project
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