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

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3.0 RENEWAL PRACTICES AND TECHNOLOGIES
This section covers current utility practices as well as a review of existing and emerging renewal
technologies for restoring structural and/or flow capacity to a distressed force main. As shown in
Figure 3-1, the renewal of force mains includes repair, rehabilitation, and replacement. The simplest form
of renewal is a spot repair, usually implemented on a reactive basis to a failure. More extensive renewal
technologies are rehabilitation (using the existing fabric of the force main pipe) and replacement
(installing an entirely new independent pipe). This new pipe can be installed offline using a different
line or online using the same line and grade of the existing pipe. Both offline and online replacement can
involve trenchless technologies.
Figure 3-1. Renewal Approaches for Force Mains
Current Utility Practices and Market
The estimate of renewal works in force mains are between 250,000 and 600,000 linear feet (76,220 and
182,927 meters) or 0.08% to 0.19% of the total length on an annual basis. While this is significantly
less than the proportion for gravity sewers, force mains are in general not as old as gravity sewers, so their
condition may be expected to be better in general.
At this time, both repair and replacement are more widely used than rehabilitation in force mains. Repair
can be undertaken within a short shutdown period, thus obviating the need for by-pass pumping. This is
often a simple patching of a damaged or deteriorated area. On the other hand, replacement requires a
major intervention. From the limited data available, it is estimated that replacement is the preferred
approach for most utilities when faced with force main problems. Replacement comprises between
200,000 and 500,000 linear feet (60,976 and 152,439 meters) of force mains annually or some 0.1% to
0.15% of the total length. There are no equivalent data on the frequency of repairs for force mains.
The current market for force main rehabilitation is small compared to repair and replacement. No
definitive data are available on the volume of force main rehabilitation since neither the utilities nor the
vendors report this information. The best estimate is that between 50,000 and 100,000 linear feet (15,244
and 30,488 meters) of force mains in the US are rehabilitated annually. This represents some 0.02% to
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