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

ferrous force mains is third-party damage, which accounts for 37% of failures. Corrosion and structural
failure together account for 54% of failures.
Renewal Technologies
Renewal of force mains includes repair, rehabilitation, and replacement. 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. 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. 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 0.03% of the overall
length. There are a variety of reasons for this lower rate of rehabilitation in sewer force mains. The first
is the lack of consistently reliable and cost-effective sewer force main inspection methods and the second
is the low number of rehabilitation technologies specific to force mains.
Force mains can operate with a wide range in pressures, from a few feet of head to hundreds, so there is
potentially a large number of technologies that can be adapted to force mains from other applications.
Vendors are constantly making improvements to their products so they should always be consulted before
using any of the identified technologies.
Repair
Repair of a failure or a deteriorated section of pipe is generally focused on only taking remedial action
with one or two sections of pipe. Oftentimes this work is done under emergency conditions. The first
objective is to prevent any further spill or damage to the environment and the second objective is to
restore service as quickly as possible. Repair can be broken down into open cut replacement of a
section(s) of pipe, spot repairs using cured-in-place-pipe (CIPP), mechanical sleeves or repair clamps, or
joint repairs using internal sleeves or external devices. Some examples of each are given in this report,
but repair is not a focus of this report.
Rehabilitation
In rehabilitation, the existing pipe becomes part of the renewal work. Rehabilitation methods will include
the use of spray-on linings, close-fit linings, CIPP, and woven hose lining systems. Technologies for
each of these rehabilitation categories are discussed in this report in addition to cleaning requirements
prior to rehabilitation. Because only limited rehabilitation work has been undertaken to date on sewer
force mains, many of the systems available were originally developed for water main rehabilitation, but
can be adapted to sewer force mains.
Spray-on linings have been one of the easiest methods of rehabilitating a pressurized main when the
primary objective is just to provide corrosion protection to the interior surface. Spray-on linings include
cementitious and polymer materials. Two polymers, epoxy and polyurethane, are used extensively in the
UK water industry to line water mains. Rapid cure time over cement mortar and resistance to soft water
have favored these materials. A new family of polymer spray-on linings, based on the use of polyurea, is
finding rapid acceptance for lining manholes, wetwells, and other structures exposed to corrosive
environments including pipes. One of the benefits of the use of polyurea is a very fast cure, with gel
times in 5 to 40 seconds. The liner can also be spray applied with a thickness up to 2 inches (50 mm).
This liner has the ability to serve as a semi-structural or structural liner and not just provide corrosion
protection.
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