Underground Construction - October 2019 - 27

The first rehabilitation technique
focused on water quality and hydraulic
issues associated with unlined cast iron
pipe. Unlined cast and ductile iron pipe
remained common until the early 1970s.
Cement mortar lining (CML) was
implemented in Australia in trowel-on
applications as early as 1905. It gained
widespread use in 1934, when it introduced
as a spray-on application in New Jersey.
CML remains the most common nonstructural spray lining technique utilized in
pressure pipe to this day.
The next generation of technologies
involved the advent of spray-on polymeric
systems. Spray-on epoxies were first trialed
in the UK during the 1970s, where virtually
tens of thousands of miles have been
relined. Polymeric linings evolved further
in the last couple of decades to include
the use of rapid-setting polyurethanes
and polyurea hybrids. As these systems
evolved, it became understood that they
actually added structural enhancement to
the host pipe, in addition to the benefits
of improved hydraulics and water quality.
Rapid-setting polymers also allowed for a
same-day return to service, which changed
the dynamics of program implementation.
Sliplining, the oldest form of fully structural rehabilitation, started in the 1940s.
The development of polyethylene pipe in
the 1950s greatly enhanced the technical
feasibility of sliplining and increased its use.
Conventional sliplining inherently results
in a large reduction in diameter. In the
1980s and throughout the 1990s this led
to the development of a wide range of variations of sliplining techniques, including
close-fit liners whereby the cross section of
the liner is temporarily reduced, deformed
or folded to accommodate insertion into
the host pipe and minimize the diameter
reduction seen with conventional sliplining.
Pipe bursting utilizes same path
technology by fracturing, splitting or
bursting the existing pipe while pulling in
new pipe through the existing path. While
pipe bursting provides for full structural
rehabilitation, it also allows for upsizing
the diameter to accommodate the need for
additional capacity.
Cured-in-Place Pipe (CIPP) was first
introduced for gravity sewer applications in
1971. Lower pressure applications, such as
sewage force mains, were routinely relined
in the 1980s and the inaugural edition of
ASTM F1216 in 1989 had pressure pipe

Water Main Rehabilitation with Reinforced CIPP. Courtesy of HammerHead Trenchless

design considerations in Appendix X1.
However, it wasn't until 1998 that a fully
structural reinforced pressure pipe CIPP
was developed and used to rehabilitate
pressurized water service pipelines at the
Perry Nuclear Plant in Cleveland, Ohio. The
advent of reinforced CIPP liners greatly
expanded the use of CIPP as an alternative
to conventional replacement, due to its
reduced construction footprint and the
potential to reduce capital and life cycle cost.
Montreal's program started in 1999, was
ramped up markedly in 2008, and routinely
does 35,000 to 40,000 feet annually. Since
the city of Toronto started its dedicated
CIPP Fully Structural Relining Program in
2008, it has grown to a $55-million annual
program attempting to rehabilitate some
200,000 feet of water main annually.

Industry Standards
The rehabilitation "toolbox" has increased
considerably since someone first handtroweled cement mortar on the inside
of an iron pipe in 1905. A wide range of
rehabilitation needs have been identified
and a wide range of solutions have been
developed and continue to evolve. In North
America and worldwide, the framework
for matching problems to technology owes
a lot to the development of a Structural
Classification System for water main
rehabilitation systems.
The concept of a Structural Classification
System for lining technologies for pressure
pipes dates back to late 1990s' work by Drs.
Jesse Boot, John Heavens and John Gumbel,
in the United Kingdom. It was introduced
in North America in the Second Edition of
AWWA Manual M28, Rehabilitation of Water
Mains, published in 2001, and in the UK
under BS EN 13689: "Guidance on the classification and design of plastics piping systems used
for renovation" in 2002.
The concept developed was a qualitative
one, based on intended function of the
lining technology, its degree of interaction

with the host pipe, and the type of loads
the lining was intended to resist. While
the qualitative framework has served
the industry well to match rehabilitation
solutions to known water main problems
or deterioration modes, there is a large gap
between "qualitative" and "quantitative"
objectives, as the industry put the classification system into actual practice.
Development of industry standards is
a work in progress, with an objective of
providing common language and guidelines
for the assessment and use of pressure pipe
rehabilitation technologies in organizations like AWWA and NASSCO. Through
these standards, critical installed material
properties and values are defined, along
with repeatable testing for product compliance and installed acceptance.
NASSCO addresses pressure pipe rehabilitation issues through its Pressure Pipe
Committee. This select group of industry
professionals is responsible for researching
current pressure pipe assessment and rehabilitation processes, with a goal to establish
standards to assess and rehabilitate force
mains and water lines.
The pressure pipe rehabilitation market
is evolving and growing at a fast rate. Well
over a million miles of drinking water pipe
are in service in North America, with much
of it operating beyond its intended design
life. Nearly 6 billion gallons of treated
drinking water are lost every day (or over
2 trillion gallons per year) through leaking
pipes and breaks.
In order to meet demands, AWWA
estimates that $1 trillion of investments
in water infrastructure is needed over the
next 25 years alone. Increased acceptance
and utilization of viable trenchless technology solutions, research and standards in a
proactive approach will help reduce break
frequencies, improve water quality, save
energy in the transport of water, as well as
close the funding gap. *
UConOnline.com | OCTOBER 2019

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Underground Construction - October 2019

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