Underground Construction - August 2020 - 15

What Users Say About Clay Pipe
Engineering
In New York City, vitrified clay pipe (VCP) is specified for all sewers (storm, sanitary and combined) that
are 18 inches or less in diameter, said George Cowan, P.E., former assistant commissioner-Infrastructure Division, New York City Department of Design and Construction.
"Current specifications," he added. "only permit the cut and cover method for clay pipe, although
other methods such as the pilot tube method, have been used due to circumstances and certain
restriction.
"I do not personally know of any issues during cleaning the clay pipe.
"Based upon my 50 years in sewer construction and maintenance, I believe clay to be the best
choice due to its performance over time," Cowan added.

Municipality
In California, Chad Rocha of the Morro Bay Division, city of Morro Bay, reports that about 65 percent
of the city's sanitary sewer system is vitrified clay pipe, most of it 6 inches in diameter.
He believes VCP's ability to withstand high-pressure water for cleaning purposes is an important
benefit of clay pipe.

Contractor
Grbcon Inc. is a contractor specializing in sewer and storm drain pipeline construction in Southern
California.
Vice President John W. Gavigan says Grbcon uses open-cut construction to remove and replace
old pipe with VCP.
"In heavily populated urban areas with numerous other utilities in the public right-of-way," Gavigan
explained, "shorter lengths of VCP make it easier to install near conflicting utilities. VCP also is a better
host pipe if an agency decides to rehabilitate its mainline pipe with CIPP sometime in the future." *

sanitary sewer systems, he claims.
"VCP is a fired ceramic and is the only
pipe that will not deteriorate over time in
a sanitary sewer environment," Boschert
said. "Plastics lose strength as they age,
and concrete and iron pipes are susceptible
to corrosion from the hydrogen sulfide
present in sewer pipes. The physical properties of clay pipe, however, never change,
providing the longest service life of any
pipe material available."

Composition
Clay pipe products are made from various
types of shale and clay, which are the
natural decomposition product of stone. It
is an abundant, naturally occurring group
of materials found all over the country. All
that is added is a little water.

Compression and heat are applied to
the raw materials to convert them into
a chemically inert ceramic. There is zero
waste generated in the process and total
embodied energy is roughly half that of
manufacturing other sewer pipe materials.
"Vitrified clay pipe is as close to
permanent as any material can be for
gravity sewer applications," Boschert
pointed out. "Due to VCP's long life cycle,
and the fact that it is chemically inert and
does not change over time, there are no
long-term disposal or decay concerns."
Boschert reports that VCP has a
9 rating on the Mohs hardness scale
and an average compressive strength
of 18,000 pounds per square inch.
All common methods of cleaning sewer
lines can be safely used in VCP sewer
pipe including hydro-mechanical tooling,
hydro-flush nozzles, mechanical rodding,
bucketing and chain/cable type cutters.
These aggressive cleaning methods have
been instrumental in successful programs
to reduce SSOs.

Open cut and trenchless
VCP is available in diameters from 4 to
42 inches for open-cut construction.
"The open-cut bell/spigot and plain-

A clay pipe open-cut project from 1924 in
Shreveport, La.

end pipe market has the lion's share
(95 percent) of VCP supplied," Boschert
said. "Trenchless installations with clay
jacking pipe have significantly smaller
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