The City of Las Vegas has joined other large urban areas in the move toward rehabilitation of its aging infrastructure. Recently the city renewed its Sloan Lane Interceptor — a renovation utilizing more than 12,500 ft. of 40-in., 45-in. and 51-in. Hobas centrifugally cast fiberglass reinforced polymer mortar (CCFRPM) pipe to slipline the deteriorating reinforced concrete pipe (RCP) host.
The Sloan Lane line originally was built as a storm sewer
and later was converted to sanitary use. That meant these RCP pipes needed
renewal to provide corrosion protection against sulfide-caused deterioration
and to upgrade the joints to prevent infiltration.
Since the existing pipes were buried at very shallow depths
with only 1 to 8 feet of cover, both an open cut replacement and a lining
option were included in the bid specifications.
The replacement alternative allowed three pipe materials:
reinforced concrete with 360 degree PVC lining, profile wall PVC and CCFRPM,
all in diameters 42-in., 48-in. and 54-in. For the lining option, the specs
included cured-in-place pipe (CIPP) or sliplining with CCFRPM pipe. The
existing pipes were located in streets and the specs required new manholes at
800-ft. to 1000-ft. spacing, regardless of the construction method and product
that were selected.
The winning bid of Barnard Construction of Bozeman, Mont.,
was based on sliplining with Hobas CCFRPM pipe. Typically, the shallow depths
would favor open cut installation, but in this case, sliplining turned out to
be slightly less expensive, primarily because of the in-street alignment.
First, this rehab method eliminated the need to tear up the streets to replace
the existing line. Second, sliplining cost was lower because the CCFRPM pipe
could be installed under live flow conditions, eliminating the by-pass pumping
that would have been required for CIPP.
Even though the
sliplining reduced inside diameters by approximately 10 percent, the flow
capacity of the renovated line was actually increased slightly because of the
positive hydraulic characteristics of the Hobas CCFRPM pipes.
To facilitate the sliplining insertion, Hobas delivered the
CCFRPM pipe with flush, gasket-sealed, bell-spigot joints to maximize the
clearance at one to 11/2 in.
radially. Because of the shallow cover depth and the limited drive distances
between the new manholes, Barnard used a backhoe to push the pipes. Even with
half-full sewage flow conditions, 1,000-ft. runs were completed in half a day.
Grouting of the annulus in one lift, using a 42 pcf mix,
completed the installation. With no leaks and no pipe breaks, the project was
termed, “ho hum” by Barnard’s crew because of the lack of
problems. All of the parties involved were so pleased that Barnard is using
Hobas Pipe again in tunnels in Lubbock, Texas and the City of Las Vegas is
installing two miles of 42-in. and 60-in. Hobas jacking pipe on the U.S. 95
Rancho sewer project.
Hobas Pipe is manufactured in sizes from 18 in. to 102 in.
in pressure and non-pressure classes.
For additional information, contact Hobas at 800-856-7473.
RSS: Roads & Bridges Articles
