Optimistic for Years of Service
California city puts sewer line problem out of site, mind
Hobas Pipe USA, Inc.
1413 Richey Road * Houston, TX 77073-3508
When a sewer line carrying 2/3 of the flow from the
city of Thousand Oaks, Calif., was in need of repair, Hobas Pipe USA, Inc., was
chosen as part of the solution.
A new sewer line was slated to replace an older 36-in.
reinforced concrete line that was exposed in several areas. In addition to the
standard elements and conditions that affected the interior and exterior of the
concrete line, boulders and rocks that tumbled from a canyon wall also damaged
the exterior existing line. The new Unit “W” Trunk Sewer
replacement project, Phase II eventually incorporated abrasion resistant Hobas
The line traversed some rugged country calling for
installation under a creek bed in the middle of a sloped canyon that dropped
more than 140 vertical feet throughout the 5,000-ft pipeline length.
Several pipe alternatives were specified on the project
including PVC-lined reinforced concrete pipe; polyurethane-lined ductile iron pipe;
solid wall polyethylene; and the Hobas manufactured pipe. The 30-, 36- and
48-in.-diameter, 46 psi pipe stiffness Hobas pipes were specified for the
wastewater line, adding increased competition to the project. The product
ultimately chosen by the contractor to be installed throughout this winding
canyon installation was a Hobas product.
Some of the design considerations for this challenging
installation were the long-term corrosion resistance and the durability of the
“We were confident the installation resulted in a good
50 year pipe,” said John Turner, P.E., for Boyle Engineering Corp.,
design engineer for the project.
Although Turner had heard of Hobas he had never actually
specified the product before. With the installation now complete, Turner stated
that he would specify and use the product again, especially for larger diameter
The city of Thousand Oaks also had faith in the long-term
performance of the pipe.
According to city officials, the installation went well and
they, too, are optimistic for many years of service.
While the contractor, ASI Civil of Carlsbad, Calif., had
many options to choose from, they utilized the Hobas pipe due to the handling
and workability advantages in the constraints of the canyon. This pipe was
lighter and easier to handle than the concrete option. It did not require
add-on linings and coatings, which could eventually be damaged, and the pipe
was easily joined with push together joints rather than using onsite heat
fusion, which is necessary for the solid wall polyethylene pipe.
This complex installation included many factory-made mitered
elbows, and several bends, which were installed by the contractor in the field
by offsetting joints. Hobas provided custom elbows to meet the project specific
criteria. Special angles not available from most pipe manufacturers and
versatility fitting fabrication were customized at no additional cost over
standard fitting angles by the manufacturer. Short pipe segments were also
utilized to maneuver radius curves.
As the project progressed, each reach was pressure tested by
surcharging the line without any problems.