Optimistic for Years of Service

Dec. 9, 2003
California city puts sewer line problem out of site, mind

Hobas Pipe USA, Inc.

1413 Richey Road * Houston, TX 77073-3508

Phone 800/856-7473


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 pipe.

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 product.

“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 trunk lines.

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.

Custom fittings

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.

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