Thousand Oaks installs 50-year HOBAS pipe

A Southern California master-planned community has installed 50-year HOBAS pipe to repair a sewer line carrying two-thirds of the city's flow.

Feb. 26, 2004 -- Thousand Oaks is a Southern California master-planned community. It is 12 miles from the Pacific Ocean and boasts of a beautiful landscape and a clear view. Under it all is an infrastructure that is maintained in a way that could be an example for many other municipalities.

When a sewer line carrying two-thirds of the city's flow needed repair, HOBAS pipe was chosen as part of the solution because of its projected long operational life. The new line replaced an older 36-inch reinforced concrete pipe that was exposed in several areas. Boulders and rocks tumbling off the canyon wall also damaged the existing line.

The new Unit "W" Trunk Sewer replacement, Phase II, utilized abrasion resistant HOBAS pipe. The new line traversed some rugged country. It was installed under a creek bed in the middle of a steep canyon that dropped more than 140 vertical feet from end to end of the 5,000-foot long pipeline.

Never-ending Mission

The City of Thousand Oaks maintains more than 500 miles of wastewater pipeline. Their collection system has an excellent operational and environmental record. Construction is ongoing to improve the collection system along with treatment plant capacity and reliability in order to minimize the possibility of system overflows, decrease liability exposure and simultaneously improve effluent quality and protect the environment.

Meeting new and more stringent environmental standards and regulations is a never-ending challenge and ongoing mission of the Thousand Oaks professional wastewater system staff.

HOBAS Chosen

Several pipe alternatives were specified on the project including PVC lined reinforced concrete pipe, polyurethane lined ductile iron, solid wall polyethylene and HOBAS. The 30-, 36- and 48-inch diameter, 46-psi pipe stiffness HOBAS pipe was specified for the wastewater line to add increased competition on the project. The HOBAS product was ultimately chosen by the contractor to be installed through this winding canyon.

50-Year Pipe

Some of the design considerations for this challenging installation were the long-term corrosion resistance and the durability of the product.

"We are confident the installation resulted in a good 50-year pipe," said John Turner, P.E .of Boyle Engineering Corporation of Ventura, Calif., design engineer for the pipeline. Although Turner had heard of HOBAS, he had never actually specified the product before. With the installation now complete, he states that he would specify and use the product again, especially for larger diameter trunk lines.

The City of Thousand Oaks, the owner of the line, also has faith in the long-term performance of the pipe and Shamir Shahamiri, project manager for the city, said "The project went well; we are optimistic for many years of service." He added that he believed this pipe will last until his retirement.

Tough Canyon Installation

Although the contractor, ASI Civil of Carlsbad, Calif., had many options to choose from, they utilized HOBAS because of the handling and workability advantages that would make it easier to install in the constraints of the canyon. The HOBAS pipe was lighter and easier to handle than the concrete option. It did not require add-on linings and coatings, which could be damaged. The HOBAS was easily joined with push together joints eliminating the need for on-site heat fusion that would be necessary for the solid wall polyethylene pipe.

Custom Fittings

The complex installation included many factory-made mitered elbows and several bends that the contractor accomplished in the field by offsetting joints. HOBAS provided custom elbows to meet the specific project criteria. Special angles not available from most pipe manufacturers and versatile fitting fabrication were supplied at the same cost as standard fitting angles. The HOBAS custom fitting shop can easily provide this service on most projects. Short pipe segments were also utilized to maneuver radius curves.

Testing Complete

As the project progressed, each reach was pressure tested by surcharging the line and no problems were found. The project is now complete and in service.

About HOBAS Pipe

HOBAS pipe is manufactured in sizes from 18 inches to 110 inches in pressure and non-pressure classes. For more information, please contact HOBAS at 800-856-7473, 281-821-2200 or e-mail at Facts are also available at

More in Distribution