Compound Curve Microtunnel Drive Completed for SARI Project in Southern California

Orange County Public Works Department recently passed another milestone on the Santa Ana River Interceptor (SARI) Relocation – SARI Mainline project. James W. Fowler Co., the microtunneling subcontractor for prime contractor W.A. Rasic Construction Inc., completed a difficult compound curve microtunnel drive in the early hours of Wednesday, May 1, 2013. The SARI project relocates and replaces an existing wastewater pipeline that extends from the boundary of Orange and San Bernardino counties to the Orange County Sanitation District sewage treatment plant.

The SARI Mainline project initially was designed as a typical microtunnel project with several short, straight drives. Prior to construction, the construction team proposed combining multiple drives into a single long compound, or “S”, curve drive that would eliminate several shafts used for the launch and reception of the microtunnel boring machine.

John Fowler, Executive Vice President of James W. Fowler Co. said, “We recognize that this innovation would not have been possible without the partnership of the Orange County Public Works Department and its consultants, HDR, TetraTech, MWH Constructors and Hatch Mott MacDonald. Orange County showed great innovation by placing their trust in our team for this challenging project.  The project truly has the ability to revolutionize the North American tunneling industry by allowing greater design flexibility in microtunnel drive alignments.”

The curved drive utilized an innovative hydraulic gasketed joint designed to minimize point loading of the pipe joints during the jacking process without harming the integrity of the pipe structure. Swiss firm Jackcontrol AG manufactures the joint gasket and the associated real-time monitoring system, allowing continual monitoring of the jacking forces as the microtunneling process progresses.

Typically, a plywood ring is installed between two pipes to provide stabilization to the joints during pipe jacking. The Jackcontrol hydraulic joint system is filled with fluid, allowing the joint to be compressed on the inner side of the curve and expanded on the outer side of the curve to create a uniform loading of the pipe joint.  Sensor units built into the joints monitor the fluid pressure, evaluating and calculating the admissible jacking forces for each pipe to prevent damage.

The patented Jackcontrol joint system has never been used in North America, although it has been used extensively in Europe and Asia. German tunnel navigation system manufacturer VMT GmbH provided the alignment technology that ensured the drive met the design specifications.

Jeff Anderson, Project Manager, said, “James W. Fowler Co. appreciates the partnership of Jackcontrol and VMT in completing the first compound curved drive using the Jackcontrol hydraulic gasketed joint and the VMT navigations system. We made a great team!”

James W. Fowler Co., founded in 1970 in Dallas, Ore., by James and Candace Fowler, provides heavy civil and tunneling construction solutions to a variety of private and public clients across the United States.  Jackcontrol, founded in 2004, is an independent, internationally active engineering firm with headquarters in Glarus, Switzerland. The core business of Jackcontrol is in the fields of pipe jacking/microtunneling and the construction of hydroelectric power plants. VMT GmbH — the company for survey technology was founded 1994 to supply tailor-made solutions, services and surveying systems to the tunneling industry.

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