Open Shield Pipe Jacking
As the trenchless subconsultant to Brown and Caldwell, Bennett Trenchless provided full design assistance, permit assistance, and trenchless submittal and RFI review for a trenchless crossing to replace an existing raw water pipeline. The existing pipeline was predominantly riveted steel pipe and open-channel conveyance that was installed in the early 1900s. During preliminary design, Bennett Trenchless evaluated several potential crossing locations, including an alternative for a trenchless crossing of the nearby UPRR tracks.
The final selected crossing location presented several challenges. It did not cross the UPRR tracks, but in this location I-80 was built on approximately 50 feet of embankment fill over an old road or railroad. The embankment fill had a high potential for unknown materials to be present, which posed significant potential risk for most trenchless methods. Two alternative trenchless designs were presented to PCWA: an open-shield pipejacking crossing in the fill and a deep microtunnel crossing below the fill in the native rock. The open-shield pipejacking alternative was selected, in part due to the challenges associated with access to the east side of the crossing and therefore in constructing a deep shaft. The trenchless component of the project was successfully completed in 2017.