Bennett Trenchless provided trenchless assistance for the re-design of a critical US 50 crossing for Aerojet Corporation, after Aerojet’s initial proposal had been rejected by Caltrans. The original design was for a 30-inch auger bored crossing at shallow depth; the revised design installed the 30-inch casing via pipe ramming at increased depth to minimize settlement and heave risks to US 50. The geotechnical investigation conducted by Kleinfelder, Inc. indicated the presence of extensive gravel, cobbles, and small boulders which can pose significant challenges for many trenchless installation methods. A feasibility analysis was conducted to determine a recommended construction method that could handle the challenging ground conditions while minimizing ground movements. The heave calculations conducted for the project used a new approach developed specifically for the challenges presented by the project.
The revised design recommended the use of pipe ramming as the installation method. In addition, it was recommended that the alignment be deepened to reduce the risk of ground movement, which was crucial to securing the Caltrans encroachment permit. As a condition of the permit, Caltrans insisted that BTE serve as specialty inspectors and conduct settlement and heave monitoring to ensure protection of US 50 and existing utilities. The project was successfully completed without damage to Caltrans facilities in 2010.