Guided Auger Boring
As a subconsultant to Carollo, Bennett Trenchless Engineers provided trenchless design services to the City of Sacramento for 250 feet of pilot tube guided auger boring beneath Union Pacific Railroad (UPRR) tracks in Sacramento, CA. The 20-inch steel casing was installed for 12-inch cement-mortar lined and coated steel water pipeline to maintain adequate water supply and system pressure. The only feasible launching and receiving locations for trenchless installation of the new pipeline were an industrial laundry parking lot and a community baseball field. Challenges included strict construction schedule requirements to avoid impacts to the baseball field during baseball season, multiple existing utilities and surface features resulting in constrained alignment alternatives, minimizing impacts on the community, and necessary coordination with UPRR to avoid delays. The pipe alignment was selected to be above groundwater in medium stiff and medium dense mixtures of sand, silt, and clay to mitigate settlement risk to the UPRR embankment and tracks.
During preliminary design BTE reviewed the geotechnical data, performed design calculations, analyzed feasible trenchless alternatives, and provided recommendations for the most appropriate trenchless construction method. BTE also provided final design services including drafting technical specifications, providing drawing edits, developing a settlement monitoring plan, providing technical assistance to acquire the UPRR encroachment permit, and review of construction submittals. The project was successfully completed on schedule and without any observed settlement of the railroad tracks.