As a specialty trenchless consultant to Black & Veatch, Bennett Trenchless Engineers provided design and construction management services for the 54-inch diameter water main crossing of the American River near Howe Avenue and the Fairbairn Intake. The project consisted of a single 1,410-foot, 54-inch diameter microtunneled drive, from a 28-diameter, 79-foot deep concrete caisson jacking shaft to a 20-foot ID , 74-foot deep auger drilled reception shaft. The geotechnical conditions were predominantly hard sandy silt overlain by a 20-foot thick layer of gravel with cobbles and boulders and high groundwater. The deep alignment was chosen to avoid complications with tunneling in the gravel with cobbles and boulders, and to position the pipe below anticipated future scour elevations associated with a 100-year flood event.
Bennett Trenchless prepared a technical memorandum recommending microtunneling as the preferred construction alternative, recommending alignment and depth, and developed a planning level cost estimate. Design also included selection of the crossing alignment to minimize impacts to the existing water treatment plant on the south end of the crossing and to California State University – Sacramento on the north end of the crossing. Shaft locations were selected to avoid adverse impacts to the stability and performance of the flood control levees on both sides of the American River. Bennett Trenchless conducted settlement and jacking force calculations, and prepared technical specifications and drawing details for the microtunneled crossing design. BTE also provided submittal review and specialty, full-time, on-site construction management services.