Victoria Canal Conveyance Pipeline: Micro-Tunneling for Water Diversion
The Victoria Canal Conveyance Pipeline was a critical part of the Contra Costa Water District’s Alternative Intake Project (AIP) near its facilities in the San Joaquin Delta region of California, east of the San Francisco Bay. The AIP diverted raw water from a new intake pumping plant through a 72-inch pipeline, requiring an approximate 900-foot crossing under the Old River. This crossing involved installing a 96-inch steel casing using micro-tunnel pipe-jacking techniques, necessitating a 90-foot deep jacking shaft and a 70-foot deep receiving shaft.
Malcolm Drilling designed and built the access shafts using the Cutter Soil Mix (CSM) method. CSM panels were installed at the receiving shaft first, followed by the jacking shaft. Using a Bauer BG 40 with a CSM attachment and BCM 10 cutting wheels, Malcolm constructed overlapping CSM panels, each measuring 3.3 feet by 9.2 feet, in a circular pattern. These panels provided shoring for the excavation and acted as a cut-off wall to prevent water ingress, allowing excavation in dry conditions 60 feet below the water table.
The receiving shaft panels were mixed to a depth of 58 feet, with excavation reaching 50 feet, while the jacking shaft panels were mixed to a depth of 103 feet, with excavation reaching 95 feet. Slurry from the CSM process was pumped to a temporary storage basin and later moved to the final on-site disposal area. Wet grab samples were collected from each panel for compressive strength testing.
Excavation and shotcrete application proceeded on a three-day cycle for each 5-foot lift. Upon reaching the final shaft elevations, a reinforced concrete seal slab was installed, followed by reinforced shotcrete structures to accommodate tunnel penetrations and the Micro-Tunnel Boring Machine (MTBM) jacking forces.
The completion of the Victoria Canal Conveyance Pipeline allowed the successful installation of the 72-inch pipeline, ensuring effective water diversion from the intake pumping plant under the Old River.
