For the Victoria Island Conveyance Canal Pipeline near Discovery Bay, California, Malcolm Drilling constructed access shafts for micro-tunneling a 96-inch diameter steel casing under the Old River, to allow for the installation of a 72-inch pipeline designed to divert raw water from the new intake pumping plant.
Using a Bauer BG 40 equipped with a cutter soil mixing (CSM) attachment and BCM 10 cutting wheels, Malcolm soil mixed overlapping CSM panels (3.3 feet x 9.2 feet) in a circular pattern to construct the access shafts. The CSM panels provided shoring for the excavation of each shaft and also worked as a cut-off wall to prevent water from entering the shaft. Excavation continued in the dry despite being 60 feet below the water table. Panels for the receiving shaft were mixed to a depth of 58 feet and the shaft was excavated to a depth of 50 feet. Panels for the jacking shaft were mixed to a depth of 103 feet and the shaft was excavated to a depth of 95 feet.
