In California, the cities' water supply depends on the reservoirs along the Colorado River and in the Sierra Nevada. Water flows through hundreds of kilometers of aqueducts, canals, pipelines and tunnels. To safeguard the water supply in the large area around San Francisco Bay, a new pipeline from the mountains to the reservoirs was to be built. For the instalation of the pipeline in the densly populated area of Walnut Creek, trenchless technology was favoured. For reasons of cost, the tunnel had to be lined with 1.5-meter-long wooden slats and steel rings (Rib & Lagging).
Due to the geological requirements, the machine chosen was an EBP2400AB, with a mixed cutterhead fitted with a laser steering system. Because of the curves, (minimum radius: 366 meters), the motorized laser theodolite had to be continually adjusted to ensure that the laser beam was able to hit its target. This led to a considerable reduction in tunnelling performance. Herrenknecht's solution was to add a gyrocompass, combined with an inclinometer, to the existing equipment. The gyrocompass was mounted in the machine. In combination with the laser input, a reliable navigation was thus provided, allowing best tunnelling performances of up to 38 meters per day.