Anyone notice the arrival of a large, red machine at the San Antonio Backup Pipeline work site this week along Calaveras road (south of I-680)?
It is actually an excavator with a 100-foot long digging arm. Why, you might ask, would we need a 100-foot long digging arm to build a pipeline?
Good question! It will be used by one of the subcontractors on this project, Magnus Pacific/Inquip, a Joint Venture, to construct the cement slurry wall around an unused quarry pit in the Valley. When the project is complete, the pit will temporarily store occasional discharges from the Hetch Hetchy Regional Water System. To that end, we need to construct a deep cutoff wall to prevent groundwater from seeping into the pit in the future.
The large excavator will dig a deep trench while the contractor fills the trench with cement slurry. The slurry will keep the trench from collapsing, and it will harden over time to create the barrier that will keep groundwater out. The trench is deep, the ground is wet, and the work is difficult - perfect for the new machine out there.
Once complete in 2015, the San Antonio Backup Pipeline will add operational flexibility to the water system that currently serves 2.6 million customers.
See you around the Sunol Valley!