By rosebell
The construction process of the last stretch of a 1,736-foot tunnel adjacent to the Anderson Dam in Santa Clara County, California, that will enhance Valley Water’s ability to release water from the reservoir during emergencies, thereby improving the dam’s safety measures, has been completed as Santa Clara Valley Water District (Valley Water) has announced.
The drilling process of the final 347ft, and reaching depths of 30ft beneath the water’s surface, was done by crews using a specialised micro-tunnel boring machine (TBM), whereas in the previous month, divers and crane operators removed the TBM, lifting sections of the machine using a large crane.
As the California public agency responsible for managing the water resources in Santa Clara County stated, although the tunneling work is complete, additional tasks remain before dam construction can commence.
In order to accommodating increased water flow from the new outlet tunnel, Valley Water is preparing the downstream creek channel and is installing a structural lining inside the tunnel to ensure added support.
As part of the larger $2.3bn Anderson Dam seismic retrofit project, the Anderson Dam tunnel project after completion of its new larger tunnel is going to increase Valley Water’s capacity to release water from the reservoir in emergencies, boosting the dam’s safety measures.
Also the diversion outlet structure between the tunnel entrance and Coyote Creek, is target of the significant progress.
While the structure has been built with 30-foot walls and connected to the tunnel by large-diameter steel pipes, it is designed to reduce the flow of water as it exits the reservoir before it enters the creek.
The estimated date for completing this project by Valley Water is mid-2025 and the scheduled date for commencing the next phase that will involve retrofitting the dam to withstand a major earthquake, is 2026.
Currently, the public agency is finalising the project’s design, securing permits, and undergoing environmental review.
With the aim of supplying close to one million people needs annually, the Anderson Dam seismic retrofit project will bring the reservoir’s capacity to around 90,000 acre-feet once completed.
The 2032 is planned date for completing Anderson Dam seismic retrofit project.
