The Anderson Dam tunnel project hit a major milestone on Wednesday in the effort to protect the South Bay from the next major earthquake.
The last boring machine parts have now been pulled out of the Anderson Reservoir in Morgan Hill, signaling the end of the major tunneling part of the project.
It took nearly two years for them to dig more than 1700 feet next to the dam.
“Driving a drilling machine from inside of a tunnel, a lake. There were a lot of things we were anticipating could go wrong, and it all went pretty smoothly,” said Ryan Mccarter, Andersom Dam's project manager.
In May, NBC Bay Area got a tour of the tunnel during the excavation. Now, there’s a clear path from the reservoir down to the Coyote Creek.
“The next step is to line the tunnel and complete the piping basically to be able to put water through it,” McCarter said.
In the future, if the dam gets too full too fast, the new pipe will be used to release water from the reservoir via the tunnel and into the coyote creek below at a controlled speed.
It's a feature, that many believe could have help prevent flooding in 2017 when the reservoir spilled over.
“This project, when we’re done, will allow us to make [water] releases four times greater than what we can do with the existing pipe,” McCarter said.
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The latest retrofit was mandated by the federal government after studies found the dam could fail in a major earthquake and if it was full at the time could send a devastating wave of water across the Santa Clara Valley.
Having the tunnel in place also allows the water agency to keep the levels low during construction.
“So, all these physical components have to be done before we can start a reconstruction of the dam,” McCarter said.
Next up, crews will finish clearing coyote creek so it can handle more water flowing through it. In 2026, the construction on the dam itself will begin.
“We’re very excited to get this first phase of the project tunnel completed so we can now get the second phase which is completion of Anderson Dam,” said John Varela, Valley Water Board.
The dam is scheduled to be finished by 2032.
