A project that is now more than $400 million over budget reached a milestone Tuesday.
The brand new spillway of the Calaveras Dam is complete, officials say. It is as wide as an eight-lane freeway and is built to handle a magnitude-7.25 quake.
It is important for the structure to be able to withstand a major quake because the Calaveras Fault is just 1,500 feet away from the existing dam, according to officials. Construction on a new dam kicked off in 2011.
This week, crews finished building the spillway – an important safety feature to control the release of water from the Calaveras reservoir, which has, in the past, been kept at a low level because the old dam wasn’t quake safe.
Bringing the reservoir to “full capacity” provides a “critical” water source for the nearly two million customers in the Bay Area, said Steven Ritchie of the San Francisco Public Utilities Commission.
It has not been smooth sailing, however, to erect the new dam. The final project has been delayed by three years and will cost a whopping $810 million.
When asked why the cost of the project nearly double what was anticipated, Dane Wade, director of the SFPUC’s Water System Improvement Program, said, “This has been a very complex project from a geologic standpoint.”
Specifically, crews discovered several ancient landslides that were too unstable to build on. So the dam had to be redesigned and much more dirt had to be hauled out, which cost more money.
Crews have had to relocate enough rock soil to cover all of Treasure Island with seven feet of dirt, officials said.
Another challenge included making sure the naturally-occurring asbestos in the rocks don’t pose a threat to workers and the public.
The SFPUC says the additional costs of the project will be covered with money from other funds, and water customers should not expect to pay beyond the gradual increases that were already planned.
Construction of the entire dam should be complete by spring 2019.