Plans have been in the works for the last three years to build what would become one of the Bay Area’s biggest dams. But now, after a huge price increase, the much-anticipated project could be taking some big steps backward.
The cost to build the 319-foot dam on Pacheco Cheek north of Highway 152 not far from Casa De Fruta was supposed to be $1.3 billion dollars. But the Santa Clara Valley Water District has released a construction cost estimate update this week that takes the price of the project up to $2.5 billion dollars.
If it ever gets built, officials say it will hold 140-thousand acre-feet of water which would make it by far the biggest in the County. The biggest now is Anderson Reservoir which holds a maximum of 90,000 acre-feet.
For the last three years, county water officials were banking on Pacheco Reservoir to become a key component to the South Bay water supply and a way to help stay ahead of potential drought emergencies in the future.
According to the report, the length of the project’s completion has also ballooned by three years pushing the new finish date to the year 2027.
As the Mercury News reports, there is a newly-discovered, unstable rock layer that will force construction crews to dig down 30 more feet than originally planned to hit bedrock which will add hundreds of thousands of extra manhours and hundreds of millions of extra dollars to the project.
"There are historic slides in the area, loose material that is subject to movement. You don’t want to put your foundation on that obviously because if there is any sort of seismic event, or even heavy rains or mudslides, it could undermine the foundation,” Valley Water District Employee Chris Hakes told the Mercury News.
The new report also includes a PowerPoint presentation that lays out four alternative plans for dams along Pacheco Creek that are less expensive than the $2.5 billion dollar plan.
Three of the plans call for the dam to be built upstream from the current site because officials believe upstream areas have more suitable topography for dam construction.
One of the alternatives scales down the size of what would become Pacheco Reservoir, taking it from 140,000 acre-feet to 96,000 acre-feet to save money.
According to the Mercury News, the Valley Water District is scheduled to discuss the alternatives during a board member meeting on January 12th.
Currently, Pacheco Reservoir, if it can be called a reservoir, holds only 5,500 acre-feet of water with a dam that was built in 1939.
The Water District claims that expanding the body of water to 140,000 acre-feet would supply up to 1.4 million residents with water for one year in an emergency.