Nearly Full Anderson Reservoir Alarms South Bay Amid Concerns of Flooding

The Anderson Reservoir is said to be at 99 percent of its maximum capacity and on Thursday it stoked flooding fears in the South Bay.

It the Morgan Hill dam's water level rises much higher, it could have major implications for people who live along Coyote Creek

During a years-long historic drought in California, the reservoir's water level dipped so low that homeless encampments cropped up in the area and trees began growing in the middle of San Jose's Coyote Creek. However, after a storm-drenched winter, the dam has become something of a tourist destination. Many watch transfixed as millions of gallons are being released into the creek below.

With four storms heading for the Bay Area, though, water district officials are now cautioning people who live nearby that there could be some flooding.

Until the dam is seismically retrofitted, the water district is required to keep the reservoir level below 68 percent capacity. To that end, officials have been releasing about 400 cubic feet of water per second for the past week, but that's not been fast enough to keep up with recent relentless rain.

The Anderson Reservoir sits in an earthquake zone and the dam, which was built in 1950 when seismic standards were not as strict as they are today, could be damaged by a 7.25 magnitude or greated earthquake, according to Santa Clara Valley Water District spokesperson Marty Grimes.

Officials have been developing a plan to retrofit the dam since 2009, but the soonest the water district would commence construction would be in 2020.

"It's going to be a bigger project than we initially thought and that's part of the process," Grimes said. "As you go through the design process, you learn more about how the structure of the dam was built, how it's compacted, what kind of materials are in the dam. ... Nobody is more eager than we are to get that project completed."

The $400 million seismic retrofit project, which would partially be paid for by a parcel tax and increased water rates spread out over 30 years, would likely take at least four years to complete, according to Grimes.

Meanwhile, on Thursday, water in the reservoir inched closer to a critical spill way.

“The more pressing issue is the run off is going to affect Coyote Creek,” Grimes said.

Homeowners near the dam aren’t at high risk for flooding, but downstream in San Jose, there are a few low-lying vulnerable spots. One is the Golden Wheel Mobile Home Park in the Berryessa neighborhood.

To protect residents of the mobile home park, the water district raised a levee wall early this winter.

Unlike the potentially catastrophic situation with Lake Oroville's emergency spillway, the Anderson Reservoir's operational spillway is not at risk of failure, according to water district officials.

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