Swollen Anderson Reservoir Spills Over For First Time in 11 Years

The Anderson Reservoir, which has hovered around 99 percent of its maximum capacity for the past few days, began to spill over early Saturday morning for the first time in nearly 11 years.

As the Morgan Hill dam's water level rages, people who live along Coyote Creek could be under risk of flooding. So officials opened the spillway on Saturday to relieve pressure on the reservoir and make room for more water from the approaching storms. 

"I think it’s amazing. It’s never been so full," said Nick Smith of Morgan Hill.

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 have flocked to Anderson Reservoir, watching transfixed as millions of gallons were released into the creek below.

"It's pretty awesome," said Kelly Truman of Morgan Hill. "We rarely get this much water and we got our show."

However, Marty Grimes, a spokesman for the Santa Clara Valley Water District, warned of potential flooding as a string of storms make a beeline for the Bay Area in the coming days. 

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, he said. 

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 water district spokesperson Marty Grimes.

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 relentless rain.

At the current pace that the Anderson Reservoir is taking on water, Grimes estimated that it could take between four and nine weeks to reduce the water level so the dam is compliant with seismic regulations.

"That’s the physical reality," Grimes said. "We opened this release valve in January when the reservoir was only half full, in anticipation of that."

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.

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.

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