With Anderson Reservoir on the verge of reaching the spillway for the first time in more than a decade, and with a catastrophe narrowly averted below Oroville Dam fresh in the public’s mind after last week, Morgan Hill City Manager Steve Rymer opened the latest council meeting with some words about local safety and evacuation plans in case disaster strikes.
Anderson Dam was determined by state and regional officials in 2009 to be seismically unsound, requiring a retrofit that won’t be under construction until 2020. Until then, because the dam could fail in the event of a major earthquake, state regulators have required the reservoir to remain at or below 68 percent of its capacity.
However, because the Santa Clara Valley Water District can’t release water from the reservoir faster than this winter’s storm waters have poured into the lake, it is now more than 99 percent full, according to the SCVWD website. If the reservoir surpasses 100 percent capacity, water will begin to flow over the emergency spillway, which is similar to that of many other reservoirs owned by SCVWD.
“That is what it is supposed to do,” Rymer said Feb. 15 of the Anderson spillway. The last time Anderson Reservoir was high enough to reach the spillway was in 2006. The water flows from the spillway into Coyote Creek.
Other nearby reservoirs—including Chesbro and Uvas—have seen the water rise to the spillway in recent weeks to prolonged rains.
While water flowing off the Anderson spillway could threaten some local flooding on Coyote Creek, Rymer and other officials do not anticipate any widespread emergencies.
“The water district does not believe the dam is at any risk, or the spillway,” Rymer said. State and federal authorities recently inspected the dam and spillway for safety under normal (non-earthquake) conditions, and both facilities passed the inspections. These inspections took place June 12, 2016.
Rymer added when the water reaches the spillway, it will be “nothing like Oroville,” where last week authorities evacuated about 200,000 residents below Lake Oroville. That emergency was caused by long-term damage to the dam’s spillway, but no such conditions exist in Morgan Hill.
Rymer also briefly assured residents that Morgan Hill, like other cities, has an evacuation plan in place in case a major natural disaster requires people to suddenly flee to safety. This plan largely relies on using U.S. 101 to move people out of town.
The city’s disaster plan also relies on multiple agencies—including Morgan Hill Fire and Police, other local fire agencies, California Highway Patrol, water district, county agencies and more—to assist and coordinate resources, Rymer said.
He also urged residents to sign up for AlertSCC, a phone alert system that can automatically notify thousands of people at a time when a disaster or emergency strikes. Sign up by visiting sccgov.org/sites/alertscc/Pages/home.aspx.
In a Feb. 16 press release, city staff also advised residents to make sure their household and family emergency plans are in place. Plan out the best route to higher ground, the safest place when flooding threatens, before any disaster might strike.
Residents are also asked to review the water district’s online Anderson Dam inundation maps and be aware of where and how quickly waters from the dam might reach their home, schools or places of business. The inundation maps are available on the SCVWD website.
