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Emergency repairs ordered at Nacimiento and San Antonio dams before rainy season

Water from Lake Nacimiento flows down the dam’s spillway earlier this year.
Water from Lake Nacimiento flows down the dam’s spillway earlier this year. jjohnston@thetribunenews.com

The state has ordered urgent repairs of the Nacimiento and San Antonio dam spillways before the rainy season, a result of assessments following the failure of the Oroville Dam spillway earlier this year.

The Board of Supervisors of the Monterey County Water Resources Agency this week allocated up to $500,000 for the repairs.

Both dams are classified as extremely high hazard, and the same conditions that caused Oroville’s near catastrophe in northern California were found at Nacimiento and San Antonio, according to a Monterey County staff report.

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Minimum work required by the state includes filling joints and cracks, replacing damaged concrete, removing raised edges on downstream cement slabs and walls and ensuring spillway drains are functional, the report says.

The state agency that manages the safety of 1,250 dams in California sent letters to the operators of 93 dams this summer directing them to create a work plan for a comprehensive assessment of the dam spillways.

Operators were told their dams may have design flaws and must undergo assessments “as soon as possible.”

Operators of Lopez and Whale Rock dams in San Luis Obispo County received the letters from the Division of Safety of Dams and have responded, but they were not ordered to complete any repairs before the upcoming rainy season, operators said.

Nacimiento Dam is located in San Luis Obispo County and the reservoir supplies water to the county. It is operated by Monterey County.

Mark Hutchinson, San Luis Obispo County's deputy director of Public Works, takes The Tribune on a tour of the cement Lopez Dam spillway, designed to release water and protect downstream communities from flood. He also talks about the steps taken t

For the first time in nearly six years, Santa Margarita Lake is full and spilling over into the Salinas River. Mark Hutchinson, deputy director of SLO County Public Works, talks on Feb. 8, 2017, about the role of the lake, also known as the Salina

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