State of California identifies Lopez Dam as “high-hazard”
June 14, 2017
San Luis Obispo County’s Lopez Dam near Arroyo Grande is a “high-hazard” reservoir, according to an recent assessment conducted by the state of California.
Earlier this year, the Oroville Dam’s primary spillway suffered damage and began to erode. Then the emergency spillway failed which prompted evacuations of more than 180,000 Northern California residents.
Failures at the Oroville Dam prompted the California Division of Safety of Dams to reevaluate large spillways at high-hazard dams. The agency determined Lopez Dam may have potential geologic, structural or performance issues with its spillway, according to a letter from the Division of Safety of Dams to the San Luis Obispo County Flood Control District.
The state agency has reportedly identified more than 50 “high-hazard” dams in California. Whale Rock Reservoir near Cayucos is reportedly on the list, as well.
State officials are requesting that SLO County perform a comprehensive assessment of Lopez Dam’s spillway as soon as possible. The assessment should include an evaluation of the concrete lining, the existing drainage system and the potential for slab undermining and hydraulic jacking.
Dam safety official say they may also require a spillway site investigation. The investigation should focus on identifying potential geologic hazards associated with the spillway, including foundation materials beneath and adjacent to the spillway, as well as their susceptibility to erosion and instability.
The state is ordering the county to submit a work plan by September 1. Dam safety officials say any damage to Lopez Dam’s spillway must be repaired before the next flood season.
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