The Coast News Group
San Onofre tsunami: A map depicting underwater topography off the coast of Southern California near the decommissioning San Onofre Nuclear Generating Site. Graphic courtesy of Scripps Institution of Oceanography
A map depicting underwater topography off the coast of Southern California near the decommissioning San Onofre Nuclear Generating Site. Graphic courtesy of Scripps Institution of Oceanography
Cities Environment News Oceanside Region

Despite renewed concerns, San Onofre nuclear site safe from tsunamis

REGION — Despite scientific research indicating a lower-than-expected risk of tsunami danger to the decommissioning San Onofre Nuclear Generating Station, a recent tsunami event has prompted renewed concerns from a local activist group about the possible impact of a bigger, similar-type natural disaster on the nuclear plant and its spent fuel.

Following a Jan. 15 tsunami triggered by a volcanic eruption off the coast of Tonga, local activist group Public Watchdogs raised concerns over what a more catastrophic tsunami could do to the decommissioning San Onofre Nuclear Generating Station, or SONGS, and its fuel storage.

“Our worst-case fear is that a tsunami would breach the seawall and clog the passive-air cooling system at the beachfront San Onofre nuclear waste with mud and debris,” said Charles Langley, executive director of Public Watchdogs. “A second concern is that the analyses do not consider the possibility of partial flooding of the silos that hold the canisters. Because of the design of the cooling system, a partial flood would be far riskier than a complete flood.”

According to the SONGS Community website, larger, more destructive tsunamis like the one that the Fukushima Daiichi Nuclear Power Station in Japan in 2011 typically generate from earthquakes in subduction zones. Tonga, more than 5,000 miles away, is also located near a subduction zone.

The decommissioned nuclear site, located on the shoreline of Camp Pendleton near San Onofre State Beach between Oceanside and San Clemente, is next to a strike-slip fault system, which is only known to create between 10 to 15% of earthquake-induced tsunamis as opposed to subduction zones.

John Dobken, a spokesperson for Southern California Edison, also noted that the seawall protecting the spent fuel storage is 28-feet high, and even if water breached the wall, the storage system is designed to be inundated with 50-feet of water and still perform its safety functions. Plus, Dobken said other geological conditions help further protect San Onofre from tsunamis.

“First, there is no historical evidence of underwater landslides that would generate a large near-field tsunami,” Dobken wrote in a recent post. “The second is the baffling effect created by the California Borderlands, the offshore seafloor topography of canyons and peaks which would muffle any far-field tsunamis.”

Much of this information comes from research conducted by Dr. Neal Driscoll of the Scripps Institution of Oceanography in 2017. According to Driscoll’s data, the San Onofre-area coastline is not as vulnerable to tsunamis as other parts of the West Coast. Based on maps of underwater peaks and canyons, Driscoll said the geology offshore would likely slow a tsunami down.

“Our research shows that the risk or geo-hazard of the faults offshore when we first started this study are less than what we had predicted before,” Driscoll previously told KPBS.

According to the Nuclear Regulatory Commission, or NRC, the maximum flood height at San Onofre is 27 feet, including run-up from a tsunami and wind-driven waves.

The NRC responded to several of Public Watchdogs’ concerns, including about flooding and tsunamis, that were listed in a petition the group formed in 2020. The petition sought to halt the decommissioning process on the grounds that the ISFSIs were operating under an “unanalyzed condition.”

“The NRC provided a lengthy response to the flooding concerns of Public Watchdogs last year,” Dobken told The Coast News. “Public Watchdogs has chosen to simply ignore this information without providing any new analysis or data.”

Leave a Comment