San Onofre shutdown will mean tight electricity supplies

[FBaggins]

69. Except that it wasn't "technically wrong"

Over topping a sea wall that was never intended to be overtopped at ALL, can have disastrous consequences.

Nope. That simply isn't true. You can't say that any amount of water over a seawall is dangerous. It's as oversimplified as saying "it's designed to withstand a 6.0 earthquake without damage, so a 6.1 will cause it to blow up". The backup generators are at about that level, but (unlike Fukushima) they're in waterproof bunkers. The backup batteries (and electrical switching) are 20-30 above that and have more than enough power to last until additional generators could be connected. There isn't a plausible scenario where a foot or two of water over the sea wall causes the plant to fail.

Upthread you seemed pretty sure it couldn't happen at all anywhere on the west coast, but the west coast HAS experienced tsunami higher than the top of that sea wall under some conditions.

Except that we just went through that and it wasn't. You artificially lowered the wall to 14 feet based on a fictional claim. The wall isn't 14 feet above high tide. You're also oversimplified the coastal geography. What I said was that the largest tsunami (not the tallest wave) recorded along the West Coast wouldn't endanger that wall. You'll note that there were significant differences in wave height along the coast of Japan during the tsunami... this is because the coast isn't uniform. A tsunami that forms a 14-foot wave in Seaview, WA (where the columbia river's delta impacts the hydrography) doesn't form a 15-ft wave off of San Onofre.

Here's the image that caused that misunderstanding. the creator is trying to demonstrate that 30 feet above low tide is really 14 feet above high tide... but the fact that you can see a splash at high tide is not close to the same thing as saying that high tide is at the base of that wall (and therefore 14 foot waves on top of that would overtop it).



But this isn't hard to confirm for yourself. Tide charts are online. Compare the highest tide level that you can find... you won't come close to the 16 feet required to validate their claim.

There are tsunami risk areas all up and down the west coast. I live in one. I can see an evacuation route sign from my office window, and on a clear day, three evac sirens.

See my previous reply to Creekdog. It's really not at all the same thing. California has had dozens of "tsunami" in the last century... but none of them deserve the same name as what we're talking about. A California tsunami is a warning of coastal flooding and to get off of the beach. Take a look at the map... in most areas it's just the beach. If you live in a low-lying area right along the coast it could mean minor flooding - nothing that endangers reinforced concrete seawalls.. In Japan it's a very different thing.

Apologies for the appeal to authority

Actual authoritative sources are not really the same thing as the "appeal to authority" fallacy. If they are subject matter experts (and they are) and there's no significant controversy among other experts (and there isn't)... it isn't "appeal to authority". Nevertheless... it's a misuse of the map - which doesn't take the seawall into account. This is easy enough to prove. The model used for the map generated a maximum tsunami of 20 feet above mean sea level (MSL). As has already been shown... the sea wall is well above that. This was confirmed by the California Coastal commission when the issue came up right after Fukushima.