Sounds like this “engineer” is well respected (i.e. to be 1500 miles away & “sought out this advice”).
Engineers have stated that the large MS concrete crest structure & sluice gate is anchored in bedrock. This seems to infer that the “vulnerability” is to protect the sub structure of the main spillway (slabs & sidewall system).
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I believe that is exactly correct.
The issue has apparently been the subject of heated debate on multiple occasions in the past.
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