&gt; The write-up is in response to a question asking how long dams like the Hoover Dam, which is a large concrete dam, are designed to last. It wasn&#x27;t suggesting that all dams are concrete.<p>But the author mixes concrete dams with tailings dams, of which none (according to USACE) are concrete.  That&#x27;s what I meant by vague: starts with a large large number talking about US dams with, talks about concrete, mentions danger of tailings and then talks about foreign dams.  The data is chosen for a narrative and ends up implying a lot without clear references.