<p><pre><code>    With a small dam the water can sometimes be drained,
    allowing repairs to be done safely. But imagine trying to 
    drain the Hoover Dam to repair cracks at the bottom--it 
    can&#x27;t be done
</code></pre>
I don&#x27;t understand why they think it&#x27;s a problem to drain the dam. It&#x27;s done regularly to check and repair them. (Every 30&#x2F;40 years, at least in France).<p>Recent video of this in France : <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=JflFg5un5zg" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=JflFg5un5zg</a><p>It is this dam, this is not a small one : <a href="https:&#x2F;&#x2F;fr.wikipedia.org&#x2F;wiki&#x2F;Barrage_de_Sarrans" rel="nofollow">https:&#x2F;&#x2F;fr.wikipedia.org&#x2F;wiki&#x2F;Barrage_de_Sarrans</a>