Nope. Bonne Terre Mine in Missouri was an old lead mine. When I was there, we asked the same question. They said lead in its natural form is not toxic. After it is smelted is when it becomes toxic.
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That is some serious silt in there ! No flow & a silt out would make things interesting for sure. Reminds me of the flooded silver shafts up in Colorado at high altitude. Same deal.....cold water...masses of silt & no flow ! Be safe !
Cool video & nice technique too.