actually I have done some reading, which is why I said that...

actually I have done some reading, which is why I said that tailings dam are designed to trap toxic byproducts, and/or salts (i.e. clays and silica). I did not define anything, and heavy metals are not the only potential toxicities. And of course it is ore specific, as to what the contents of the byproducts are. But your statement that most mining does not release heavy metals is based on what evidence? Gold and copper mining is usually associated with heavy metal byproducts. The Samarco dam fail was enormous in the size of the water,sand and clay that flowed down that catchment (apparently a 40m3 wall). Of the approximately 3,500 industrial tailings dams worldwide, most are designed to trap toxic byproducts, and/or salts, as I said in my previous post.
Perhaps you need to read posts more carefully, before you jump on people.