Rivers are NOT comparable to babies. Each baby has an immortal soul as rivers do not.
As to all these "environmental" fads, I have never been moved. We all have some limitation as to the number of causes we can be involved with and as to the intensity of each involvement. I will leave the environmental stuff to you and Bergoglio and absolutely refuse to get carried away like illegitimate antipope Frankie with the insanity that there are "environmental sins." How ridiculous!
When secular politicians bring out their "environmental" oompah bands to gull the suckers, they are using an "environmental" agenda to bludgeon business and a free economy for their own Marxist agendas. It is no accident that the late unlamented envirowhacko US Senator Gaylord Nelson (Marxist-Leninist-Wisconsin) chose Lenin's birthday to be the Annual "Earth Day."
Meanwhile, as a Catholic, I will say that Commissar Frankie should depart as soon as humanly possible and pray that God send us as soon as possible a young, healthy, physically and intellectually and spiritual man with actually CATHOLIC views to replace the colossal blunder of the last conclave and then let each and every Frankie sympathizer be purged in favor of Catholics.
So, in short, you don't see any moral problem with dumping a few tons of mining sludge into the local river.