Watch the water
https://pittsburgh.cbslocal.com/2021/11/05/valley-forge-national-historical-park-milk-in-creek/
An accident like this happened in Wales in April 2021. Article mentions someone on twitter said it was biblical.
https://www.newsweek.com/massive-milk-spill-turns-river-white-alarming-images-1583888
Article from 2012
https://www.gawker.com/5879234/spilt-milk-actually-kills-fish-and-screws-up-the-water