El Dorado Chemical Company (EDCC) makes chemicals. Flat Creek, Haynes Creek, and two unnamed tributaries (UTA and UTB) don't make anything, but they're waterways in Arkansas with little fishies in them. The EPA protects the fishies. As part of its operations, EDCC discharges minerals into the water.
This is OK -- a little bit. Arkansas enforces water standards through a program called the National Pollutant Discharge Elimination System (NPDES). A company can't discharge things into the water without a permit from NPDES, which includes limitations on amount and type of discharge; the EPA must approve these permits.