Oh..so its OK that the EPA breached a settling pond hey?
Back in the day...was there several dams supplying water to huge areas like now?
They leached those contaminations slow back then, not that it was acceptable. They had nearly no idea and most likely did not care either.
Of course it's not ok; I'm just providing some contrast to any presumption that this damage is irrevocable. Until this event modern folks thought of these streams as clean. Back in the day they weren't so how had they gotten that way. Mainly by passage of time. Back in the day there weren't near as many people living in this watershed, but those who did got their water from it. Their lack of knowledge and caring wouldn't have protected them from being affected by it, although their shorter life spans might have helped. If anything I'd think having the dams would help: the reservoir volume increases the dilution factor and the slower flow increases the sedimentation rate in what had been fast streams. Back in the day folks got their water, untreated, straight from the watershed. Nowadays water for homes, restaurants, motels, etc. will be pre-treated to 'safety' in spite of this. The spill may provide some supply limitations, but back in the day the supply was likely less and they couldn't truck in extra at need. Contamination of fish and game is a concern, but alternative supplies can be shipped in. Folks won't starve from their lack. Recreational exposure and exposure via irrigation remain a concern, but those weren't widely available back in the day. They, along with the fish and game, will recover in time.
Meanwhile my advice is to take the 'fine' specifically from the pile of funds available for EPA employee bonuses and specifically ban adding to that pile. Consider taking the entire cleanup and monitoring costs of this misadventure from there.