Shocking how incomplete this article is. One of the prominent sites was caused by Fairchild, and it's specifically described in Gordon Moore's autobiography. he said they just dumped strong acids down the drain, unaware that it ate a hole in the drainpipe, and so all the other solvents they dumped down the same drain ended up hitting the water table and pluming (https://www.amazon.com/Moores-Law-Silicon-Valleys-Revolution...).

he claims he didn't know that would happen, but every trained chemist learns to neutralize their acids before dumping them down the drain.

AFAICT, Moore and his buddies never had to pay anything for this- the companies settled with the government.