From what I've read in the local news, the chemicals were already in the soil, but dumping the waste into the (only) drainage system available without treating it first is apparently a no-no.

https://www.reviewjournal.com/news/environment/no-boring-co-...

https://www.reviewjournal.com/news/politics-and-government/c...

This reminded me of another local story (I live in both locations). The local swimming hole was fined for releasing seawater back to where it came from, cleaner than it was beforehand.

https://www.dailybreeze.com/2010/01/20/redondo-beach-asks-li...

https://documents.coastal.ca.gov/reports/2018/8/th13b/Th13b-...