[gwbas1c]

> wouldn't you expect to hear about water tables that have problematically-high natural levels of this or that heavy metal?

Where I live, I get periodic water quality reports in the mail, with the test results for all kinds of different contaminants.

The reports always list the typical source of contaminants; and naturally-occurring metals in the ground is very common.

Interesting artifact: A well near my childhood home has unusually high levels of chromium for the town. It's believed to be from when someone was running a car repair shop near the watershed; and they left some brake drums or similar car parts outside.

[FreshStart]

It's usually not that. It's usually the car repair shop pouring left-over chrome containing colors and derusting solutions into the ground.