Old old news, by way of public television. Rangers fired shotguns, I think, to scare off the birds from their nesting areas. The selenium was making for birds with birth defects.
Because California soil in the Central Valley was once seabed, it has seabed minerals in it, and ag watering washed them out of the top of the soil to the water that would build up deeper in the fields. The water buildup was mineral-rich to the point where it damaged crop roots if the water table rose high enough, so the farmers' remedy was to pump out the ground water and send it downriver.
Booty .... the boron & selenium problem is primarily a San Joaquin Valley problem, specifically Kesterson Reservoir historically speaking.