Erin Brockovich

In the flyer PG&E distributed to neighbors of the compressor station, the company talks about adding chromium to the cooling process:

Small amounts of chromium were commonly added by industries to cooling towers to prevent corrosion and scaling.

"Small amounts" wouldn't cause neighbors who owned ranches and dairy farms to worry much. But here is how the plaintiffs' trial brief describes actual amounts used by PG&E:

By 1966 an estimated 65 tons of chromate-based corrosion inhibitors were discharged into the unlined ponds

while the Sun's High Desert Bureau relates what those levels actually meant to the people breathing the air and ingesting the water:

A biochemist said concentrations of highly toxic chromium VI in the groundwater basin reached peak levels of 1,000 to 5,000 times the safe limit for drinking water and more than 50,000 times the safe level for inhalation.

PG&E didn't line the ponds until 1972. The company sent 750,000 additional gallons of chrome 6 wastewater every month to the ponds for another six years.

Once the toxic material was in the unlined ponds, there was nothing to stop it from migrating to the wells that supplied nearby homes, farms and ranches.