The Kern River Oil Field is the 5th largest in the US and the densest in California. Wastewater was once allowed to drain directly into the streams dissecting the region, and thence into the Kern River. This practice ended in the 1970s when more stringent environmental regulations were enacted. The oil field covers an area of 10K acres in the hills near Bakersfield, hills which are now almost completely barren except for oil rigs, drilling pads and equipment. The principal operator is Chevron.