Mark Nechodom, the director of the California Department of Conservation, which oversees the embattled agency that regulates the state's oil and gas industry, resigned Thursday.
Gov. Jerry Brown appointed Nechodom to the post three years ago. He took over an agency that has generated significant controversy.
California's oil regulator, the Division of Oil, Gas and Geothermal Resources, has been facing scrutiny from the U.S. Environmental Protection Agency after allowing oil producers to drill thousands of oilfield wastewater disposal wells into federally protected aquifers.
Nechodom was named this week in a federal lawsuit filed on behalf of a group of Kern County farmers who allege that Brown, the oil and gas division and others conspired with oil companies to allow the illegal injections and to create a more lax regulatory environment for energy firms.