California regulators on Tuesday acknowledged lax oversight by the state had allowed oil and gas industry contamination of protected water aquifers and other threats to public safety, and they pledged to intensify protection of water sources and public health. “This is our chance to get it right,” John Laird, the state’s secretary of natural resources, told state senators in a scathing Senate hearing that examined what regulators conceded were decades of improperly permitted injection by the oil industry into federally protected water aquifers, as well as state approval of what lawmakers and environmentalists said appeared to be illegal use of potentially dangerous high-pressure steam injection in oil fields in California, the country’s No. 3 oil-producing state.