LIVERMORE — Amid greater scrutiny of oilfield contamination threats to California’s groundwater, state officials will hold a hearing Wednesday on a proposal to expand the aquifer area where a Livermore driller is permitted to dispose of oily wastewater.

Some environmentalists will speak out against the proposal by E&B Natural Resources for federal permission to expand the aquifer exemption area where it is permitted to put wastewater from oil extraction.

“We should not be putting this waste from the oil industry underground where it puts nearby water sources at risk,” said Patrick Sullivan, a spokesman for the Center for Biological Diversity, a national environmental group with offices in Oakland.

He said seismic activity along the nearby Greenville Fault exacerbates risks that waste with oil and production chemicals could seep into other Livermore Valley aquifers used now or perhaps in the future as drinking water.

The state hearing will be held at 5 p.m. at the Livermore City Council chambers, 3575 Pacific Avenue.

E&B Natural Resources, an oil company, is seeking the disposal area expansion to support continued operation of its 30-barrel a day drilling operation in a rural area east of Livermore.

Two state agencies are leaning toward backing the oil companies’ request.

The California Division of Oil, Gas and Geothermal Resources and the state Water Resources Control Board, have given preliminary support to the proposal.

Officials at those agencies say groundwater underlying the Livermore oil field naturally has petroleum and such a high mineral and salt content that it is not suitable for drinking water.

Don Drysdale, a spokesman for the state oil division, also said that officials now realize that the area permitted for oil disposal in 1983 is smaller than the actual aquifer where disposal has been taking place. As a result, expanding the area for allowing disposal matches the size of the area where E&B is putting wastewater — an area called the Greenville Sands section of the Ciebro Formation, Drysdale said.

“We propose the area where they are taking groundwater is larger ( than previously thought) in the past so the exemption should reflect that,” Drysdale said.

Oil drillers such as E&B typically pull up a mix of oil and water from underground geological formations, and then extract the oil and put the water back underground.

State officials say they do not believe earthquakes on the Greenville Fault will cause wastes to move underground for miles to contaminate aquifers for drinking water wells.

The final decision to expand the exemption area where E&B is allowed to dispose oily water is up to the federal Environmental Protection Agency.

In April last year, federal auditors criticized the EPA for not doing enough to protect underground drinking water reserves from oilfield contamination. The auditors said EPA oversight was weak in California, where the state was allowing oil companies to dispose of wastewater into some drinking water aquifers.