State protects underground sources of drinking water

David Bunn
David Bunn

As leaders of the state agencies charged with regulating oil production, we believe that safeguarding drinking water and all potentially usable water is a fundamental government responsibility, and our agencies are working together to meet that responsibility.

We are also concerned about how misleading information being put forward on this issue is not helpful to the public (“Injection of wastewater into oil wells imperils drinking supply”; Viewpoints, Feb. 23).

Bringing California back into full compliance with the federal Safe Drinking Water Act is the state’s objective. Doing so requires that underground sources of drinking water – and aquifers of beneficial use – are protected from contamination.

Unfortunately, the op-ed needlessly capitalizes on a general misunderstanding that all aquifers are of beneficial use; aquifers in or near oilfields oftentimes naturally contain material no one should drink: minerals such as arsenic and boron, high concentrations of salts, and petroleum.

In California, almost all oil pumped to the surface comes with a much larger amount of groundwater. That “produced water” is injected back underground after being separated from the oil – without any harm to sources of drinking water. Sometimes that injection is to enhance oil recovery.

Federal and state laws and regulations govern “aquifer injection.” The federal Safe Drinking Water Act defines the quality of groundwater that does and does not need to be protected, including some groundwater not suitable for drinking.

In order for oil producers to inject water into certain geologic zones, the U.S. Environmental Protection Agency must grant an “aquifer exemption.” An exemption is based on scientific evidence that shows, for example, that the aquifer isn’t a current or future source of drinking water due to the natural state of the groundwater and that injected material will stay in the intended aquifer because of geologic barriers, such as layers of impermeable rock.

After carefully reviewing hydrologic and geologic data, the California Department of Conservation’s Division of Oil, Gas, and Geothermal Resources and the State Water Resources Control Board must concur that an exemption is appropriate. The process for making decisions about aquifer exemptions is fully transparent, including public meetings and comment periods.

The U.S. EPA has the final say about whether an exemption is granted. Each agency involved has a mandate to protect sources of drinking water. All of the aquifer exemptions the state is seeking are for aquifers that naturally contain petroleum, are brackish, and/or do not contain water that could be used for irrigation or household purposes.

As part of this comprehensive review, the state also has taken measures to protect aquifers that are potential sources of drinking water by requiring oil producers to shut down hundreds of injection wells.

The fact that we have an oil industry in California is evidence that some of our aquifers are naturally mixed with petroleum. Any fair and accurate assessment of how California regulates oil industry injection should begin with that understanding.

David Bunn is the director of the Department of Conservation and can be contacted at Thomas Howard is executive officer of the State Water Resources Control Board and can be contacted at