California's oversight of wells where oil companies dispose of wastewater brought to the surface during oil production is hindered by inadequate staffing and poorly organized paper records, a state review of the program said Oct. 8.

In a report to the legislature, California's Department of Conservation (DOC) found that wastewater injection wells also suffer from inconsistent permitting, monitoring and enforcement of their construction and operation, among other problems.

"We analyze past and present regulation of underground injection and find that the permitting unit - which was created over 50 years ago - has struggled and sometimes failed to embrace a transparent enforcement process driven by scientific research and best practices," said DOC director David Bunn.

Interest in wastewater injection wells and whether they pose a risk to drinking water supplies has risen as the state battles its worst drought in recent history.

In March the DOC and the U.S. Environmental Protection Agency (EPA) began reviewing the thousands of injection wells in the state to determine if any violate the federal Safe Drinking Water Act.

The DOC has already issued "shut-in" orders for 23 wells for violating the act and is testing to verify there has been no contamination of groundwater near those sites.

The DOC has said they have not yet found any indication of injection wells contaminating potential drinking water supplies.