Who Is Accountable for Oil Waste in California Drinking Water?

Information released by the California agency then known as the Division of Oil, Gas, and Geothermal Resources raised a serious question: had poor records and weak oversight allowed oil and gas operators to inject wastewater into aquifers protected as potential drinking-water sources?

The extent of contamination was not established in the material discussed at the time. The disclosures nevertheless exposed failures by state and federal regulators to provide clear records, enforce aquifer boundaries, and demonstrate that scarce groundwater resources were being protected.

Why produced water matters

Oil and gas extraction generates wastewater commonly called “produced water.” Underground injection has long been a common way to manage that waste. Produced water may be far saltier than seawater and can contain heavy metals, hydrocarbons, and naturally occurring radioactive material. Once groundwater is contaminated, cleanup may be technically difficult or impractical.

Most wastewater injection is intended for geologic formations whose fluids are unsuitable for drinking, irrigation, or similar uses. Different rules apply when a formation contains water that meets the federal definition of an Underground Source of Drinking Water. Before injection can be authorized there, regulators must determine that the water is not suitable or is unlikely to be used and approve an aquifer exemption.

The exemption and recordkeeping problem

California had granted more than 1,100 aquifer exemptions, many dating to the early years of the Underground Injection Control program. The historical review described confusion about which aquifers were exempt, where exemption boundaries lay, and whether individual injection permits matched the federally approved record.

Agency material cited in the original article identified at least 2,553 wells permitted to inject oil-field waste or other fluids into aquifers not shown as exempt. That figure reflected the status of the review at the time; it should not be read as a current well count or as proof that every identified aquifer was contaminated.

The corrective plan

The state plan released with the disclosures proposed several steps:

• Review wells potentially injecting into non-exempt aquifers and assess groundwater risk.
• Create processes for evaluating aquifer status and proposed exemptions.
• Improve public information about exemptions and the injection-control program.
• Phase out injection into non-exempt aquifers or require an approved exemption.
• Review California’s injection-control regulations.
• Create a searchable database of Class II wells and aquifer exemptions.

Those measures addressed essential administrative failures. The central objection was timing: the proposal contemplated continued injection in some disputed aquifers while their status was being evaluated. Where the legality and safety of injection remained uncertain, continued disposal risked making any groundwater damage harder to contain.

Immediate safeguards requested

The policy argument called for regulators and elected officials to take two immediate actions:

• Halt injection into protected drinking-water aquifers until their status was confirmed and testing determined whether contamination was present.
• Review the aquifer-exemption program in light of water scarcity, treatment technology, and the increasing value of groundwater once considered marginal.

The older exemption criteria also deserved scrutiny. Water conditions and treatment capabilities change. A source dismissed as impractical decades earlier can become important as communities face scarcity and develop better treatment options. Regulatory decisions should account for that changing public value rather than treating historic assumptions as permanent.

Accountability is shared

Operators are responsible for complying with permit conditions and environmental law. State regulators are responsible for maintaining accurate records, verifying exemption boundaries, reviewing permits, and enforcing violations. The federal Environmental Protection Agency is responsible for meaningful oversight of the delegated injection-control program. When those layers fail together, the public cannot confidently determine whether groundwater is protected.

Transparency and improved recordkeeping are necessary, but they are not substitutes for monitoring and enforcement. Public-health protection requires a usable well database, mapped aquifer boundaries, disclosed test results, prompt correction of unlawful permits, and precaution when the evidence remains incomplete.