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Locating and protecting underground sources of drinking water is a critical part of addressing the long-term drinking water needs of communities across the country. It is an equally important aspect of siting  oil   and  gas injection wells, in order to avoid potential contamination  of these water sources. Oil and gas operators who are dependent on the injection of  wastewater and other fluids underground must know the location and depth of current or  future sources of drinking water in order comply with federal regulations. However, this is not always the case.

New research shows that the Oklahoma Corporation Commission (OCC) may have permitted oil and gas wells to inject into potential underground sources of drinking water that are supposed to be protected by federal law and off limits to fossil fuel activities.

This analysis of injection well locations  and water quality data indicates that the OCC may have failed to protect underground sources of drinking water (USDW)  from oil  and gas injection wells. The OCC  uses Base-of-Treatable (BTW)  water maps to define where groundwater must be  protected as USDW. However, it appears that injection well permitting has not always followed this rule.


Map of 18 oil and gas wells potentially impacting drinking water

Our analysis found that 18 oil and gas wells were permitted to inject into depths above the BTW, and do  not appear to have received aquifer exemption approval required to authorize injection. If the BTW is  accurate at these well sites, then these wells are injecting into groundwater, which could serve as a drinking water source and must be protected by the Safe Drinking Water Act.

A similar analysis comparing Oklahoma’s BTW water maps to water supply wells, reveals that 6,844 domestic water wells and 175 public water supply wells draw groundwater from below the reported BTW. Since these drinking water wells are extracting usable water, the accuracy of the BTW must be called into question.

Taken  together,  these  troubling  revelations make it clear that the BTW  is not an adequate tool alone to predict location and depth of USDWs and relying on it presents serious complications. Indeed, Oklahoma drinking water in some cases may be  at risk from oil  and gas injection wells and without a clear understanding of the locations of USDWs, the extent of the issue is unknown.


Base of Treatable Water contours across Oklahoma

Understanding the geologic terrain and ground- water quality is part of the foundation of any oil and gas regulatory agency designed to appropriately manage industrial pollution threats. In order to adequately protect USDWs going for- ward, Clean Water Action calls on Oklahoma to:

  1. Conduct a transparent review of  the full  inventory of Class II wells to determine if any additional  wells are injecting  into USDWs.
  2. Immediately halt injection activity at any wells injecting  into  USDWs without  the  required aquifer exemption.
  3. Review methods for deter- mining USDW location and depth and reevaluate the use of the BTW.
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