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Old and abandoned wells provide pathways for migration of uranium solution into underground sources of drinking water

EPA-commissioned report reveals uncertainties in defining "zone of endangering influence" from ISL wells

Posted August 15, 2007

 

 

Guidance Document for the Area of Review Requirement - Engineering Enterprises, Inc. (Norman, Oklahoma)

U.S Environmental Protection Agency - May 1985 (pdf)

 

Excerpts:

 

The Safe Drinking Water Act directs the Environmental Protection Agency (EPA) to develop minimum requirements for State programs to protect underground sources of drinking water (10,000 mg/l TDS or less) from subsurface injection of contaminants....

 

...One of the UIC regulations requires the permitting authority to determine, within an "area of review" (AOR), whether a proposed injection operation has a potential for contaminating underground sources of drinking water through wells, faults, or other pathways that penetrate an injection zone. The AOR -- also known as the zone of endangering influence -- is defined to be that area surrounding an injection well or injection well pattern in which the pressure change in the injection zone, resulting from high pressure injection, is great enough to make possible the migration of fluids out of the injection zone and into an underground source of drinking water...

 

...Potential pathways for hydraulic communication can include improperly plugged, completed, or abandoned wells that penetrate both the injection zone and fresh water zones. Figure 111-5 shows an example of fluid from the injection zone migrating upward into a fresh water aquifer through an unplugged well that penetrates the injection zone within the zone of endangering influence created by the injection operation. In this case migration occurs through the available pathway because the initial pressure of the fluid in the injection zone at the location of the pathway was raised higher than the water level in the fresh water aquifer...

 

...Other possible pathways can be fractures or faults that provide a means for hydraulic communication between the injection zone and an underground source of drinking water...

 

...Wells of all kinds -- producing or abandoned -- that penetrate the injection zone within the AOR have the potential to become pathways for migration. Whether or not they will, in fact, leak, is a function of how the wells were constructed and/or plugged...

 

...Locating possible pathways in which migration could occur, within an established AOR, is an important concept of the UIC regulations. Unfortunately, circumstances can make a realistic application of this concept difficult. For example, the location and exact status of abandoned wells may be difficult to ascertain; or there may be little confidence in completion and plugging records. These types of problems are not surprising, considering that the review process includes wells that were drilled, completed, and abandoned before adequate record keeping systems were established. Intuitively, it can be expected that in areas where there are older wells there will be an increase in the need for corrective action simply because of the methods of construction and abandonment that prevailed in earlier years. Identifying problem wells that may provide a pathway for contaminants can be a major problem to deal with when adequate information on these wells is not available...

 

...Once the AOR has been delineated, all potential pathways that may allow migration to occur should be identified during this step. All known wells that penetrate the injection zone within the AOR are required to be identified and the records of these wells checked to determine if any were improperly completed and/or abandoned. Several problems could be encountered when applying this step. First, there may be unidentifiable pathways or wells with little or no information on their completion or abandonment. Second, available records
may be inaccurate, incomplete or otherwise questionable...